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Dissertations / Theses on the topic 'Astronomy, Astrophysics, Physical sciences'
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1
Wang, Xiqiao. "Accurate Hyperfine Coupling Calculations of Radiation Induced DNA Constituent Radicals Using Density Functional Theory." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/honors/59.
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Previous density functional theory (DFT) calculations of hyperfine coupling constants (HFCC) on single nucleic acid base radicals agree well with the EPR/ENDOR experiments’ values on radiation induced nucleic acid constituents radicals, except for four problem cases,1 namely the N1-deprotonated cytosine cation radical, the native guanine cation radical, the N3-deprotonated 5’-dCMP cation radical and the N7-H, O6-H protonated 5’-GMP anion. The main effort of the present work is to address these four discrepancies by using the highly parameterized density functional M05/6-2X and by including the crystalline environment’s H-bonding effects in the calculations. The geometries of the four model radicals are optimized within their single crystal environment using ONIOM technique. Then the spin density distributions and HFCCs of the radicals are examined within various scales of cluster models. The results obtained by including H-bonding environment are in strong agreement with the experimental values. The calculations show advantages of using the M05/62X functional rather than the B3LYP functional in obtaining more satisfactory HFCC results. However, the delocalization errors are encountered with both M05/6-2X and B3LYP functionals. Further development in eliminating delocalization errors in practical DFT approximations is suggested.
2
Miller, Olivia. "Reactive Intermediates in Hypoxia-Selective DNA Damage." Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/honors/73.
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A group of prospective drugs with the aromatic di-N-oxide (ANO) functionality as the common feature are currently undergoing testing for the ability to selectively target tumors surrounded by normal tissues. It has been long recognized that the mechanism of biological activity of these drugs involves DNA damage by free radical species generated through one-electron reduction, although the exact nature of the reactive intermediate responsible for DNA damage remains uncertain. It is believed, however, that one of the key factors defining, in particular, hypoxic selectivity of these drugs is the rate of N-O bond scission in the one-electron reduced intermediate. In this study we have made an attempt to verify whether the predictions made in the literature regarding the N-O bond dissociation rate in a related class of derivatives are applicable to the same process in ANO. For that purpose both theoretical (electronic structure calculations) and experimental (Electron Spin Resonance spectroscopy) have been employed. While our results are not conclusive, they have laid the groundwork for future studies.
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Musgraves, J. David. "Maskless Projection Lithography." Scholarship @ Claremont, 2003. http://scholarship.claremont.edu/pomona_theses/17.
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Photolithography is a key element of the modem integrated circuit process. It is photolithography, combined with metal deposition, that allows a three dimensional circuit to be built up on a two dimensional surface. Since it is such an important part of the semiconductor manufacturing industry, a massive base of research in this area already exists. The problem with this pre-existing research is that it is geared solely toward industrial purposes, as opposed to more academic research areas. The goal of my research is to move this industrial process into the academic setting of Pomom College.
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Semrén, Philip. "Dissipative Perturbations on LRS Class II Cosmologies Using the 1+1+2 Covariant Split of Spacetime." Thesis, Umeå universitet, Institutionen för fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-176037.
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By including dissipative fluxes in the description, this thesis extends previous results regarding first order perturbations on homogeneous and hypersurface orthogonal locally rotationally symmetric (LRS) class II cosmologies using the 1 + 1 + 2 covariant split of spacetime. Whereas previous works consider perturbations of perfect fluid type, perturbations pertaining to heat flux and fluid viscosity are here studied with the aim to ascertain their effect on the evolution of the fluid vorticity. The studied perturbations include scalar, vector, and tensor modes, and are harmonically decomposed to yield a system of ordinary differential equations. These equations, originating from the Bianchi identities, the Ricci identities for certain preferred vector fields, and the thermodynamic Eckart theory, then decouple into two independent systems. These separately closed systems, with four and eight remaining variables respectively, describe the evolution of perturbations pertaining to the Weyl tensor and the fluid shear, vorticity, heat flow, energy density, and number density. From the final system of equations it is seen that the inclusion of heat flux and fluid viscosity has the possibility to yield mechanisms for generating vorticity, even if this vorticity vanishes initially. This is in contrast to the case of barotropic perfect fluids, for which it can be shown that vorticity perturbations cannot be generated. The validity of the results presented here can be questioned, as the Eckart theory, which violates causality, is employed to describe the detailed thermodynamic properties of the fluid. However, on time scales much larger than the relaxation times of the fluid, it should still provide a decent description of the dissipative phenomena, provided that certain couplings between the dissipative fluxes can be neglected.
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Clayborne, Peneé Armaize. "Silicon Oxide Nanoparticles Reveal the Origin of Silicate Grains in Circumstellar Environments." VCU Scholars Compass, 2006. http://scholarscompass.vcu.edu/etd/1213.
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The processes leading to the widespread presence of crystalline silicates throughout the galaxy and the origin of silicon nanoparticles thought to be responsible for the observed extended red emission in diffuse galactic background are still far from being understood. One of the most abundant oxygen bearing species in molecular astronomical regions is SiO. It has been conjectured that silicate formation probably proceeds via the agglomeration of these molecular species; however there are no studies to reveal the microscopic mechanism. We have used a synergistic approach combining experiments in molecular beams and first principles theoretical calculation to demonstrate that the passage from SiO to Si02 proceeds via gradual oxygen enrichment of SinOm clusters and that the smallest cascade involves Si203, S304, Si405, Si506 as the intermediate products. We also demonstrate that as the SiO molecules cluster together, the chemistry drives the agglomerates towards configurations such that the central core are pure Sin clusters while the outer shell are SiO2 molecules. The gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital range from 0.84 to 3.84 eV and hence can contribute to the observed extended red emission and blue luminescence. The findings are of general interest in Astrophysics but are also critical to a fundamental understanding of the interstellar extinction.
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Frank, Ian W. "Shaping Graphene: An Alternative Approach." Scholarship @ Claremont, 2008. http://scholarship.claremont.edu/pomona_theses/23.
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With experimentation on graphene (an atomic layer of graphite) becoming more and more common it is imperative that we have the capability to shape the material beyond the random manner in which it is deposited by mechanical exfoliation. This capability would be invaluable not only for the interesting electronic and optical properties that can be obtained, but also potentially for characterizing the mechanical resonators that we have been able to fabricate here at Pomona College by suspending few-layer graphene sheets over trenches in SiO2. We propose novel methods for etching graphene that should allow us to shape the material when used in conjunction with our e-beam lithography capabilities.
