A chain theorem for internally 4-connected binary matroids

This is the post-print version of the Article - Copyright @ 2011 ElsevierLet M be a matroid. When M is 3-connected, Tutte’s Wheels-and-Whirls Theorem proves that M has a 3-connected proper minor N with |E(M) − E(N)| = 1 unless M is a wheel or a whirl. This paper establishes a corresponding result for internally 4-connected binary matroids. In particular, we prove that if M is such a matroid, then M has an internally 4-connected proper minor N with |E(M) − E(N)| at most 3 unless M or its dual is the cycle matroid of a planar or Möbius quartic ladder, or a 16-element variant of such a planar ladder.This study was partially supported by the National Security Agency

Towards a splitter theorem for internally 4-connected binary matroids

This is the post-print version of the Article - Copyright @ 2012 ElsevierWe prove that if M is a 4-connected binary matroid and N is an internally 4-connected proper minor of M with at least 7 elements, then, unless M is a certain 16-element matroid, there is an element e of E(M) such that either M\e or M/e is internally 4-connected having an N-minor. This strengthens a result of Zhou and is a first step towards obtaining a splitter theorem for internally 4-connected binary matroids.This study is partially funded by Marsden Fund of New Zealand and the National Security Agency

An equivalent layer magnetization model for the United States derived from MAGSAT data

Long wavelength anomalies in the total magnetic field measured field measured by MAGSAT over the United States and adjacent areas are inverted to an equivalent layer crustal magnetization distribution. The model is based on an equal area dipole grid at the Earth's surface. Model resolution having physical significance, is about 220 km for MAGSAT data in the elevation range 300-500 km. The magnetization contours correlate well with large-scale tectonic provinces

A real-time digital program for estimating aircraft stability and control parameters from flight test data by using the maximum likelihood method

A computer program (Langley program C1123) has been developed for estimating aircraft stability and control parameters from flight test data. These parameters are estimated by the maximum likelihood estimation procedure implemented on a real-time digital simulation system, which uses the Control Data 6600 computer. This system allows the investigator to interact with the program in order to obtain satisfactory results. Part of this system, the control and display capabilities, is described for this program. This report also describes the computer program by presenting the program variables, subroutines, flow charts, listings, and operational features. Program usage is demonstrated with a test case using pseudo or simulated flight data

Radar System Characterization Extended to Hardware in the Loop Simulation for the Lab-Volt™ Training System

Modeling RADAR signals in software allows the testing of potential electronic counter measures and electronic counter counter measures without the associated RADAR hardware and test facilities. Performing a characterization process on a real world RADAR system reveals all imperfections within the system. The Lab-Volt™ RADAR system served as the characterized real world RADAR system. The characterization process consisted of measurements at selected front panel locations on the Lab-Volt™ transmitter module, antenna pedestal, receiver module, and dual channel sampler module. Due to the overwhelming influence of antenna parameters on a received signal, the characterization process also attempted to derive an antenna transfer function that described how the antenna filters a signal that is passed through it. The characterization process also determined the manner in which different adjustments influenced the signal. A MatLab simulation modeled the Lab-Volt™ system operating under ideal conditions. Comparing measurements from the characterization process and the MatLab simulation placed numerical values on the imperfections in the Lab-Volt™ system. Finally, integration of the Lab-Volt ™ system explored an elementary hardware-in-the-loop configuration

Maine Community Hospitals: Providing High-Quality, Affordable Care

Mary Mayhew in this commentary provides the perspective of the Maine Hospital Association in response to a study analyzing hospital costs in Maine from 1993-2003

Poverty on the Periphery: U.S. Implementation of Modernization Theory in the Alliance for Progress and the War on Poverty

