Inverse Bremsstrahlung in Shocked Astrophysical Plasmas

There has recently been interest in the role of inverse bremsstrahlung, the emission of photons by fast suprathermal ions in collisions with ambient electrons possessing relatively low velocities, in tenuous plasmas in various astrophysical contexts. This follows a long hiatus in the application of suprathermal ion bremsstrahlung to astrophysical models since the early 1970s. The potential importance of inverse bremsstrahlung relative to normal bremsstrahlung, i.e. where ions are at rest, hinges upon the underlying velocity distributions of the interacting species. In this paper, we identify the conditions under which the inverse bremsstrahlung emissivity is significant relative to that for normal bremsstrahlung in shocked astrophysical plasmas. We determine that, since both observational and theoretical evidence favors electron temperatures almost comparable to, and certainly not very deficient relative to proton temperatures in shocked plasmas, these environments generally render inverse bremsstrahlung at best a minor contributor to the overall emission. Hence inverse bremsstrahlung can be safely neglected in most models invoking shock acceleration in discrete sources such as supernova remnants. However, on scales > 100pc distant from these sources, Coulomb collisional losses can deplete the cosmic ray electrons, rendering inverse bremsstrahlung, and perhaps bremsstrahlung from knock-on electrons, possibly detectable.Comment: 13 pages, including 2 figures, using apjgalley format; to appear in the January 10, 2000 issue, of the Astrophysical Journa

The Impact of Tobacco Control Program Expenditures on Aggregate Cigarette Sales: 1981-1998

Since the 1998 Master Settlement Agreement between states and the tobacco industry, states have unprecedented resources for programs to reduce tobacco use. Decisions concerning the use of these funds will, in part, be based on the experiences of states with existing programs. We review the experiences of several states that have adopted comprehensive tobacco control programs. We also report estimates from econometric analyses of the impact of tobacco control expenditures on aggregate tobacco use in all states and in selected states with comprehensive programs for the period from 1981 through 1998. Our analyses clearly show that increases in funding for state tobacco control programs reduce tobacco use.

“You Got To Know Us”: A Hopeful Model for Music Education in Urban Schools

Urban schools, and the students and teachers within, are often characterized by a metanarrative of deficit and crisis, causing the complex realities of urban education to remain unclear behind a wall of assumptions and stereotypes. Within music education, urban schools have received limited but increasing attention from researchers. However, voices from practitioners are often missing from this dialogue, and the extant scholarly dialogue has had a very limited effect on music teacher education. In this article, five music educators with a combined thirty years of experience in urban schools examine aspects of their experiences in the light of critical pedagogy in an attempt to disrupt the metanarrative of deficit, crisis, and decline that continues to surround urban music education. By promoting the lived-stories of successful urban music students, teachers, and programs, the authors hope to situate urban music education as a site of renewal, reform, and meaningful learning. This paper emerged from a panel discussion regarding promising practices in secondary general music with urban youth that took place at the New Directions in Music Education conference held at Michigan State University in October of 2011

Engaging the articulators enhances perception of concordant visible speech movements

PURPOSE This study aimed to test whether (and how) somatosensory feedback signals from the vocal tract affect concurrent unimodal visual speech perception. METHOD Participants discriminated pairs of silent visual utterances of vowels under 3 experimental conditions: (a) normal (baseline) and while holding either (b) a bite block or (c) a lip tube in their mouths. To test the specificity of somatosensory-visual interactions during perception, we assessed discrimination of vowel contrasts optically distinguished based on their mandibular (English /ɛ/-/æ/) or labial (English /u/-French /u/) postures. In addition, we assessed perception of each contrast using dynamically articulating videos and static (single-frame) images of each gesture (at vowel midpoint). RESULTS Engaging the jaw selectively facilitated perception of the dynamic gestures optically distinct in terms of jaw height, whereas engaging the lips selectively facilitated perception of the dynamic gestures optically distinct in terms of their degree of lip compression and protrusion. Thus, participants perceived visible speech movements in relation to the configuration and shape of their own vocal tract (and possibly their ability to produce covert vowel production-like movements). In contrast, engaging the articulators had no effect when the speaking faces did not move, suggesting that the somatosensory inputs affected perception of time-varying kinematic information rather than changes in target (movement end point) mouth shapes. CONCLUSIONS These findings suggest that orofacial somatosensory inputs associated with speech production prime premotor and somatosensory brain regions involved in the sensorimotor control of speech, thereby facilitating perception of concordant visible speech movements. SUPPLEMENTAL MATERIAL https://doi.org/10.23641/asha.9911846R01 DC002852 - NIDCD NIH HHSAccepted manuscrip

Direct Acceleration of Pickup Ions at The Solar Wind Termination Shock: The Production of Anomalous Cosmic Rays