7
Favia, Andrej. "An inventory of student recollections of their past misconceptions as a tool for improved classroom astronomy instruction." Thesis, The University of Maine, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3581942.
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Milewski, Thomas. "Analysis of planetary boundary layer : wind and thermodynamic structures over Great Bear Lake during varying synoptic-scale regimes." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99355.
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Surface observations, lake evaporation data and upper-air soundings were collected in a special data-collection effort during the months of August and September of 2004 and 2005 on an island in the middle of Great Bear Lake, Northwest Territories. For this period of the year, the late summer, when increasing variability in surface pressure starts occurring, the effect of different synoptic-scale regimes on the lake-atmosphere interface is investigated to understand the regional specificities, with comparisons to nearby stations and a high spatial and temporal resolution reanalysis model (North American Regional Reanalysis). The planetary boundary layer over the lake systematically shows typical surface and mixed layer structures but with varying depths depending on the mean lower tropospheric temperature. Inversions in the surface layer, linked with warm regimes, support deep mixed layers. Within the surface layer, during warm regimes, a superadiabatic lapse rate can support (or not) a higher-stability sublayer on top of it, in which case the mixed layer happens to be much deeper. The first mechanism for lake evaporation includes the occasional passage of synoptic-scale storm systems with both warm and cold frontal features creating strong, short-lived latent heat interactions between the lake and the atmosphere, but relatively low total amounts of evaporation. The main mechanism for extensive evaporation is a cold anticyclone allowing for significant daytime insolation. A lake-breeze circulation can then develop and provide strong-enough mesoscale winds for diurnal upward latent heat exchanges, with wind channelling into Keith Arm of the lake for strong lake-breeze onshore winds.
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Del, Campo Lua. "The Biomechanics of Ballistochory in Impatiens Pallida." Scholarship @ Claremont, 2008. http://scholarship.claremont.edu/pomona_theses/26.
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This research is an analysis of the explosive seed dispersal of Impatiens pallida fruit. Data was taken using high-speed video and analyzed using LoggerPro video analysis software. From the videos we discerned a qualitative model for dehiscence, a description of how the process unfolds, and from our data we deduced quantitative values for the velocity, momentum, and energy of the system. We were also able to glean a lower bound of Young’s modulus E of the fruit tissue. These results and the tools of analysis that generate them are the foundation for the development of a theoretical model of the plants motion. Our results also provide insights into Impatiens pallida’s evolutionary history by explaining its seed dispersal mechanism. A secondary benefit of this research is providing ecologist’s with new tools to analyze ultra-rapid movements in plants and fungi. These tools of analysis will assist in defining a plant’s or fungi’s evolutionary context and the ecological significance rapid motion plays.
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Gabici, Stefano. "Gamma ray astronomy and the origin of galactic cosmic rays." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2011. http://tel.archives-ouvertes.fr/tel-00719791.
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Diffusive shock acceleration operating at expanding supernova remnant shells is by far the most popular model for the origin of galactic cosmic rays. Despite the general consensus received by the model, an unambiguous and conclusive proof of the supernova remnant hypothesis is still missing. In this context, the recent developments in gamma ray astronomy provide us with precious insights into the problem of the origin of galactic cosmic rays, since production of gamma rays is expected both during the acceleration of cosmic rays at supernova remnant shocks and during their subsequent propagation in the interstellar medium. In particular, the recent detection of a number of supernova remnants at TeV energies nicely fits with the model, but it still does not constitute a conclusive proof of it, mainly due to the difficulty of disentangling the hadronic and leptonic contributions to the observed gamma ray emission. The main goal of my research is to search for an unambiguous and conclusive observational test for proving (or disproving) the idea that supernova remnants are the sources of galactic cosmic rays with energies up to (at least) the cosmic ray knee. Our present comprehension of the mechanisms of particle acceleration at shocks and of the propagation of cosmic rays in turbulent magnetic fields encourages beliefs that such a conclusive test might come from future observations of supernova remnants and of the Galaxy in the almost unexplored domain of multi-TeV gamma rays.
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Mount, Christopher P. "Spatial, temporal, and inter-annual variability of the Martian northern seasonal polar cap." Thesis, Northern Arizona University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1537795.
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<p>Earth and Mars have nearly the same axial tilt, so seasons on these two bodies progress in a similar manner. During fall and winter on Mars, the primarily CO<sub>2</sub> atmosphere (~95% by volume) condenses out onto the poles as ice. Approximately 25% of the entire Martian atmosphere condenses, and then sublimes in the spring, making this cycle a dominant driver in the global climate. Because the water and dust cycles are coupled to this CO<sub>2</sub> cycle, we must examine seasonal CO<sub>2</sub> processes to understand the global (seasonal) distribution of H<sub>2</sub>O on Mars. The density of the ice may indicate whether it condensed in the atmosphere and precipitated as “snow” or condensed directly onto the surface as “slab”. Variations in density may be controlled by geographic location and surface morphology. The distribution and variations in densities of seasonal deposits on the Martian poles gives us insight to the planet’s volatile inventories. Here we analyze density variations over time on Mars’ Northern Polar Seasonal Cap (NPSC) using observational data and energy balance techniques. </p><p> We calculate the bulk density of surface CO<sub>2</sub> ice by dividing the column mass abundance (the mass of CO<sub>2</sub> per unit area) by the depth of the ice cap at a given location. We use seasonal rock shadow measurements from High Resolution Imaging Science Experiment (HiRISE) images to estimate ice depth. The length of a rock’s shadow is related to its height through the solar incidence angle and the slope of the ground. </p><p> From differences in the height of a rock measured in icy vs. ice-free images, we estimate the depth of surface ice at the time of the icy observation. Averaging over many rocks in a region yields the ice depth for that region. This technique yields minimums for ice depth and therefore maximums for density. </p><p> Thermal properties of rocks may play an important role in observed ice depths. Crowns of ice may form on the tops of rocks with insufficient heat capacity to inhibit ice condensation, and may cause an artificial increase in shadow length. This increases the apparent height of a rock and thus decreases the apparent surface ice depth. Additionally, moats may form around rocks with sufficient heat capacity to sublime ice as it is deposited. Moating will also artificially increase the shadow lengths (decreasing apparent surface ice depth). We correct for these effects in our depth-estimation technique. </p><p> We balance incoming solar flux with outgoing thermal radiation from Thermal Emission Spectrometer (TES) observations to calculate the column mass abundance. TES thermal bolometer atmospheric albedo and temperature observations are a good proxy to the surface bond albedo and effective surface temperature. These parameters are needed to balance the incoming and outgoing flux. </p><p> Mars’ atmosphere is tenuous so we assume homogeneous radiance from the surface to the top of the atmosphere, no lateral diffusion of heat, and that any excess heat goes into subliming surface ice in our flux balance. Using a Monte Carlo model, we integrate the net flux until reaching the time where Cap Recession Observations indicate CO<sub>2</sub> has Ultimately Sublimed (the CROCUS date) to obtain the column mass abundance. </p><p> We study seasonal ice at three distinct geomorphic units: plains, dune fields, and craters. Two plains regions, four dunes regions, and two crater regions are analyzed over springtime sublimation. Data for these regions spanned three Mars Years. </p><p> Our results indicate that the evolution of seasonally deposited CO<sub> 2</sub> ice on the Northern Polar Cap of Mars is highly dependent on complex relationships between various processes. The grain size, dust contamination, water doping, and density vary dramatically over time. The initially deposited material varies according to local geomorphic features and topography, as well as latitude and longitude. The inter-annual variability of ice may play a role in its evolution over sublimation, but likely plays a smaller role than anticipated. Low normalized initial and time-averaged densities suggest that NPSC deposits are initially low and remain relatively low throughout spring. These densities are very similar to estimates made by previous studies. Thus, we conclude that the NPSC is indeed pervaded by low density deposits. These deposits densify over time, but rarely reach typical characteristics for pure slab ice. </p>
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Gillette, Sean. "The Effects of Seductive Details in an Inflatable Planetarium." Thesis, Walden University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3595482.