The principle objective of this paper is to compare how modernization theory was implemented during the Alliance for Progress and the War on Poverty and to explore how this impacted power structures at the national level in the Alliance and the local level in the War on Poverty There have been some earlier works which have addressed modernization theory during the Alliance for Progress, including Michael Latham\u27s, Modernization as Ideology, however most information about modernization theory itself comes from W.W. Rostow\u27s work, The Stages of Economic Growth, and Rostow and Millikan\u27s, A Proposal. During the War on Poverty, President Johnson also utilized modernization theory; though current scholarship focuses primarily on specific War on Poverty programs, such as Frank Stricker\u27s, Why America Lost the War on Poverty---And How to Win It, or on the War on Poverty in specific areas of the country, such as David Whisnant\u27s, Modernizing the Mountaineer .;While much work has been done about why the Alliance and the War on Poverty failed, there has been little looking at the connection between the two or how modernization theory impacted the making of policy. I seek to explore the relationship between these two programs and how modernization theory was put into practice in each. In this paper, I argue that due to the way in which modernization theory was used to enact both the Alliance for Progress and the War on Poverty, traditional power structures were strengthened ensuring that, in the Alliance, the goal of creating democratic governments was never reached and in the War on Poverty, the attempt to include the poor more fully in the decision making process was never attained. Additionally, I argue that the very policies which were intended to bolster the democratic process instead led to a resurfacing of dictatorships throughout Latin America and a doubling down by political machines within the local governments affected by the War on Poverty, in order to more firmly hold onto power

Isomeric effects in the gas-phase reactions of dichloroethene, C2H2Cl2, with a series of cations

A study of the reactions of a series of gas-phase cations (NH$_4^+$, H$_3$O$^+$, SF$_3^+$, CF$_3^+$, CF$^+$, SF5$^+$, SF$_2^+$, SF$^+$, CF$_2^+$, SF$_4^+$, O$_2^+$, Xe$^+$, N$_2$O$^+$, CO$_2^+$, Kr$^+$, CO$^+$, N$^+$, N$_2^+$, Ar$^+$, F$^+$ and Ne$^+$) with the three structural isomers of dichloroethene, i.e. 1,1-C$_2$H$_2$Cl$_2$, cis-1,2-C$_2$H$_2$Cl$_2$ and trans-1,2-C$_2$H$_2$Cl$_2$ is reported. The recombination energy of these ions spans the range 4.7-21.6 eV. Reaction rate coefficients and product branching ratios have been measured at 298 K in a selected ion flow tube. Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental data. Thermochemistry and mass balance have been used to predict the most feasible neutral products. Threshold photoelectron-photoion coincidence spectra have also been obtained for the three isomers of C$_2$H$_2$Cl$_2$ with photon energies in the range 10-23 eV. The fragment ion branching ratios have been compared with those of the flow tube study to determine the importance of long-range charge transfer. A strong influence of the isomeric structure of dichloroethene on the products of ion-molecule reactions has been observed for H$_3$O$^+$, CF$_3^+$, and CF$^+$. For 1,1-C$_2$H$_2$Cl$_2$ the reaction with H$_3$O$^+$ proceeds at the collisional rate with the only ionic product being 1,1-C$_2$H$_2$Cl$_2$H$^+$. However, the same reaction yields two more ionic products in the case of cis-1,2- and trans-1,2-C$_2$H$_2$Cl$_2$, but only proceeds with 14 % and 18 % efficiency, respectively. The CF$_3^+$ reaction proceeds with 56-80 % efficiency, the only ionic product for 1,1-C$_2$H$_2$Cl$_2$ being C$_2$H$_2$Cl$^+$ formed via Cl- abstraction, whereas the only ionic product for both 1,2-isomers is CHCl$_2^+$ corresponding to a breaking of the C=C double bond. Less profound isomeric effects, but still resulting in different products for 1,1- and 1,2-C$_2$H$_2$Cl$_2$ isomers, have been found in the reactions of SF$^+$, CO$_2^+$, CO$^+$, N$_2^+$, and Ar$^+$. Although these five ions have recombination energies above the ionization energy of any of the C$_2$H$_2$Cl$_2$ isomers and hence the threshold for long-range charge transfer, the results suggest that the formation of a collision complex at short range between these ions and C$_2$H$_2$Cl$_2$ is responsible for the observed effects

