[Review of] Patricia Hill Collins. Fighting Words: Black Women & The Search For Justice

Collins\u27 Fighting Words builds on her previous work, Black Feminist Thought, as she explores standpoint theory and the outsider within position and their usefulness for Black feminist thought. She structures her analysis by critiquing its effectiveness as critical social theory. For Collins, Critical social theory constitutes theorizing about the social in defense of economic and social justice. Because African American women and other oppressed groups seek economic and social justice, she posits that their social theories may generate new perspectives on injustice

Phonons in a Nanoparticle Mechanically Coupled to a Substrate

The discrete nature of the vibrational modes of an isolated nanometer-scale solid dramatically modifies its low-energy electron and phonon dynamics from that of a bulk crystal. However, nanocrystals are usually coupled--even if only weakly--to an environment consisting of other nanocrystals, a support matrix, or a solid substrate, and this environmental interaction will modify the vibrational properties at low frequencies. In this paper we investigate the modification of the vibrational modes of an insulating spherical nanoparticle caused by a weak {\it mechanical} coupling to a semi-infinite substrate. The phonons of the bulk substrate act as a bath of harmonic oscillators, and the coupling to this reservoir shifts and broadens the nanoparticle's modes. The vibrational density of states in the nanoparticle is obtained by solving the Dyson equation for the phonon propagator, and we show that environmental interaction is especially important at low frequencies. As a probe of the modified phonon spectrum, we consider nonradiative energy relaxation of a localized electronic impurity state in the nanoparticle, for which good agreement with experiment is found.Comment: 10 pages, Revte

Cavity-enhanced room-temperature magnetometry using absorption by nitrogen-vacancy centers in diamond

We demonstrate a cavity-enhanced room-temperature magnetic field sensor based on nitrogen-vacancy centers in diamond. Magnetic resonance is detected using absorption of light resonant with the 1042 nm spin-singlet transition. The diamond is placed in an external optical cavity to enhance the absorption, and significant absorption is observed even at room temperature. We demonstrate a magnetic field sensitivity of 2.5 nT/sqrt(Hz), and project a photon shot-noise-limited sensitivity of 70 pT/sqrt(Hz) for a few mW of infrared light, and a quantum projection-noise-limited sensitivity of 250 fT/sqrt(Hz) for the sensing volume of 90 um x 90 um 200 um.Comment: main text 5 pages, supplementary material 3 page

Investigation of Corrosion in Aluminum/Adhesive Lap-Splices Using Pulse-Echo Ultrasonic Techniques

Corrosion can exist in any layer of a simple aluminum/adhesive lap-splice. For lap- splices where only one aluminum surface is accessible, first layer corrosion is corrosion that occurs on or under the accessible skin; and second layer corrosion is that which exists behind the adhesive/scrim layer on the upper or lower surface of the inaccessible skin. Many different nondestructive evaluation (NDE) techniques can detect first layer corrosion, and much progress has been made quantifying corrosion that exists in this layer[l]. Due to the layered nature of a lap-splice, second layer corrosion is much more difficult to detect, and also more difficult to quantify. Current maintenance procedures also make it difficult for researchers to obtain lap-splice corrosion samples from serviceable aircraft. The detection of corrosion in lap-splice assemblies has been given an important inspection priority by the airline industry, and regular inspection procedures have been developed to meet these new requirements. During maintenance, if corrosion is suspected in a lap-splice area, the area is opened up for further inspection by removing the rivets, adhesive and sometimes the paint. If the corrosion damage is beyond the manufacturer’s tolerances, the corroded area is cut out and patch-repaired; otherwise, the corrosion is removed by chemical or mechanical means, leaving a serviceable but thinner metal skin when the joint is reassembled[2]. In either case the original character of the lap-splice has been destroyed by the maintenance process, and its use for NDE purposes is lost. In this light, it becomes necessary for researchers to fabricate their own laboratory samples and compare these artificial samples with actual in-service samples

Historical development of the financial reporting model for state and local governments in the United States from late 1800s to 1999