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<p> Astronomy is becoming a forgotten science, which is evident by its relatively low enrollment figures compared to biology, chemistry, and physics. A portable inflatable planetarium brings relevance back to astronomy and offers support to students and educators by simulating realistic astronomical environments. This study sought to determine if learning is improved in an inflatable planetarium by adhering to the design principles of the cognitive theory of multimedia learning (CTML), specifically the coherence principle, in an authentic classroom. Two groups of 5<sup>th</sup> grade students of similar ability were purposefully assigned using a 1-teacher-to-many-students format with mean lesson lengths of 34 minutes. The experimental group was differentiated with <i>seductive details</i>, defined as interesting but irrelevant facts that can distract learning. The control group (<i> n</i> = 28), with seductive details excluded, outperformed the experimental group (<i>n</i> = 28), validating the coherence principle and producing a Cohen's effect size of medium practical significance (<i>d</i> = 0.4). These findings suggest that CTML, when applied to planetarium instruction, does increase student learning and that seductive details do have a negative effect on learning. An adult training project was created to instruct educators on the benefits of CTML in astronomy education. This study leads to positive social change by highlighting astronomy education while providing educators with design principles of CTML in authentic settings to maximize learning, aid in the creation of digital media (astronomical simulations/instructional lessons for planetariums) and provide valuable training for owners of inflatable planetariums with the eventual goal of increasing student enrollment of astronomy courses at the local level.</p>
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Lapham, Ryen C. "UV, Optical, and Infrared Imaging of the Interacting Galaxy Arp 107 and its Star Forming Regions." Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/honors/19.
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In this study we present GALEX UV, Sloan Digital Sky Survey, and Spitzer infrared imaging, along with an optical Hα map of the interacting galaxy pair Arp 107. IRAF photometry was used to analyze 29 star forming regions identified in previous work done with Spitzer colors. In this paper further analysis of the clumps of newly formed stars was done by creating Spectral Energy Distribution plots to sort the clumps as quiescent or starbursts. Color - color plots were used to estimate the ages and extinctions of the clumps by comparing magnitudes to stellar population synthesis models. Results seem to agree with previous models, and indicate a sequence of increasing age around the galaxy arm.
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Nyholm, Anders. "Astronomi i läroböckerna för gymnasiekursen Fysik 2 : Granskning av astronomiska illustrationer i fyra fysikläroböcker utgivna 2012-2019." Thesis, Stockholms universitet, Institutionen för matematikämnets och naturvetenskapsämnenas didaktik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-194829.
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Astronomi fascinerar många och har spelat en avgörande roll i fysikens utveckling. I det svenska gymnasiets läroplan Gy2011 ingår astronomi i kursen Fysik 2. Tidigare intervjustudier har visat att lärare som undervisar i Fysik 2 ofta ger astronomidelen låg vikt och att den ofta knyts starkt till lärobokens innehåll. Det senare gör det intressant att granska hur de aktuella läroböckerna i Fysik 2 behandlar den astronomiska delen av denna kurs. I detta arbete granskas illustrationer ur astronomikapitlen i fyra läroböcker i Fysik 2 utgivna 2012-2019. För att avgöra vilka möjligheter illustrationerna erbjuder att urskilja detaljer som är relevanta för ämnet används begreppen affordans, disciplinär urskiljning och variation. Med dessa begrepp som stöd granskas ett urval av illustrationer (ett fotografi av den variabla stjärnan RS Puppis, bilder av Krabbnebulosan i olika våglängdsområden respektive tre versioner av hubblediagrammet). En del illustrationer visar sig ha lågt pedagogiskt värde, vilket beror på att de inte valts ändamålsenligt eller på att de kopplas svagt till omgivande text. Storleken hos synfältet i de sammanlagt 42 astronomiska bilder (t.ex. fotografier) som finns i kapitlen granskas också. Synfältets bredd i bilderna sträcker sig från 0,000002' till 120 grader (med medianvärdet 12') men synfältens storlek kommenteras inte i kapiteltexterna och variationen används inte för något pedagogiskt syfte.
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Giebels, Berrie. "A contribution to gamma-ray astronomy of GeV-TeV Active Galaxies with Fermi and H.E.S.S." Habilitation à diriger des recherches, Ecole Polytechnique X, 2011. http://tel.archives-ouvertes.fr/tel-00672596.
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L'astronomie des rayons g de haute (E > 100MeV, HE) et de très haute énergie (E 100GeV, VHE) ont effectué des progrès considérables en moins d'une décennie. Le nombre de sources émettrices dans ce régime d'énergie a augmenté de plus d'un ordre de grandeur, de nouvelles classes d'émetteurs ont été découvertes et des nouvelles sous-classes ont été établies basées sur l'émission gamma, et les sources connues sont à présent résolues à des échelles spatiales ou temporelles sans précédent révélant de nouvelles propriétés. Les noyaux actifs de galaxie (AGN) sont l'une des classes d'émetteurs les plus énergétiques, dont le pic de puissance émis dans le spectre électromagnétique peut dans certains cas dépasser la capacité de mesure des instruments actuels, et dont l'investigation requiert la maîtrise simultanée du ciel g HE et VHE qu'apportent les expériences Cerenkov au sol (atmospheric Cerenkov telescope, ou ACT) et le satellite Fermi.