A Selected Ion Flow Tube Study of the Reactions of Several Cations with the Group 6B Hexafluorides SF6, SeF6, and TeF6

The first investigation of the ion chemistry of SeF$_6$ and TeF$_6$ is presented. Using a selected ion flow tube, the thermal rate coefficients and ion product distributions have been determined at 300 K for the reactions of fourteen atomic and molecular cations, namely H$_3$O$^+$, CF$_3^+$, CF$^+$, CF$_2^+$, H$_2$O$^+$, N$_2$O$^+$, O$^+$, CO$_2^+$, CO$^+$, N$^+$, N$_2^+$, Ar$^+$, F$^+$ and Ne$^+$ (in order of increasing recombination energy), with SeF$_6$ and TeF$_6$. The results are compared with those from the reactions of these ions with SF$_6$, for which the reactions with CF$^+$, CF$_2^+$, N$_2$O$^+$ and F$^+$ are reported for the first time. Several distinct processes are observed amongst the large number of reactions studied, including dissociative charge transfer, and F$^-$, F, F$_2^-$ and F$_2$ abstraction from the neutral reactant molecule to the reagent ion. The dissociative charge transfer channels are discussed in relation to vacuum ultraviolet photoelectron and threshold photoelectron-photoion coincidence spectra of XF$_6$ (X = S, Se, and Te). For reagent ions whose recombination energies lie between the first dissociative ionisation limit, XF$_6$ $\rightarrow$ XF$_5^+$ + F + e$^-$, and the onset of ionisation of the XF$_6$ molecule, the results suggest that if dissociative charge transfer occurs, it proceeds via an intimate encounter. For those reagent ions whose recombination energies are greater than the onset of ionisation, long-range electron transfer may occur depending on whether certain physical factors apply, for example non-zero Franck-Condon overlap. From the reaction kinetics, limits for the heats of formation of SeF$_4$, SeF$_5$, TeF$_4$ and TeF$_5$ at 298 K have been obtained; $\Delta_f$H$^o$(SeF$_4$) < -369 kJ mol$^{-1}$, $\Delta_f$H$^o$(SeF$_5$) < -621 kJ mol$^{-1}$, $\Delta_f$H$^o$(TeF$_4$) > -570 kJ mol$^{-1}$, and $\Delta_f$H$^o$(TeF$_5$) < -822 kJ mol$^{-1}$

Threshold photoelectron photoion coincidence spectroscopy and selected ion flow tube reactions of CHF3: comparison of product branching ratios

The threshold photoelectron and threshold photoelectron photoion coincidence spectra of CHF$_3$ in the range 13.5 – 24.5 eV have been recorded. Ion yields and branching ratios have been determined for the three fragments CF$_3^+$, CHF2$^+$ and CF$^+$. The mean kinetic energy releases into fragment ions involving either C-H or C-F bond cleavage have been measured, and compared with statistical and impulsive models. CHF$_3^+$ behaves in a non-statistical manner characteristic of the small-molecule limit, with the ground electronic state and low-lying excited states of CHF$_3^+$ being largely repulsive along the C-H and C-F coordinates, respectively. The rate coefficients and product ion branching ratios have been measured at 298 K in a selected ion flow tube for the reactions of CHF$_3$ with a large number of gas-phase cations whose recombination energies span the range 6.3 through 21.6 eV. A comparison between the branching ratios from the two experiments, together with an analysis of the threshold photoelectron spectrum of CHF$_3$, shows that long-range charge transfer probably occurs for the Ar$^+$ and F$^+$ atomic ions whose recombination energies lie above ca. 15 eV. Below this energy, the mechanism involves a combination of short-range charge transfer and chemical reactions involving a transition state intermediate