Genetics of an Isolated Population of Plethodon hubrichti

Undergraduate Basi

Spin bath interactions effects on the geometric phase

We calculate the geometric phase of a spin-1/2 particle coupled to an external environment comprising N spin-1/2 particle in the framework of open quantum systems. We analyze the decoherence factor and the deviation of the geometric phase under a nonunitary evolution from the one gained under an unitary one. We show the dependence upon the system's and bath's parameter and analyze the range of validity of the perturbative approximation. Finally, we discuss the implications of our results.Comment: 8 pages, 5 figures. Version to appear in Phys. Lett.

Classification of Stellar Spectra with LLE

We investigate the use of dimensionality reduction techniques for the classification of stellar spectra selected from the SDSS. Using local linear embedding (LLE), a technique that preserves the local (and possibly non-linear) structure within high dimensional data sets, we show that the majority of stellar spectra can be represented as a one dimensional sequence within a three dimensional space. The position along this sequence is highly correlated with spectral temperature. Deviations from this "stellar locus" are indicative of spectra with strong emission lines (including misclassified galaxies) or broad absorption lines (e.g. Carbon stars). Based on this analysis, we propose a hierarchical classification scheme using LLE that progressively identifies and classifies stellar spectra in a manner that requires no feature extraction and that can reproduce the classic MK classifications to an accuracy of one type.Comment: 15 pages, 13 figures; accepted for publication in The Astronomical Journa

The origin of mid-infrared emission in massive young stellar objects: multi-baseline VLTI observations of W33A

The circumstellar structure on 100 AU scales of the massive young stellar object W33A is probed using the VLTI and the MIDI instrument. N-band visibilities on 4 baselines are presented which are inconsistent with a spherically symmetric geometry. The visibility spectra and SED are simultaneously compared to 2D axi-symmetric dust radiative transfer models with a geometry including a rotationally flattened envelope and outflow cavities. We assume an O7.5 ZAMS star as the central source, consistent with the observed bolometric luminosity. The observations are also compared to models with and without (dusty and gaseous) accretion disks. A satisfactory model is constructed which reproduces the visibility spectra for each (u,v) point. It fits the silicate absorption, the mid-IR slope, the far-infrared peak, and the (sub)mm of the SED. It produces a 350 micron morphology consistent with observations. The 10 micron emission on 100 AU scales is dominated by the irradiated walls of the cavity sculpted by the outflow. The visibilities rule out the presence of dust disks with total (gas and dust) masses more than 0.01 Msun. However, optically thick accretion disks, interior to the dust sublimation radius, are allowed to accrete at rates equalling the envelope's mass infall rate (up to 10^(-3) Msun/yr) without substantially affecting the visibilities due to the extinction by the extremely massive envelope of W33A.Comment: Accepted for publication in A&

Master of Science

thesisIn order to understand quantitatively the various parameters that control the IP response in rocks, a series of measurements have been made on artificially prepared "rock" samples. These samples are ' prepared from mixtures of quartz sand, ore mineral grains and a cementing agent. The controlled parameters are concentrations of ore mineral, grain size, grain shape, mineralogy, porosity and pore structure. A theoretical complex resistivity rock model based on layered spheres is derived. It accounts for the microscopic charge separation within the diffuse zones between the electrolyte and mineral grains and the macroscopic decay of that charge build up through out the rock. Using inversion techniques the data are compared to the rock model parameters of, background resistivity ( p 1 , mineral grain radius (a), Warburg impedance (A), the frequency dependence (c) of the Warburg impedance, the volume fraction (V) of the mineral, and the resistivity contrast between the electrolyte (pe) and the mineral (p3 ). Results indicate that at low concentrations some of the observed dependencies are in approximate agreement with the rock model. The frequency range at which the dispersive region of the complex resistivity occurs was observed to be largely a function of Pj, a and A, which represent macroscopic rock conditions. Due to the rather limited range observed for the Warburg impedance of different minerals in various electrolyte concentrations, the position of the dispersion is a stronger function of P1 and a. The magnitude of the phase response, a function of a microscopic charge separation in the diffuse zones, was observed to depend on V , p3 , and pe . The volume fraction (V) of the mineral is relative to the conductive elements within the rock. Such conductive elements include the mineral, the electrolyte and clay type minerals (i.e. minerals which have a capacity for cation exchange). The degree of charge separation (polarization) was observed to be a strong function of the resistivity contrast between the electrolyte and the mineral. The frequency dependence (c) or the asymptotic phase slope was observed to be a function of the range of mineral grain sizes. For a limited range of grain sizes the frequency dependence (c) was around 0.5 indicating a simple Warburg diffusion impedance. A larger range of grain sizes resulted in smaller phase slopes due to the summation of dispersions, one for each grain size. A similar theoretical development for layered ellipsoids is combined with mixing formulas of Fricke (1953) for dispersed triaxial ellipsoids, which are then extended to include the effect of particle shape and frequency dependent behavior (complex conductivity). For some cases of nonspherical sample conditions a simple spherical model could distinguish textural differences of synthetic samples constructed to test the ellipsoidal model. With an appropriate regrouping of parameters the above model can be expressed in terms of a simple Cole-Cole model for the relaxation spectrum and thus can be related to the results of in situ field measurements. The inversion of core sample and in situ field IP spectra to the spherical model gave parameter results and trends which were approximately explained in some of the actual observations of rock and field site conditions. Possible applications of the model to in situ field IP measurements over disseminated and veined deposits include indication of . 1. electrolyte resistivity, porosity and/or alteration mineral (e.g. "clay") content variations. 2 . a conductive mineral volume fraction relative to the pore volume and the "clay" content. 3. a distinction between a random distribution of mineral shapes (e.g. veinlets) or a preferred orientaion. 4. a relative difference between dominant length scales (e.g. grain sizes) and/or dominant mineral Warburg impedance values between two different in situ IP measurements. 5. and a possible range of mineral grain dimensions in a deposit

