Procedure for generating global atmospheric engine emissions data from future supersonic transport aircraft. The 1990 high speed civil transport studies

The input for global atmospheric chemistry models was generated for baseline High Speed Civil Transport (HSCT) configurations at Mach 1.6, 2.2, and 3.2. The input is supplied in the form of number of molecules of specific exhaust constituents injected into the atmosphere per year by latitude and by altitude (for 2-D codes). Seven exhaust constituents are currently supplied: NO, NO2, CO, CO2, H2O, SO2, and THC (Trace Hydrocarbons). An eighth input is also supplied, NO(x), the sum of NO and NO2. The number of molecules of a given constituent emitted per year is a function of the total fuel burned by a supersonic fleet and the emission index (EI) of the aircraft engine for the constituent in question. The EIs for an engine are supplied directly by the engine manufacturers. The annual fuel burn of a supersonic fleet is calculated from aircraft performance and economic criteria, both of which are strongly dependent on basic design parameters such as speed and range. The altitude and latitude distribution of the emission is determined based on 10 Intern. Air Transport Assoc. (IATA) regions chosen to define the worldwide route structure for future HSCT operations and the mission flight profiles

Low temperature terahertz spectroscopy of n-InSb through a magnetic field driven metal-insulator transition

We use fiber-coupled photoconductive emitters and detectors to perform terahertz (THz) spectroscopy of lightly-doped n-InSb directly in the cryogenic (1.5 K) bore of a high-field superconducting magnet. We measure transmission spectra from 0.1-1.1 THz as the sample is driven through a metal-insulator transition (MIT) by applied magnetic field. In the low-field metallic state, the data directly reveal the plasma edge and magneto-plasmon modes. With increasing field, a surprisingly broad band (0.3-0.8 THz) of low transmission appears at the onset of the MIT. This band subsequently collapses and evolves into the sharp 1s -> 2p- transition of electrons `frozen' onto isolated donors in the insulating state.Comment: 4 pages, 3 figure

A method for inverting ratio–ratio data to estimate end-member compositions in mixing problems

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Chemical Geology 352 (2013): 63–69, doi:10.1016/j.chemgeo.2013.06.002.I discuss the general problem of fitting mixing models to ratio-ratio data, and derive formulae for applying non-linear Maximum Likelihood methods for parameter estimation. To estimate mixing model parameters in the under-determined inversion it is necessary to introduce prior constraints, which I implement by penalizing the likelihood function for variations from a starting model. I illustrate practical aspects of the inverse problem by applying the method to synthetic data for a ternary system of putative mantle reservoirs using Sr, Nd, and Pb isotope ratios. I fit the synthetic data using two different starting models to demonstrate the sensitivity of the gradient method used to solve the non-linear inverse to the starting model and the necessity of inspecting the final model to avoid spurious results. I include Matlab scripts to facilitate starting model selection and to perform binary and ternary ratio-ratio inversions as an Electronic Appendix

On dynamical gluon mass generation

The effective gluon propagator constructed with the pinch technique is governed by a Schwinger-Dyson equation with special structure and gauge properties, that can be deduced from the correspondence with the background field method. Most importantly the non-perturbative gluon self-energy is transverse order-by-order in the dressed loop expansion, and separately for gluonic and ghost contributions, a property which allows for a meanigfull truncation. A linearized version of the truncated Schwinger-Dyson equation is derived, using a vertex that satisfies the required Ward identity and contains massless poles. The resulting integral equation, subject to a properly regularized constraint, is solved numerically, and the main features of the solutions are briefly discussed.Comment: Special Article - QNP2006: 4th International Conference on Quarks and Nuclear Physics, Madrid, Spain, 5-10 June 200

A Phenomenological Study of the Student Engagement Experiences of African Americans Formerly Attending Urban Public High Schools

The purpose of this hermeneutic phenomenological study was to interpret the student engagement experiences of African Americans formerly attending urban public high schools in a major city in the Mid-Atlantic region of the United States. Self-determination theory, established by Ryan and Deci (1985), is the theoretical framework for this study, and was used to understand motivation in terms of basic psychological needs satisfaction and fulfillment, and how those motivations influence human behavior. The central research question was: What were the student engagement experiences of African Americans formerly attending urban public high schools? The three research sub-questions were: (1) what instructional experiences did African Americans attribute to their student engagement experiences, (2) what interpersonal experiences did African Americans attribute to their student engagement experiences, and (3) what environmental experiences did African Americans attribute to their student engagement experiences? Qualitative questionnaires, focus groups, and semi-structured interviews were used to collect data from 12 participants selected using homogenous and snowball sampling. Data analysis was conducted using van Manes’ approach (1990) of reflecting on significant participant statements, developing thematic meaning units, and constructing textual and structural written descriptions of student engagement, concluding with a written composite interpretation of the lived experiences of the participants. The essential themes identified in the study were Engagement Experiences, Instructional Considerations, Relationships, School-Related Experiences, and Non-School-Related Factors. Participants identified the satisfaction of psychological need as the cornerstone of student engagement and as essential factor in mitigating student disengagement

Mesoscopic Capacitance Oscillations

We examine oscillations as a function of Fermi energy in the capacitance of a mesoscopic cavity connected via a single quantum channel to a metallic contact and capacitively coupled to a back gate. The oscillations depend on the distribution of single levels in the cavity, the interaction strength and the transmission probability through the quantum channel. We use a Hartree-Fock approach to exclude self-interaction. The sample specific capacitance oscillations are in marked contrast to the charge relaxation resistance, which together with the capacitance defines the RC-time, and which for spin polarized electrons is quantized at half a resistance quantum. Both the capacitance oscillations and the quantized charge relaxation resistance are seen in a strikingly clear manner in a recent experiment.Comment: 9 pages, 2 figure

A general inversion for end-member ratios in binary mixing systems

Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 6 (2005): Q11007, doi:10.1029/2005GC000975.Binary mixing is one of the most common models used to explain variations in geochemical data. When the data being modeled are ratios of elements or isotopes, the mixtures follow hyperbolic trends with curvatures that depend on a cross-term representing the relative concentrations of the elements or isotopes under consideration in the mixing components. The inverse problem of estimating mixing components is difficult because of the cross-term in the hyperbolic equation, which requires the use of nonlinear methods to estimate the mixing parameters, and because the end-member ratio values are intrinsically underdetermined unless the mixing proportions of the samples are known a priori, which is not generally the case. I use maximum likelihood methods to address these issues and derive a general inversion for binary mixing model parameters from ratio-ratio data. I apply the method to synthetic test data and a global compilation of 230Th/232Th versus 87Sr/86Sr data from oceanic basalts and find that the concentration ratio parameter is well-constrained by the inversion while the end-member ratio estimates are strongly dependent on the initial guesses used to start the iterative solver, reflecting the underdetermined nature of the end-member positions on the mixing hyperbola. Monte Carlo methods that randomly perturb the initial guesses can be used to improve error estimates, and goodness-of-fit statistics can be used to assess the performance of the mixing model for explaining data variance