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Stecklein, Gordon. "Bridging the Gender Gap in Quantum Physics." Scholarship @ Claremont, 2008. http://scholarship.claremont.edu/pomona_theses/24.
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Why is it important to study the gender gap in physics? Despite entering the workforce in increasing numbers over the last fifty years, women remain severely underrepresented in science and technology-related careers, particularly in positions of authority. Simultaneously, numerous studies verify that women have the ability to perform as well as – or better than – males in physics, and, when presented in certain lights, as many women as men show an interest in physics. Changes must be made in order to strive for equality and, given the changing demographic of the workforce, increase our country’s diminishing scientific prowess.
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Jones, Mark. "Determining the Rotational and Orbital Velocities of Objects in the Solar System." Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/honors/585.
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Astronomers have been observing the night sky for many centuries to establish a better understanding for our universe and solar system. As part of their observations, astronomers characterize celestial bodies by fundamental properties such as mass, motion, and composition in order to provide further insight about the objects in question. As technology and science have evolved, the methods for measuring these properties have become more precise and accurate. One such methodology is known as spectroscopy, and it is a significant tool for observational astronomy. In this paper, we shall describe how we used astronomical spectroscopy to determine orbital and rotational velocities for various objects in our solar system. This method was implemented specifically using the facilities of the Harry D. Powell Observatory on the campus of East Tennessee State University.
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Volk, Kathryn Margaret. "Dynamical studies of the Kuiper belt and the Centaurs." Thesis, The University of Arizona, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3560868.
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<p> The Kuiper belt is a population of small bodies located outside Neptune's orbit. The observed Kuiper belt objects (KBOs) can be divided into several subclasses based on their dynamical structure. I construct models for these subclasses and use numerical integrations to investigate their long-term evolution. I use these models to quantify the connection between the Kuiper belt and the Centaurs (objects whose orbits cross the orbits of the giant planets) and the short-period comets in the inner solar system. I discuss how these connections could be used to determine the physical properties of KBOs and what future observations could conclusively link the comets and Centaurs to specific Kuiper belt subclasses. </p><p> The Kuiper belt's structure is determined by a combination of long-term evolution and its formation history. The large eccentricities and inclinations of some KBOs and the prevalence of KBOs in mean motion resonances with Neptune are evidence that much of the Kuiper belt's structure originated during the solar system's epoch of giant planet migration; planet migration can sculpt the Kuiper belt's scattered disk, capture objects into mean motion resonances, and dynamically excite KBOs. Different models for planet migration predict different formation locations for the subclasses of the Kuiper belt, which might result in different size distributions and compositions between the subclasses; the high-inclination portion of the classical Kuiper belt is hypothesized to have formed closer to the Sun than the low-inclination classical Kuiper belt. I use my model of the classical Kuiper belt to show that these two populations remain largely dynamically separate over long timescales, so primordial physical differences could be maintained until the present day. </p><p> The current Kuiper belt is much less massive than the total mass required to form its largest members. It must have undergone a mass depletion event, which is likely related to planet migration. The Haumea collisional family dates from the end of this process. I apply long-term evolution to family formation models and determine how they can be observationally tested. Understanding the Haumea family's formation could shed light on the nature of the mass depletion event.</p>
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Ritchie, Douglas Allen. "Factors That Affect the Global Positioning System and Global Navigation Satellite System in an Urban and Forested Environment." Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etd/2089.
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The purpose of this study was to evaluate the accuracy in real time measurements acquired from GPS and GLONASS satellite observations using RTK techniques in an urban and forested environment. To determine this accuracy, 2 data sets of 3-dimensional coordinates were created and compared at 14 stations situated at East Tennessee State University. One data set included coordinates determined by conventional land survey methods; the second was solved by RTK GPS/GLONASS. Once the magnitude of any deviation in the coordinate positions was determined, the contributions to the accuracies from cycle slips, multipath, satellite availability, PDOP, and fixed or float solutions were evaluated. Three points in the urban environment varied from the conventional data set. Multipath was assumed to be the major bias in these points. Seven points in the forested environment varied from the conventional data set. The use of float solutions and high PDOP may have caused this bias.
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Cox, Isaiah, and Beverly J. Smith. "Multi-Wavelength Statistics of Clumpy Galaxies." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/asrf/2018/schedule/100.
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We calculated the fraction of ‘clumpy’ galaxies (fclumpy) for three samples of nearby galaxies. These samples include interacting galaxies with strong tidal features, collisional ring galaxies, and normal spiral galaxies. We define a ‘clumpy’ galaxy as a galaxy that has luminous star-forming regions contributing more than 8% of the total flux for the galaxy. We calculate fclumpy for 16 different wavelengths. We find that fclumpy is highest in the ultraviolet, Hα, and 24μm, while fclumpy is the lowest in optical and near-infrared wavelengths. We also see a significant increase in fclumpy for the interacting samples compared to the normal spirals.
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Fraser, Eric M. "Deep-UV Light Emitting Diodes: An Experimental Investigation of Characterization and Optimization Techniques." Scholarship @ Claremont, 2005. http://scholarship.claremont.edu/pomona_theses/11.
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Light emitting diodes (LEDs) and laser diodes (LDs) have many advantages over conventional light sources. Current commercial LEDs span the spectrum from IR to near- UV. There are a variety of applications for devices that extend into the deep-UV, including biological agent detection and optical storage. The nitride material system is a set of semiconducting compounds that have wavelengths that span a broad range, from yellow to deep-UV. AlGaN has a direct bandgap that extends into the deep-UV range; we will try to grow device-quality material, deposited epitaxially using metalorganic chemical vapor deposition on sapphire substrates.
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Allison, J. R. "Observations of the Sunyaev-Zel'dovich effect using the Cosmic Background Imager 2." Thesis, University of Oxford, 2010. http://ora.ox.ac.uk/objects/uuid:c6b10ecf-3b50-4c2a-9ee1-0fe8dd93e580.
