X-ray Variability and Emission Process of the Radio Jet in M87

We monitored the M87 jet with the ACIS-S detector on Chandra with 5 observations between 2002 Jan and 2002 Jul. Our goal was to determine the presence and degree of variability in morphology, intensity, and spectral parameters. We find strong variability of the core and HST-1, the knot lying 0.8" from the core. These observations were designed to constrain the X-ray emission process: whereas synchrotron emission would necessitate the presence of extremely high energy electrons with a halflife of a few years or less, inverse Compton emission from a relativistic jet would arise from low energy electrons with very long halflives. Currently, all indications point to a synchrotron process for the X-ray emission from the M87 jet. We give key parameters for a ``modest beaming'' synchrotron model.Comment: 4 pages with 2 embedded figures (1 in color). To be published in the proceedings of the Bologna Jet Workshop "The Physics of Relativistic Jets in the CHANDRA and XMM Era", 23-27 September 2002, Brunetti, Harris, Sambruna, and Setti, editors. 2003, New Ast. Re

Inverse Medea as a Novel Gene Drive System for Local Population Replacement: A Theoretical Analysis

One strategy to control mosquito-borne diseases, such as malaria and dengue fever, on a regional scale is to use gene drive systems to spread disease-refractory genes into wild mosquito populations. The development of a synthetic Medea element that has been shown to drive population replacement in laboratory Drosophila populations has provided encouragement for this strategy but has also been greeted with caution over the concern that transgenes may spread into countries without their consent. Here, we propose a novel gene drive system, inverse Medea, which is strong enough to bring about local population replacement but is unable to establish itself beyond an isolated release site. The system consists of 2 genetic components—a zygotic toxin and maternal antidote—which render heterozygous offspring of wild-type mothers unviable. Through population genetic analysis, we show that inverse Medea will only spread when it represents a majority of the alleles in a population. The element is best located on an autosome and will spread to fixation provided any associated fitness costs are dominant and to very high frequency otherwise. We suggest molecular tools that could be used to build the inverse Medea system and discuss its utility for a confined release of transgenic mosquitoes

X-ray Emission from the 3C 273 Jet

We present results from four recent Chandra monitoring observations of the jet in 3C 273 using the ACIS detector, obtained between November 2003 and July 2004. We find that the X-ray emission comes in two components: unresolved knots that are smaller than the corresponding optically emitting knots and a broad channel that is about the same width as the optical interknot region. We compute the jet speed under the assumption that the X-ray emission is due to inverse Compton scattering of the cosmic microwave background, finding that the dimming of the jet X-ray emission to the jet termination relative to the radio emission may be due to bulk deceleration.Comment: 2 pages, 2 figures, to appear in the proceedings of "The X-ray Universe 2005", San Lorenzo de El Escorial (Spain), 26-30 September 200

X-ray Emission Processes in Extragalactic Jets, Lobes and Hot Spots

This paper is a brief review of the processes responsible for X-ray emission from radio jets, lobes and hot spots. Possible photons in inverse Compton scattering models include the radio synchrotron radiation itself (i.e. synchrotron self-Compton [SSC] emission), the cosmic microwave background (CMB), the galaxy starlight and radiation from the active nucleus. SSC emission has been detected from a number of hot spots. Scattering of the CMB is expected to dominate for jets (and possibly hot spots) undergoing bulk relativistic motion close to the direction towards the observer. Scattering of infrared radiation from the AGN should be observable from radio lobes, especially if they are close to the active nucleus. Synchrotron radiation is detected in some sources, most notably the jet of M87. I briefly discuss why different hot spots emit X-rays by different emission mechanisms and the nature of the synchrotron spectra.Comment: To be published in the proceedings of the Bologna conference ``The Physics of Relativistic Jets in the Chandra and XMM Era'', New Astronomy Revie

Singlets and reflection symmetric spin systems

We rigorously establish some exact properties of reflection symmetric spin systems with antiferromagnetic crossing bonds: At least one ground state has total spin zero and a positive semidefinite coefficient matrix. The crossing bonds obey an ice rule. This augments some previous results which were limited to bipartite spin systems and is of particular interest for frustrated spin systems.Comment: 11 pages, LaTeX 2

Review of \u3cem\u3eThe Loyal West: Civil War and Reunion in Middle America\u3c/em\u3e by Matthew E. Stanley

