Anisotropic Thermal Conduction in Supernova Remnants: Relevance to Hot Gas Filling Factors in the Magnetized ISM

We explore the importance of anisotropic thermal conduction in the evolution of supernova remnants via numerical simulations. The mean temperature of the bubble of hot gas is decreased by a factor of ~3 compared to simulations without thermal conduction, together with an increase in the mean density of hot gas by a similar factor. Thus, thermal conduction greatly reduces the volume of hot gas produced over the life of the remnant. This underscores the importance of thermal conduction in estimating the hot gas filling fraction and emissivities in high-stage ions in Galactic and proto-galactic ISMs.Comment: Submitted to Astrophysical Journal Letters. 4 pages, 3 figure

Teaching Innovation as Part of an Agribusiness Curriculum

Innovation is critical to the survival of agricultural businesses in the U.S. yet few universities have classes in their curricula that focus on innovation and innovation management. Innovation includes developing new processes and concepts and taking products based on those ideas to market. By its nature, innovation generally involves technical components, market assessment, business analysis, and implementation strategies that include marketing campaigns to a target market. As a result, if innovation is going to be experientially taught to students, the class will likely need to include concepts from multiple disciplines. The objectives of this paper are to present an outline of capstone/senior design classes designed to cause students to learn innovation by participating in interdisciplinary teams working with real companies on the development of new product innovation.Teaching/Communication/Extension/Profession,

Dust Stratification in Young Circumstellar Disks

We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O as well as broad emission lines of gas phase12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line of sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas to dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling and grain growth to explain the results. The techniques presented here allow us to provide some observationally-motivated bounds on accretion disk alpha in protostellar systems

Direct Evidence for Two-Fluid Effects in Molecular Clouds

We present a combination of theoretical and simulation-based examinations of the role of two-fluid ambipolar drift on molecular line widths. The dissipation provided by ion-neutral interactions can produce a significant difference between the widths of neutral molecules and the widths of ionic species, comparable to the sound speed. We demonstrate that Alfven waves and certain families of magnetosonic waves become strongly damped on scales comparable to the ambipolar diffusion scale. Using the RIEMANN code, we simulate two-fluid turbulence with ionization fractions ranging from 10^{-2} to 10^{-6}. We show that the wave damping causes the power spectrum of the ion velocity to drop below that of the neutral velocity when measured on a relative basis. Following a set of motivational observations by Li & Houde (2008), we produce synthetic line width-size relations that shows a difference between the ion and neutral line widths, illustrating that two-fluid effects can have an observationally detectable role in modifying the MHD turbulence in the clouds.Comment: 18 pages, 4 figures, submitted to MNRA

Post-Outburst Observations of V1647 Ori: Detection of a Brief Warm, Molecular Outflow

We present new observations of the fundamental ro-vibrational CO spectrum of V1647 Ori, the young star whose recent outburst illuminated McNeil's Nebula. Previous spectra, acquired during outburst in 2004 February and July, had shown the CO emission lines to be broad and centrally peaked-similar to the CO spectrum of a typical classical T Tauri star. In this paper, we present CO spectra acquired shortly after the luminosity of the source returned to its pre-outburst level (2006 February) and roughly one year later (2006 December and 2007 February). The spectrum taken in 2006 February revealed blue-shifted CO absorption lines superimposed on the previously observed CO emission lines. The projected velocity, column density, and temperature of this outflowing gas was 30 km/s, 3^{+2}_{-1}E18 cm^{-2$, and 700^{+300}_{-100} K, respectively. The absorption lines were not observed in the 2006 December and 2007 February data, and so their strengths must have decreased in the interim by a factor of 9 or more. We discuss three mechanisms that could give rise to this unusual outflow.Comment: 14 pages, 2 figures, accepted for publication in ApJ

Operando deconvolution of photovoltaic and electrocatalytic performance in ALD TiO2 protected water splitting photocathodes

The dual-working-electrode technique enables the deconvolution of the intrinsic properties of the buried p–n junction and the electrocatalyst on the surface for water splitting photocathodes

Calculation of the Energy Band Diagram of a Photoelectrochemical Water Splitting Cell

A physical model is presented for the semiconductor electrode of a photoelectrochemical cell. The model accounts for the potential drop in the Helmholtz layer and thus enables description of both band edge pinning and unpinning. The model is based on the continuity equations for charge carriers and direct charge transfer from the energy bands to the electrolyte. A quantitative calculation of the position of the energy bands and the variation of the quasi-Fermi levels in the semiconductor with respect to the water reduction and oxidation potentials are presented. Calculated photocurrent–voltage curves are compared with established analytical models and experimental data. Our model calculations are suitable to enhance understanding and improve the properties of semiconductors for photoelectrochemical water splitting

Comparison of Statistical Tests Distinguishing Error Dynamics and Systematic Dynamics in Distributed Lag Models

The Oklahoma Agricultural Experiment Station periodically issues revisions to its publications. The most current edition is made available. For access to an earlier edition, if available for this title, please contact the Oklahoma State University Library Archives by email at [email protected] or by phone at 405-744-6311

Phase vortices from a Young's three-pinhole interferometer

An analysis is presented of the phase vortices generated in the far field, by an arbitrary arrangement of three monochromatic point sources of complex spherical waves. In contrast with the case of three interfering plane waves, in which an infinitely-extended vortex lattice is generated, the spherical sources generate a finite number of phase vortices. Analytical expressions for the vortex core locations are developed and shown to have a convenient representation in a discrete parameter space. Our analysis may be mapped onto the case of a coherently-illuminated Young's interferometer, in which the screen is punctured by three rather than two pinholes.Comment: 10 pages, 8 figures, REVTeX4, Submitted to Phys. Rev.

Gravitational Collapse of Filamentary Magnetized Molecular Clouds

We develop models for the self-similar collapse of magnetized isothermal cylinders. We find solutions for the case of a fluid with a constant toroidal flux-to-mass ratio (Gamma_phi=constant) and the case of a fluid with a constant gas to magnetic pressure ratio (beta=constant). In both cases, we find that a low magnetization results in density profiles that behave as rho ~ r^{-4} at large radii, and at high magnetization we find density profiles that behave as rho ~ r^{-2}. This density behaviour is the same as for hydrostatic filamentary structures, suggesting that density measurements alone cannot distinguish between hydrostatic and collapsing filaments--velocity measurements are required. Our solutions show that the self-similar radial velocity behaves as v_r ~ r during the collapse phase, and that unlike collapsing self-similar spheres, there is no subsequent accretion (i.e. expansion-wave) phase. We also examine the fragmentation properties of these cylinders, and find that in both cases, the presence of a toroidal field acts to strengthen the cylinder against fragmentation. Finally, the collapse time scales in our models are shorter than the fragmentation time scales. Thus, we anticipate that highly collapsed filaments can form before they are broken into pieces by gravitational fragmentation.Comment: 20 pages, 4 figures, accepted to Ap