Radiation Transfer of Models of Massive Star Formation. I. Dependence on Basic Core Properties

Radiative transfer calculations of massive star formation are presented. These are based on the Turbulent Core Model of McKee & Tan and self-consistently included a hydrostatic core, an inside-out expansion wave, a zone of free-falling rotating collapse, wide-angle dust-free outflow cavities, an active accretion disk, and a massive protostar. For the first time for such models, an optically thick inner gas disk extends inside the dust destruction front. This is important to conserve the accretion energy naturally and for its shielding effect on the outer region of the disk and envelope. The simulation of radiation transfer is performed with the Monte Carlo code of Whitney, yielding spectral energy distributions (SEDs) for the model series, from the simplest spherical model to the fiducial one, with the above components each added step-by-step. Images are also presented in different wavebands of various telescope cameras, including Spitzer IRAC and MIPS, SOFIA FORCAST and Herschel PACS and SPIRE. The existence of the optically thick inner disk produces higher optical wavelength fluxes but reduces near- and mid-IR emission. The presence of outflow cavities, the inclination angle to the line of sight, and the thickness of the disk all affect the SEDs and images significantly. For the high mass surface density cores considered here, the mid-IR emission can be dominated by the outflow cavity walls, as has been suggested by De Buizer. The effect of varying the pressure of the environment bounding the surface of the massive core is also studied. With lower surface pressures, the core is larger, has lower extinction and accretion rates, and the observed mid-IR flux from the disk can then be relatively high even though the accretion luminosity is lower. In this case the silicate absorption feature becomes prominent, in contrast to higher density cores forming under higher pressures.Comment: 19 pages, 14 figures, 2 tables, accepted for publication in Ap

Curriculum transformation to address the Sustainable Development Goals: A holistic approach for embedding gender in higher education

[EN] To better prepare a new generation of practitioners and thought leaders to meet the complex challenges highlighted in the sustainable development goals (SDGs), innovation is needed in the design and delivery of degree programmes. Gender inclusion and diversity are increasingly recognised as key tenets of Education for Sustainable Development. Energy access education in Africa provides an excellent context in which to explore ways of delivering gender inclusive Masters programmes and the curriculum transformations needed to address the dual challenges of SDG7 (energy access) and SDG 5 (gender equality). This paper explores the evolving context of gender mainstreaming in energy access education at Institutions of Higher Learning (IHLs) in Africa, drawing on a desktop study and interviews with 8 African Universities in the Transforming Energy Access Learning Partnership (TEA-LP). The paper calls for the adoption of a more holistic approach to mainstreaming gender in energy access education at IHLs, encompassing curriculum content, teaching methods, learning environments and the broader institutional enabling environment.This research was funded by the Foreign Commonwealth and Development Office Transforming Energy Access Programme, IATI Identifier: GB-1-204867. This paper benefited from the advice and support of Guy Cunliffe and Leslie Ashburner from the TEALP. The authors are grateful for their feedback.Pailman, W.; De Groot, J. (2021). Curriculum transformation to address the Sustainable Development Goals: A holistic approach for embedding gender in higher education. En 7th International Conference on Higher Education Advances (HEAd'21). Editorial Universitat Politècnica de València. 119-127. https://doi.org/10.4995/HEAd21.2021.12977OCS11912

Spitzer Observations of the HII Region NGC 2467: An Analysis of Triggered Star Formation

We present new Spitzer Space Telescope observations of the region NGC 2467, and use these observations to determine how the environment of an HII region affects the process of star formation. Our observations comprise IRAC (3.6, 4.5, 5.8, and 8.0 um) and MIPS (24 um) maps of the region, covering approximately 400 square arcminutes. The images show a region of ionized gas pushing out into the surrounding molecular cloud, powered by an O6V star and two clusters of massive stars in the region. We have identified as candidate Young Stellar Objects (YSOs) 45 sources in NGC 2467 with infrared excesses in at least two mid-infrared colors. We have constructed color-color diagrams of these sources and have quantified their spatial distribution within the region. We find that the YSOs are not randomly distributed in NGC 2467; rather, over 75% of the sources are distributed at the edge of the HII region, along ionization fronts driven by the nearby massive stars. The high fraction of YSOs in NGC 2467 that are found in proximity to gas that has been compressed by ionization fronts supports the hypothesis that a significant fraction of the star formation in NGC 2467 is triggered by the massive stars and the expansion of the HII region. At the current rate of star formation, we estimate at least 25-50% of the total population of YSOs formed by this process.Comment: Accepted to the Astrophysical Journal, set to appear in Volume 701; 18 pages, 13 figures, 4 tables. This version reflects a few major changes made in the accepted version, including new figure

An assembly oriented design framework for product structure engineering and assembly sequence planning

The paper describes a novel framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product life cycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context knowledge to support life-oriented product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a catalytic-converter and diesel particulate filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology