Curve segmentation using directional information, relation to pattern detection

©2005 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.Presented at the 2005 International Conference on Image Processing (ICIP)September 11-14, 2005, Genova, Italy.DOI: 10.1109/ICIP.2005.1530175We propose an extension of the conformal (or geodesic) active contour framework in which the conformal factor depends not only on the position of the curve but also on the direction of its tangent. We describe several properties for variational curve segmentation schemes that justify the construction of optimal conformal factors (i.e., learning) in strong connection with pattern matching. The determination of optimal curves (i.e., segmentation) can be performed using either the calculus of variations or dynamic programming. The technique is illustrated on a road detection problem for different signal to noise ratios

Semiconservative Replication in the Quasispecies Model

This paper extends Eigen's quasispecies equations to account for the semiconservative nature of DNA replication. We solve the equations in the limit of infinite sequence length for the simplest case of a static, sharply peaked fitness landscape. We show that the error catastrophe occurs when $\mu$, the product of sequence length and per base pair mismatch probability, exceeds $2 \ln \frac{2}{1 + 1/k}$, where $k > 1$ is the first order growth rate constant of the viable ``master'' sequence (with all other sequences having a first-order growth rate constant of $1$). This is in contrast to the result of $\ln k$ for conservative replication. In particular, as $k \to \infty$, the error catastrophe is never reached for conservative replication, while for semiconservative replication the critical $\mu$ approaches $2 \ln 2$. Semiconservative replication is therefore considerably less robust than conservative replication to the effect of replication errors. We also show that the mean equilibrium fitness of a semiconservatively replicating system is given by $k (2 e^{-\mu/2} - 1)$ below the error catastrophe, in contrast to the standard result of $k e^{-\mu}$ for conservative replication (derived by Kimura and Maruyama in 1966).Comment: 15 pages, 7 figures, to be submitted to Phys. Rev.

Finsler Active Contours

©2008 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or distribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE. This material is presented to ensure timely dissemination of scholarly and technical work. Copyright and all rights therein are retained by authors or by other copyright holders. All persons copying this information are expected to adhere to the terms and constraints invoked by each author's copyright. In most cases, these works may not be reposted without the explicit permission of the copyright holder.DOI: 10.1109/TPAMI.2007.70713In this paper, we propose an image segmentation technique based on augmenting the conformal (or geodesic) active contour framework with directional information. In the isotropic case, the euclidean metric is locally multiplied by a scalar conformal factor based on image information such that the weighted length of curves lying on points of interest (typically edges) is small. The conformal factor that is chosen depends only upon position and is in this sense isotropic. Although directional information has been studied previously for other segmentation frameworks, here, we show that if one desires to add directionality in the conformal active contour framework, then one gets a well-defined minimization problem in the case that the factor defines a Finsler metric. Optimal curves may be obtained using the calculus of variations or dynamic programming-based schemes. Finally, we demonstrate the technique by extracting roads from aerial imagery, blood vessels from medical angiograms, and neural tracts from diffusion-weighted magnetic resonance imagery

Semiconservative replication in the quasispecies model

This is the publisher's version, also available electronically from http://journals.aps.org/pre/abstract/10.1103/PhysRevE.69.061916.This paper extends Eigen’s quasispecies equations to account for the semiconservative nature of DNA replication. We solve the equations in the limit of infinite sequence length for the simplest case of a static, sharply peaked fitness landscape. We show that the error catastrophe occurs when μ, the product of sequence length and per base pair mismatch probability, exceeds 2ln[2∕(1+1∕k)], where k>1 is the first-order growth rate constant of the viable “master” sequence (with all other sequences having a first-order growth rate constant of 1). This is in contrast to the result of lnk for conservative replication. In particular, as k→∞, the error catastrophe is never reached for conservative replication, while for semiconservative replication the critical μ approaches 2ln2. Semiconservative replication is therefore considerably less robust than conservative replication to the effect of replication errors. We also show that the mean equilibrium fitness of a semiconservatively replicating system is given by k(2e−μ∕2−1) below the error catastrophe, in contrast to the standard result of ke−μ for conservative replication (derived by Kimura and Maruyama in 1966). From this result it is readily shown that semiconservative replication is necessary to account for the observation that, at sufficiently high mutagen concentrations, faster replicating cells will die more quickly than more slowly replicating cells. Thus, in contrast to Eigen’s original model, the semiconservative quasispecies equations are able to provide a mathematical basis for explaining the efficacy of mutagens as chemotherapeutic agents