We have modeled the injection and acceleration of pickup ions at the solar wind termination shock and investigated the parameters needed to produce the observed Anomalous Cosmic Ray (ACR) fluxes. A non-linear Monte Carlo technique was employed, which in effect solves the Boltzmann equation and is not restricted to near-isotropic particle distribution functions. This technique models the injection of thermal and pickup ions, the acceleration of these ions, and the determination of the shock structure under the influence of the accelerated ions. The essential effects of injection are treated in a mostly self-consistent manner, including effects from shock obliquity, cross- field diffusion, and pitch-angle scattering. Using recent determinations of pickup ion densities, we are able to match the absolute flux of hydrogen in the ACRs by assuming that pickup ion scattering mean free paths, at the termination shock, are much less than an AU and that modestly strong cross-field diffusion occurs. Simultaneously, we match the flux ratios He(+)/H(+) or O(+)/H(+) to within a factor approx. 5. If the conditions of strong scattering apply, no pre-termination-shock injection phase is required and the injection and acceleration of pickup ions at the termination shock is totally analogous to the injection and acceleration of ions at highly oblique interplanetary shocks recently observed by the Ulysses spacecraft. The fact that ACR fluxes can be modeled with standard shock assumptions suggests that the much-discussed "injection problem" for highly oblique shocks stems from incomplete (either mathematical or computer) modeling of these shocks rather than from any actual difficulty shocks may have in injecting and accelerating thermal or quasi-thermal particles

Non-linear Particle Acceleration in Oblique Shocks

We have developed a Monte Carlo technique for self-consistently calculating the hydrodynamic structure of oblique, steady-state shocks, together with the first-order Fermi acceleration process and associated non-thermal particle distributions. This is the first internally consistent treatment of modified shocks that includes cross-field diffusion of particles. Our method overcomes the injection problem faced by analytic descriptions of shock acceleration, and the lack of adequate dynamic range and artificial suppression of cross-field diffusion faced by plasma simulations; it currently provides the most broad and versatile description of collisionless shocks undergoing efficient particle acceleration. We present solutions for plasma quantities and particle distributions upstream and downstream of shocks, illustrating the strong differences observed between non-linear and test-particle cases. It is found that there are only marginal differences in the injection efficiency and resultant spectra for two extreme scattering modes, namely large-angle scattering and pitch-angle diffusion, for a wide range of shock parameters, i.e., for subluminal shocks with field obliquities less than or equal to 75 degrees and de Hoffmann-Teller frame speeds much less than the speed of light.Comment: 38 pages, 15 figures, AASTeX format, to appear in the Astrophysical Journal, December 20, 199

Do Higher Cigarette Prices Encourage Youth to Use Marijuana?

Every major national tobacco legislation proposed in the past two years has called for significant increases in the price of cigarettes as a way to discourage youths from smoking. One argument used to oppose these bills is that increases in the price of cigarettes would cause youths to substitute marijuana for cigarettes. Although it has long been believed that cigarettes are a gateway drug,' no economic research has been done to determine whether cigarettes and marijuana are economic complements or substitutes. This paper begins to fill the void in the current research by examining the contemporaneous relationship between the demands for cigarettes and marijuana among a nationally representative sample of 8th, 10th and 12th graders from the 1992-1994 Monitoring the Future Project. Two part models are used to estimate reduced form demand equations. Examination of the cross-price effects clearly shows that higher cigarette prices will not increase marijuana use among youths. In addition to reducing youth smoking, we find that higher cigarette prices significantly reduce the average level of marijuana used by current users. Cigarette prices also have a negative effect on the probability of using marijuana findings are not significant at conventional levels.

Recertification and Reentry to Practice for Nurse Anesthetists: Determining Core Competencies and Evaluating Performance via High-Fidelity Simulation Technology

Introduction The National Board of Certification and Recertification for Nurse Anesthetistsaddressed a barrier to return to practice of uncertified practitioners by replacing required direct patient care experiences with high-fidelity simulation. Objectives The aims of this study were to: (a) validate a set of clinical activities for their relevance to reentry and determine if they could be replicated using simulation, (b) evaluate the content validity of an existing simulation scenario containing the proposed clinical activities and determine its substitutability for a clinical practicum, and (c) evaluate the validity of two methods to assess simulation performance. Methods A modified Delphi method incorporating an autonomous, anonymous, three-round online survey process using three unique expert certified registered nurse anesthetists groups was used to address each study aim. Results Twenty-seven clinical activities gained consensus as necessary to be assessed in the simulation. All 14 survey questions used to determine simulation content validity exceeded the minimum content validity index (CVI) value of 0.78, with a mean CVI of 0.99. The global rating scale CVI and the competency checklist CVI were 0.83 and 1.0, respectively. Conclusion The findings add to the existing literature supporting the utility of simulation for high-stakes provider assessment and certification