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This thesis describes the analysis of pointed thermal Sunyaev-Zel'dovich (SZ) effect data from observations using the Cosmic Background Imager 2 (CBI2). CBI2 is an upgrade to the original Cosmic Background Imager, with antennas that have twice the effective collecting area, and hence provide greater sensitivity on longer baselines. Observations of the thermal SZ effect constrain the line-of-sight integrated gas pressure within clusters of galaxies and, when combined with X-ray data, provide an excellent tool for deriving the physical properties of these large structures. The CBI2 SZ data combine relatively low-resolution with a large field-of-view, and can therefore be used to constrain the gas properties of medium-redshift clusters out to the virial radius. By jointly fitting a suitable analytical model to SZ data and X-ray surface brightness data, it is possible to obtain constraints on the temperature and total mass of the cluster. For the analysis work presented in this thesis I choose to parametrise the gas based upon the known behaviour of the entropy, and the total mass by the Navarro, Frenk and White (NFW) prescription. This model is tested against Hydrodynamic/N-body simulations and is found to reproduce the radial behaviour of key cluster properties. The CBI2 observations presented in this work focus on the REFLEX-DXL clusters, an X-ray luminous sub-sample of the REFLEX survey at z ~ 0.3, which have previously published X-ray surface brightness data. The Bullet Cluster, a significant merger system, is a member of this sample and is presented here as a case study for use of the entropy-based model. The derived total mass and gas mass fraction of this cluster are found to be consistent with results from previous X-ray observations. The derived properties from the REFLEX-DXL sample are used to construct a preliminary set of SZ scaling relations out to the virial radius, and are found to be consistent with the self-similar model for massive clusters.
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Foresman, Bryant R. "Acoustical measurement of the human vocal tract: quantifying speech & throat-singing." Pomona College, 2008. http://ccdl.libraries.claremont.edu/u?/stc,43.
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The field of biological acoustics has witnessed a steady increase in the research into overtone singing, or “throat-singing,” in which a singer utilizes resonance throughout the vocal tract to sing melodies with the overtones created by a vocal drone. Recent research has explored both how a singer vocalizes in order to obtain rich harmonics from a vocal drone, as well as how further manipulations of the vocal apparatus function to filter and amplify selected harmonics. In the field of phonetics, vowel production is quantified by measuring the frequencies of vocal tract resonances, or formants, which a speaker manipulates to voice a particular vowel. Thus, an investigation of throat singing is closely linked to human speech production. Formants are usually detected in vowel spectra obtained using Fast Fourier Transform algorithms (FFTs). An alternative method that provides much higher frequency resolution is external excitation of the vocal tract and measurement of the pressure response signal at the mouth’s opening, which can be used to calculate the acoustic impedance spectrum. We demonstrate the use of such an “acoustic impedance meter” to measure the formant frequencies of common vowels as well as the oscillatory modes of simple resonant pipe systems. The impedance meter accurately measures fundamental pipe modes and a variety of formant frequencies with an uncertainty of 1 Hz. Finally, we assess how the impedance meter may be used to measure the unique resonances achieved by qualified throat singers.
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Rowe, Adrienne. "Age of the Gliese 569 Multiple System." Honors in the Major Thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1188.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.<br>Bachelors<br>Sciences<br>Physics
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Ahlvind, Julia. "Magnificent beasts of the Milky Way: Hunting down stars with unusual infrared properties using supervised machine learning." Thesis, Uppsala universitet, Observationell astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446965.
Full textAbstract:
The significant increase of astronomical data necessitates new strategies and developments to analyse a large amount of information, which no longer is efficient if done by hand. Supervised machine learning is an example of one such modern strategy. In this work, we apply the classification technique on Gaia+2MASS+WISE data to explore the usage of supervised machine learning on large astronomical archives. The idea is to create an algorithm that recognises entries with unusual infrared properties which could be interesting for follow-up observations. The programming is executed in MATLAB and the training of the algorithms in the classification learner application of MATLAB. Each catalogue; Gaia+2MASS+WISE contains ~109, 5×108 and 7×108 (The European Space Agency 2019, Skrutskie et al. 2006, R. M. Cutri IPAC/Caltech) entries respectively. The algorithms searches through a sample from these archives consisting of 765266 entries, corresponding to objects within a <500 pc range. The project resulted in a list of 57 entries with unusual infrared properties, out of which 8 targets showed none of the four common features that provide a natural physical explanation to the unconventional energy distribution. After more comprehensive studies of the aforementioned targets, we deem it necessary for further studies and observations on 2 out of the 8 targets (Nr.1 and Nr.8 in table 3) to establish their true nature. The results demonstrate the applicability of machine learning in astronomy as well as suggesting a sample of intriguing targets for further studies.<br>Inom astronomi samlas stora mängder data in kontinuerligt och dess tillväxt ökar snabbt för varje år. Detta medför att manuella analyser av datan blir mindre och mindre lönsama och kräver istället nya strategier och metoder där stora datamängder snabbare kan analyseras. Ett exempel på en sådan strategi är vägledd maskininlärning. I detta arbete utnyttjar vi en vägled maskininlärnings teknik kallad klassificering. Vi använder klassificerings tekniken på data från de tre stora astronomiska katalogerna Gaia+2MASS+WISE för att undersöka användningen av denna teknik på just stora astronomiska arkiv. Idén är att skapa en algorithm som identifierar objekt med okontroversiella infraröda egenskaper som kan vara intressanta för vidare observationer och analyser. Dessa ovanliga objekt är förväntade att ha en lägre emission i det optiska våglängdsområdet och en högre emission i det infraröda än vad vanligtvis är observerad för en stjärna. Programmeringen sker i MATLAB och träningsprocessen av algoritmerna i MATLABs applikation classification learner. Algoritmerna söker igenom en samling data bestående av 765266 objekt, från katalogerna Gaia+2MASS+WISE. Dessa kataloger innehåller totalt ~109, 5×108 och 7×108 (The European Space Agency 2019, Skrutskie et al. 2006, R. M. Cutri IPAC/Caltech) objekt vardera. Det begränsade dataset som algoritmerna söker igenom motsvarar objekt inom en radie av <500 pc. Många av de objekt som algoritmerna identifierade som ”ovanliga” tycks i själva verket vara nebulösa objekt. Den naturliga förklaringen för dess infraröda överskott är det omslutande stoft som ger upphov till värmestrålning i det infraröda. För att eliminera denna typ av objekt och fokusera sökningen på mer okonventionella objekt gjordes modifieringar av programmen. En av de huvudsakliga ändringarna var att introducera en tredje klass bestående av stjärnor inneslutna av stoft som vi kallar "YSO"-klassen. Ytterligare en ändring som medförde förbättrade resultat var att introducera koordninaterna i träningen samt vid den slutgiltiga klassificeringen och på så vis, identifiering av intressanta kandidater. Dessa justeringar resulterade i en minskad andelen nebulösa objekt i klassen av ”ovanliga” objekt som algoritmerna identifierade. Projektet resulterade i en lista av 57 objekt med ovanliga infraröda egenskaper. 8 av dessa objekt påvisade ingen av det fyra vanligt förekommande egenskaperna som kan ge en naturlig förklaring på dess överflöd av infraröd strålning. Dessa egenskaper är; nebulös omgivning eller påvisad stoft, variabilitet, Hα emission eller maser strålning. Efter vidare undersökning av de 8 tidigare nämnda objekt anser vi att 2 av dessa behöver vidare observationer och analys för att kunna fastslå dess sanna natur (Nr.1 och Nr.8 i tabell 3). Den infraröda strålningen är alltså inte enkelt förklarad för dessa 2 objekt. Resultaten av intressanta objekt samt övriga resultat från maskininlärningen, visar på att klassificeringstekniken inom maskininlärning är användbart på stora astronomiska datamängder.