Interest in Civil War memory and post–Civil War sectional reconciliation has expanded greatly in recent years, as two 2016 historiographical essays attest.1 Matthew E. Stanley\u27s new book, The Loyal West: Civil War and Reunion in Middle America is thus well timed to make an important contribution to our evolving understanding of the process of sectional reconciliation in the decades following the Civil War. With his focus on Kentucky\u27s northern neighbors in the lower portions of Illinois, Indiana, and Ohio, the editorial staff of the Register of the Kentucky Historical Society believe Stanley\u27s book will help historians better understand the role Kentucky played in the events of the late nineteenth and early twentieth century, which saw a white supremacist version of Civil War memory eclipse an emancipationist version nationally. We have asked four nineteenth-century historians to consider Stanley\u27s book from varying perspectives. M. Keith Harris teaches history at a private high school in Los Angeles, California. He is the author of Across the Bloody Chasm: The Culture of Commemoration among Civil War Veterans (2014) and is currently writing a book on D. W. Griffith\u27s controversial 1915 silent film, The Birth of a Nation. Anne E. Marshall is an associate professor of history at Mississippi State University and the author of Creating a Confederate Kentucky: The Lost Cause and Civil War Memory in a Border State (2012). James Marten is professor and chair of the history department at Marquette University. His most recent books are Sing Not War: The Lives of Union and Confederate Veterans in Gilded Age America (2011) and America\u27s Corporal: James Tanner in War and Peace (2014). Kristopher Maulden is a visiting assistant professor of history at Columbia College in Missouri. He is completing a book manuscript on the influence of Federalist politics and federal policy in the Ohio River Valley, and he is engaged in a study of nineteenth-century Ohio newspaper editor Charles Hammond. Finally, the author of The Loyal West, Matthew E. Stanley, assistant professor of history at Albany State University, will respond to the reviews

Around the table: Are multiple-touch surfaces better than single-touch for children's collaborative interactions?

This paper presents a classroom study that investigated the potential of using touch tabletop technology to support children's collaborative learning interactions. Children aged 7-10 worked in groups of three on a collaborative planning task in which they designed a seating plan for their classroom. In the single-touch condition, the tabletop surface allowed only one child to interact with the digital content at a time. In the multiple-touch condition, the children could interact with the digital content simultaneously. Results showed that touch condition did not affect the frequency or equity of interactions, but did influence the nature of children's discussion. In the multiple-touch condition, children talked more about the task; in the single-touch condition, they talked more about turn taking. We also report age and gender differences

Young men and gambling in the ACT: an exploratory study of attitudes, perceptions and engagement.

This report presents key findings of a 2005 study into the attitudes towards, perceptions of and engagement with gambling by young males (aged 18 – 25 years) in the Australian Capital Territory (ACT). The study is based primarily on in-depth semi-structured interviews with a sample of young males resident in the ACT

Predicting pilot error on the flight deck: Validation of a new methodology and a multiple methods and analysts approach to enhancing error prediction sensitivity

The Human Error Template (HET) is a recently developed methodology for predicting designed induced pilot error. This article describes a validation study undertaken to compare the performance of HET against three contemporary Human Error Identification (HEI) approaches when used to predict pilot errors for an approach and landing task and also to compare individual analyst error predictions to an approach to enhancing error prediction sensitivity: the multiple analysts and methods approach, whereby multiple analyst predictions using a range of HEI technique are pooled. The findings indicate that, of the four methodologies used in isolation, analysts using the HET methodology offered the most accurate error predictions, and also that the multiple analysts and methods approach was more successful overall in terms of error prediction sensitivity than the three other methods but not the HET approach. The results suggest that when predicting design induced error, it is appropriate to use domain specific approaches and also a toolkit of different HEI approaches and multiple analysts in order to heighten error prediction sensitivity

Scaling of Splay and Total Rigidity for Elastic Percolation on the Triangular Lattice

The randomly diluted elastic network with central force interactions is simulated on the triangular lattice using a constraint analysis of cluster displacement vectors. The exponents for the percolation of splay and total rigidity are found to be the same, ν=1.14±0.1, γ=1.6±0.3, and β=0.46±0.4. The concentration of bonds that are in clusters rigid only with respect to a splay deformation is evaluated as a function of bond concentration. The area under the resulting distribution diminishes with lattice size as ∼L−1.1, indicating that splay and total rigidity have the same threshold, pc≊0.64