Equilibrium Distribution of Mutators in the Single Fitness Peak Model

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.91.138105.This Letter develops an analytically tractable model for determining the equilibrium distribution of mismatch repair deficient strains in unicellular populations. The approach is based on the single fitness peak model, which has been used in Eigen’s quasispecies equations in order to understand various aspects of evolutionary dynamics. As with the quasispecies model, our model for mutator-nonmutator equilibrium undergoes a phase transition in the limit of infinite sequence length. This “repair catastrophe” occurs at a critical repair error probability of ϵr=Lvia/L, where Lvia denotes the length of the genome controlling viability, while L denotes the overall length of the genome. The repair catastrophe therefore occurs when the repair error probability exceeds the fraction of deleterious mutations. Our model also gives a quantitative estimate for the equilibrium fraction of mutators in Escherichia coli

Does Eviction Cause Poverty? Quasi-Experimental Evidence from Cook County, IL

Each year, more than two million U.S. households have an eviction case filed against them. Many cities have recently implemented policies aimed at reducing the number of evictions, motivated by research showing strong associations between being evicted and subsequent adverse economic outcomes. Yet it is difficult to determine to what extent those associations represent causal relationships, because eviction itself is likely to be a consequence of adverse life events. This paper addresses that challenge and offers new causal evidence on how eviction affects financial distress, residential mobility, and neighborhood quality. We collect the near-universe of Cook County court records over a period of seventeen years, and link these records to credit bureau and payday loans data. Using this data, we characterize the trajectory of financial strain in the run-up and aftermath of eviction court for both evicted and non-evicted households, finding high levels and striking increases in financial strain in the years before an eviction case is filed. Guided by this descriptive evidence, we employ two approaches to draw causal inference on the effect of eviction. The first takes advantage of the panel data through a difference-in-differences design. The second is an instrumental variables strategy, relying on the fact that court cases are randomly assigned to judges of varying leniency. We find that eviction negatively impacts credit access and durable consumption for several years. However, the effects are small relative to the financial strain experienced by both evicted and non-evicted tenants in the run-up to an eviction filing

The motivated use of moral principles

Abstract Five studies demonstrated that people selectively use general moral principles to rationalize preferred moral conclusions. In Studies 1a and 1b, college students and community respondents were presented with variations on a traditional moral scenario that asked whether it was permissible to sacrifice one innocent man in order to save a greater number of people. Political liberals, but not relatively more conservative participants, were more likely to endorse consequentialism when the victim had a stereotypically White American name than when the victim had a stereotypically Black American name. Study 2 found evidence suggesting participants believe that the moral principles they are endorsing are general in nature: when presented sequentially with both versions of the scenario, liberals again showed a bias in their judgments to the initial scenario, but demonstrated consistency thereafter. Study 3 found conservatives were more likely to endorse the unintended killing of innocent civilians when Iraqis civilians were killed than when Americans civilians were killed, while liberals showed no significant effect. In Study 4, participants primed with patriotism were more likely to endorse consequentialism when Iraqi civilians were killed by American forces than were participants primed with multiculturalism. However, this was not the case when American civilians were killed by Iraqi forces. Implications for the role of reason in moral judgment are discussed

Development and Test of Highly Autonomous Unmanned Aerial Vehicles

Published in Journal of Aerospace Computing, Information, and Communication, Vol. 1, Issue 12, December 2004.This paper describes the design, development, and testing of Unmanned Aerial Vehicles (UAV) with highly automated search capabilities. Here, systems are able to respond on their own in the presence of considerable uncertainty utilizing an image processor, tracker/mapper, mission manager, and trajectory generation; and are used to complete a realistic benchmark reconnaissance mission. Subsequent to the selection of the search area, all functions are automated and human operator assistance is not required. The applications of these capabilities include reduction of operator workload in operational UAV systems, new UAV or guided-munition missions conducted without the assistance or availability of human operators, or the enhancement/augmentation of human search capabilities. The resulting system was able to search the 15-building village automatically with speed comparable to a human operator searching on foot or with a conventional remotely piloted vehicle. It was successful in 6 of 7 actual flights over the McKenna Military Operations in Urban Terrain test site over two different days and a variety of lighting conditions and choice of desired building

The Grizzly, October 18, 1985

Limerick: The Main Objective - Calm • Typesetting Equipment Offers New Experience • Letters: Ex-Rover Responds; Some Housing Needs Help; Reply for Sluggo • Financial Aid Striving to the Top • Search of Success Finds Bravo • Look Out for the Candid Cameras • Sorority Pledging Sees Light Through Tunnel • Field Hockey Battles Tough Competition • Booters Find Easier Times • Ultimate Frisbee is Here • Doleniak: Flying Higher Through the Sky • Grizzlies are Defeated • Campus Security Noteshttps://digitalcommons.ursinus.edu/grizzlynews/1148/thumbnail.jp