This study examines the historical development of the financial reporting model for state and local governments in the United States from the late 1800s through the issuance by the Governmental Accounting Standards Board (GASB) of Statement No. 34 in 1999. This research shows how the current governmental reporting standard evolved over time to meet diverse user needs by presenting both government-wide and fund statements, and requiring three governmental operating statements with potentially three different measurement focuses: the Statement of Activities; the Statement of Revenues, Expenditures, and Changes in Fund Balances; and the Budgetary Comparison Schedule. Overall, this historical study provides unique insights about the development of the governmental reporting model and an appreciation for the reporting requirements of GASB Statement No. 34

A Hubble Space Telescope Snapshot Survey of Dynamically Close Galaxy Pairs in the CNOC2 Redshift Survey

We compare the structural properties of two classes of galaxies at intermediate redshift: those in dynamically close galaxy pairs, and those which are isolated. Both samples are selected from the CNOC2 Redshift Survey, and have redshifts in the range 0.1 < z <0.6. Hubble Space Telescope WFPC2 images were acquired as part of a snapshot survey, and were used to measure bulge fraction and asymmetry for these galaxies. We find that paired and isolated galaxies have identical distributions of bulge fractions. Conversely, we find that paired galaxies are much more likely to be asymmetric (R_T+R_A >= 0.13) than isolated galaxies. Assuming that half of these pairs are unlikely to be close enough to merge, we estimate that 40% +/- 11% of merging galaxies are asymmetric, compared with 9% +/- 3% of isolated galaxies. The difference is even more striking for strongly asymmetric (R_T+R_A >= 0.16) galaxies: 25% +/- 8% for merging galaxies versus 1% +/- 1% for isolated galaxies. We find that strongly asymmetric paired galaxies are very blue, with rest-frame B-R colors close to 0.80, compared with a mean (B-R)_0 of 1.24 for all paired galaxies. In addition, asymmetric galaxies in pairs have strong [OII]3727 emission lines. We conclude that close to half of the galaxy pairs in our sample are in the process of merging, and that most of these mergers are accompanied by triggered star formation.Comment: Accepted for publication in the Astronomical Journal. 40 pages, including 15 figures. For full resolution version, please see http://www.trentu.ca/physics/dpatton/hstpairs

Dissipation due to tunneling two-level systems in gold nanomechanical resonators

We present measurements of the dissipation and frequency shift in nanomechanical gold resonators at temperatures down to 10 mK. The resonators were fabricated as doubly-clamped beams above a GaAs substrate and actuated magnetomotively. Measurements on beams with frequencies 7.95 MHz and 3.87 MHz revealed that from 30 mK to 500 mK the dissipation increases with temperature as $T^{0.5}$, with saturation occurring at higher temperatures. The relative frequency shift of the resonators increases logarithmically with temperature up to at least 400 mK. Similarities with the behavior of bulk amorphous solids suggest that the dissipation in our resonators is dominated by two-level systems

Stream network analysis and geomorphic flood plain mapping from orbital and suborbital remote sensing imagery application to flood hazard studies in central Texas

The author has identified the following significant results. Development of a quantitative hydrogeomorphic approach to flood hazard evaluation was hindered by (1) problems of resolution and definition of the morphometric parameters which have hydrologic significance, and (2) mechanical difficulties in creating the necessary volume of data for meaningful analysis. Measures of network resolution such as drainage density and basin Shreve magnitude indicated that large scale topographic maps offered greater resolution than small scale suborbital imagery and orbital imagery. The disparity in network resolution capabilities between orbital and suborbital imagery formats depends on factors such as rock type, vegetation, and land use. The problem of morphometric data analysis was approached by developing a computer-assisted method for network analysis. The system allows rapid identification of network properties which can then be related to measures of flood response

Stimulated Neutrino Transformation with Sinusoidal Density Profiles

Large amplitude oscillations between the states of a quantum system can be stimulated by sinusoidal external potentials with frequencies that are similar to the energy level splitting of the states or a fraction thereof. Situations when the applied frequency is equal to an integer fraction of the energy level splittings are known as parametric resonances. We investigate this effect for neutrinos both analytically and numerically for the case of arbitrary numbers of neutrino flavors. We look for environments where the effect may be observed and find that supernova are the one realistic possibility due to the necessity of both large densities and large amplitude fluctuations. The comparison of numerical and analytic results of neutrino propagation through a model supernova reveals it is possible to predict the locations and strengths of the stimulated transitions that occur.Comment: 14 pages, 6 figure