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Knödlseder, Jürgen. "The origin of 26Al in the Galaxy." Phd thesis, Université Paul Sabatier - Toulouse III, 1997. http://tel.archives-ouvertes.fr/tel-00145359.
Full textAbstract:
The history of recent galactic nucleosynthesis activity can be studied by <br />measurements of the 1.809 MeV gamma-ray line arising from the decay of <br />radioactive 26Al.<br />The COMPTEL telescope aboard the Compton Gamma-Ray Observatory, launched on <br />April 5, 1991, permits for the first time an extensive investigation of the <br />1.8 MeV radiation throughout the entire sky.<br />The aim of this thesis is to infer the galactic distribution of 26Al from <br />these measurements and to identify the dominant sources of this <br />radioactive isotope.<br /><br />The first part of the thesis is dedicated to the reconstruction of <br />the 1.8 MeV intensity distribution from the measured data.<br />It is demonstrated that the use of conventional deconvolution <br />algorithms, like maximum likelihood or maximum entropy inversion, <br />leads to lumpy, noise-dominated intensity distributions.<br />Nevertheless, simulations can help to assess the uncertainties in the <br />reconstructed images, which permits the scientific exploitation of the <br />recovered skymaps.<br />Alternatively, a multiresolution approach is proposed, which largely <br />reduces the uncertainties in the reconstructed 1.8 MeV intensity <br />distribution.<br />In summary, 1.8 MeV emission is mainly concentrated towards the <br />galactic plane, which clearly demonstrates that the bulk of 26Al is of <br />galactic rather than local origin.<br />However, distinct emission features towards Cygnus, Carina, and the <br />Auriga-Camelopardalis-Perseus region are inconsistent with a smooth <br />galactic 1.8 MeV emission profile, pointing towards a massive star <br />origin of 26Al.<br /><br />The second part of the thesis consists of a multi-wavelength <br />comparison of COMPTEL 1.8 MeV data which aims in the <br />identification of the origin of galactic 26Al.<br />For the comparison, a rigorous Bayesian analysis is applied, which <br />is the only consistent framework that allows inference based on the <br />comparison.<br />It turned out that the 1.8 MeV distribution follows very closely <br />the distribution of free electrons in the Galaxy which is traced by <br />thermal bremsstrahlung, observable in the microwave domain.<br />The similarity of the 1.8 MeV intensity distribution to the<br />thermal bremsstrahlung distribution implies a direct proportionality <br />between the 26Al and the massive star column densities, which strongly <br />supports that massive stars are the origin of galactic 26Al.<br />In particular, ONeMg-novae and AGB stars can be excluded as dominant <br />26Al sources since their galactic distribution is not expected to <br />correlate with the distribution of free electrons.<br /><br />The correlation between 26Al and free electrons established, the <br />analysis of 1.8 MeV gamma-ray line emission can complement our knowledge <br />about star formation and the distribution of ionized gas throughout <br />the entire Galaxy. <br />While COMPTEL made the first step in providing the first all-sky map <br />in the light of the 1.809 MeV line, INTEGRAL, the next generation gamma-ray spectrometer, will allow a detailed study of current star formation <br />in the Galaxy.
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Koulakis, John. "The viscous catenary." Pomona College, 2006. http://ccdl.libraries.claremont.edu/u?/stc,3.
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Variational techniques are used to develop a theory for the time evolution of a thin strand of viscous fluid suspended from two points. The shape of the strand is approximated to be a parabola and energy conservation is used to derive a differential equation modeling the change in height over time. Data is collected with a high resolution camera and a strobe light to obtain the position and shape of the strand over multiple intervals of time. Three very different and unexpected types of behaviors are observed depending on the initial thickness and shape of the filament. The approximation fits well with one type of behavior but variations in the thickness of the strand, and consequently in the center of mass, need to be factored in to predict the others.
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McFarland, James. "Investigation of carbon nanotube growth using a nozzle CVD method." Pomona College, 2006. http://ccdl.libraries.claremont.edu/u?/stc,4.
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This work uses a modification of the chemical vapor deposition (CVD) technique to study the effects of source gas flow geometry (and the corresponding parameters) on carbon nanotube growth. Our approach is to flow the carbon-containing source gas through a nozzle, projecting the gas stream onto targeted regions of the substrate. This technique not only allows the potential for localized nanotube growth, but also offers an interesting opportunity to provide an experimental test of theoretical nanotube growth models.
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Murugan, Anand. "Fuzzy blackholes." Pomona College, 2007. http://ccdl.libraries.claremont.edu/u?/stc,18.
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The fuzzball model of a black hole is an attempt to resolve the many paradoxes and puzzles of black hole physics that have revealed themselves over the last century. These badly behaved solutions of general relativity have given physicists one of the few laboratories to test candidate quantum theories of gravity. Though little is known about exactly what lies beyond the event horizon, and what the ultimate fate of matter that falls in to a black hole is, we know a few intriguing and elegant semi-classical results that have kept physicists occupied. Among these are the known black hole entropy and the Hawking radiation process.
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Kim, Jihun. "Assembly of a large common mount astronomical interferometer." Thesis, The University of Arizona, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3559991.
Full textAbstract:
<p>A large multi-aperture telescope has the potential to reach the diffraction limit corresponding to its baseline. To do so, Adaptive Optics (AO) and beam combination are critical to good performance. Operation as an interferometer is a complicated mode for the telescope. The system now has much tighter tolerances and is difficult to align. The alignment process needs to be planned in multiple steps, and tolerance and sensitivity analysis needs to be performed for each step. Alignment tools can be prepared based on the resolution found in the sensitivity analysis in each step. </p><p> Random fluctuation is another critical factor that reduces system performance. If noise sources near the telescope are characterized and identified, image quality can be improved by post-image processing. </p><p> Measuring the outer scale of atmosphere is also helpful for understanding the system performance. The fringe tracking method in the Large Binocular Telescope Interferometer (LBTI) system provides optical path difference (OPD) variation, and the power spectral density of the OPD variation is used to estimate the size of the outer scale. However, this method is limited by the baseline of the LBTI by 5[special characters omitted] B, where B is the baseline, and by this equation the outer scale size which is able to be estimated should be more than 125 m. </p><p> AO simulation can provide an understanding of new AO system concepts and parameter variations before they are applied to the real system. In this dissertation study, we simulated an LBTI system with structural vibration of 10 Hz and 20 Hz and with various amplitudes. From the simulation, we learned that the slower bandwidth of piston-correcting systems allows stars as faint as ~13<sup>the</sup> magnitude to be observed. If there is significant vibration on the structure, the increased bandwidth will limit the phasing stars to 10~11<sup>th</sup> magnitudes. This demonstrates the limits of the LBTI system regarding structural vibration. </p><p> An alternative phasing sensor for the LBTI system, the pseudo phasing sensor, can be used for more than 1000 m of outer scale of atmosphere. If the direct phasing sensor embedded in the LBTI system cannot be used for a very faint star, the pseudo phasing sensor, which approximately estimates the phase difference by AO wavefront sensor, can be useful for atmospheric conditions with estimated outer scale of about 1000 m. </p><p> The analyses in this dissertation provide a partial guide for developing large-scale telescopes and astronomical instruments.</p>
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Nelson, Erica. "H I line profiles of galaxies: tilted ring models." Pomona College, 2008. http://ccdl.libraries.claremont.edu/u?/stc,46.
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Two-dimensional information on the kinematics and spatial distribution of gas in spiral galaxies is encoded in radio observations of their one-dimensional 21-cm neutral hydrogen (HI) line profiles. More than ten thousand HI profiles have been published and are publicly available. In order to explore the parameter space mapped out by the 21-cm neutral hydrogen line pro file, we have modified and run a FORTRAN-based computer simulation code. We have identified 7 control parameters that define the morphology of the modelled galaxy: they describe the neutral hydrogen gas distribution (density and spatial location of the gas), characteristics of its rotation curve, warps, asymmetries, and finally, the viewing angle. All except the last of these parameters tell us significant physical information about the galaxy but a determination of them is not immediately apparent from the two-dimensional 21-cm line profile. Hence, the goal of this exploration is to find meaningful correlations between the observed 21-cm line profile features and the underlying physical parameters.
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Petrillo, Kristen. "A study of interacanding and companion galaxies: implications for cosmology." Pomona College, 2008. http://ccdl.libraries.claremont.edu/u?/stc,47.
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This paper examined a few different types of interacting galaxies and the implications the data has on cosmological theories. An analysis of the Holmberg Effect, Holmberg (1969)’s observation that companion galaxies tend to be near the poles of edge-on galaxies rather than in the planes, was done by reexamining the spirals viewed by Holmberg. Only using radial velocity confirmed companions to test for this effect showed that if anything, the opposite of the Holmberg effect is true. However, due to small number statistics, more edge-on spirals and their companions would have to be viewed in order to determine if this is an actual physical effect of anisotropic companion distribution around primary galaxies. It is important to discover if there is a preferred distribution, because it could point to the distribution of dark matter around the primary galaxies, and have interesting impacts on large-scale universal structure and cosmology theory.
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Carns, Regina C. "Patterning polymer thin films: lithographically induced self assembly and spinodal dewetting." Pomona College, 2004. http://ccdl.libraries.claremont.edu/u?/stc,5.
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In an age in which the microchip is ubiquitous, the rewards for novel methods of microfabrification are great, and the vast possibilities of nanotechnology lie just a little ahead. Various methods of microlithography offer differing benefits, and even as older techniques such as optical lithography are being refined beyond what were once considered their upper limits of resolution, new techniques show great promise for going even further once they reach their technological maturity. Recent developments in optical lithography may allow it to break the 100-nm limit even without resorting to x-rays.
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Ignace, Richard. "Astro4U: An Introduction to the Science of the Cosmos." Digital Commons @ East Tennessee State University, 2017. https://www.amzn.com/1516506782/.
Full textAbstract:
The book Astro4U: An Introduction to the Science of the Cosmos excites students about the grandeur of astronomy and how the universe functions. Filled with vibrant figures and informative tables that support the written text, the book has a fresh, casual, student-friendly tone that dramatically increases interest in the material while also making it more accessible.The book provides a college-level description of science, with astronomy serving as the vehicle of delivery for displaying the scientific model. The content follows a traditional progression, beginning with a study of the sky, followed by discussions of ancient and medieval astronomy, modern scientific practices, and key physical principles. Chapters move through the Solar System, stars, then galaxies, and finally the cosmos as a whole. The book presents astronomy as the story of light and gravity, crucial threads that run through the text. Chapters include Ponder Sections—in-depth, quantitative passages dealing with particular applications of interest such as “space junk”, the solar energy budget, and light travel time. Appendices provide information about physical constants, astronomical symbols, and multiple choice problem sets.Because students often express concern about the math content in astronomy classes, the book begins with a chapter entitled “Astro Maths” that reviews all the mathematical skills and concepts needed to complete the course. This up-front investment increases student confidence, eliminates one of the primary blocks students face, and improves chances for student achievement and success.Astro4U is written for general education survey courses in astronomy that are geared toward non-science majors.<br>https://dc.etsu.edu/etsu_books/1188/thumbnail.jpg
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Paterno-Mahler, Rachel. "Determining the AGN fraction of galaxy groups." Pomona College, 2007. http://ccdl.libraries.claremont.edu/u?/stc,17.
Full textAbstract:
Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction of groups compares to that of clusters. In the following sections, the author describes the mechanics of X-ray astronomy, the group environment, and the characteristics of active galactic nuclei. The author briefly describes the possible mechanisms for AGN fueling.
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Long, Stacy. "RR LYRAE CALIBRATION USING SDSS, SINGLE-EPOCH SPECTROSCOPY." UKnowledge, 2018. https://uknowledge.uky.edu/physastron_etds/56.
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I use single-epoch, SDSS spectroscopy of RR Lyraes identified in the Catalina survey to separate the spectra into same-temperature groups. Then I draw temperature-phase diagrams of the groups. I find shocked stars, improperly phased stars, low amplitude stars, and a few that are more likely eclipsing binaries. The RR Lyraes are then given precise metallicities by measurements of the CaII K and H-β, H-γ, and H-δ lines. This leads to better distance measurements, which allow me to confirm a distinction between the inner and outer galactic halo.
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Ignace, Richard. "Astro4U: An Introduction to the Science of the Cosmos." Digital Commons @ East Tennessee State University, 2014. http://amzn.com/1634870697.
Full textAbstract:
Astro maths -- The sky -- Astronomy of the ancients -- Renaissance astronomy -- The astronomer's toolbox: physical principles -- Overview of the solar system -- The sun, our nearest star -- Earth, the home world -- The moon -- The terrestrial planets -- The gas giant planets -- The dwarf planets -- Major moons of the solar system -- Solar system debris -- Properties of the stars -- The formation of stars -- The lives of stars -- Stellar corpses -- The interstellar medium -- Living in a galaxy called the milky way -- Galaxies -- Active galaxies and quasars -- Cosmology -- Exoplanets -- The search for life.
The book Astro4U: An Introduction to the Science of the Cosmos excites students about the grandeur of astronomy and how the universe functions. Filled with vibrant figures and informative tables that support the written text, the book has a fresh, casual, student-friendly tone that dramatically increases interest in the material while also making it more accessible. The book provides a college-level description of science with astronomy serving as the vehicle of delivery for displaying the scientific model. The content follows a traditional progression of scale, beginning with a study of the sky, followed by discussions of ancient and medieval astronomy, modern scientific practices, and key physical principles. Chapters move through the Solar System, stars, then galaxies, and finally the cosmos as a whole. Additionally, the book presents astronomy as the story of light and gravity, crucial threads that permeate the text. Because students often express concern about the math content in astronomy classes, the book begins with a chapter entitled "Astro Maths" that reviews all the mathematical skills and concepts needed to complete the course. This up-front investment increases student confidence, eliminates one of the primary blocks students face, and improves chances for student achievement and success. Astro4U is written for general education survey courses in astronomy that are geared to non-science majors.<br>https://dc.etsu.edu/etsu_books/1016/thumbnail.jpg
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Fernandes, Joshua M. "Physical and chemical properties of Jupiter's north and south polar vortex revealed through mid-infrared imaging." Thesis, California State University, Long Beach, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10263309.
Full textAbstract:
<p> This thesis reports on the characterization of the thermal and chemical distribution of Jupiter’s polar regions. The quantities are derived from mid-infrared images covering all longitudes at unprecedented spatial resolution using the COMICS instrument at the Subaru Telescope on the nights of January 24 and 25, 2016. Because of Jupiter’s slight axial tilt of 3° and low angular resolution and incomplete longitudinal coverage of previous mid-infrared observations, the physical and chemical properties of Jupiter’s polar regions have been poorly characterized. In advance of the exploration of the structure of Jupiter’s polar regions by the Juno spacecraft, this study focuses on mapping the 3-dimensional structure of Jupiter’s polar regions, specifically to characterize the polar vortices and compact regions of auroral influence. Using mid-infrared images taken in the 7.8 μm - 24.2 μm range, the 3-dimensional temperature field, para-H2 fraction, aerosol opacity, and the constraint on the distribution of gaseous-NH3 are determined on a range from 400 mbar to 100 mbar. Retrievals of these atmospheric parameters were performed using NEMESIS, a radiative transfer forward model and retrieval code. Results indicate that there are vortices at both poles, each with very distinct boundaries approximately 70° latitude in the north and -75° latitude in the south. The boundaries can be defined by sharp thermal gradients extending at least from the upper troposphere (500 mbar of atmospheric pressure) and into the stratosphere (0.1 mbar of atmospheric pressure). These polar regions are characterized by lower temperatures and lower para-hydrogen concentration, compared with the regions immediately outside the vortex boundaries.</p>
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Galata, Salvatore. "A time dependent search for neutrino emission from microquasars with the ANTARES telescope." Phd thesis, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00782883.
Full textAbstract:
La Collaboration ANTARES exploite actuellement un détecteur sous-marin Cherenkov d édi é a l'astronomie neutrino de haute énergie. Le but principal de cette expérience est de d détecter les sources cosmiques de neutrinos, a n de r ev eler les sites de production des rayons cosmiques. Parmi les sources candidates gurent celles o u a lieu l'acc el eration de ces rayons cosmiques dans les jets relativistes, comme les noyaux actifs de galaxie, les sursauts gamma et les microquasars. Les microquasars sont des syst émes stellaires binaires form es par un objet compact accr étant la mati ere d'une étoile compagnon. Ce transfert de masse est responsable de l' emission de rayons X, tandis que les forces magn etiques du plasma d'accr étion peuvent causer la cr éation de jets relativistes qui sont observ es par des t télescopes radio grâce au rayonnement synchrotron non thermique émis par les particules charg ées acc el er ees dans ces jets. Dans certains syst emes, la corr élation entre les courbes de lumi ere des rayons X et les courbes radio indique une interaction forte entre accr etion et ejection. Certains microquasars emettent egalement des rayons gamma de haute et tr es haute energie (jusqu' a quelques dizaines de TeV). Dans ce travail de th ese, une recherche d' émission de neutrinos provenant de microquasars a ét é conduite avec une approche multi-messager (photon/neutrino). Les données des satellites RXTE/ASM et SWIFT/BAT, ainsi que du t elescope gamma FERMI/LAT ont et e etudi ées a n de s sélectionner les périodes dans lesquelles se produisent les jets relativistes. La restriction de l'analyse des neutrinos aux phases d' éjection permet de r réduire drastiquement le bruit de fond de neutrinos et de muons atmosph èriques et ainsi d'augmenter les chances de d écouverte d'une source cosmique de neutrinos. Les recherches ont et e effectué a partir des donn ées ANTARES obtenues entre 2007 et 2010. Une analyse statistique a et e faite en utilisant une m ethode \unbinned" bas ee sur le test du rapport de vraisemblance. Les coupures de s élection des év enements ont et e optimisés a partir de simulations Monte Carlo a n de maximiser les chances de ddécouverte. Comme aucun signal de neutrinos n'a et e observé en corrélation avec ces microquasars, des limites sup erieures sur les ux de neutrinos produits dans ces microquasars ont et e calcul ées et confront ées avec des modèles de production de neutrino dans ces objets.
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Bauer, James Monie. "A physical survey of Centaurs." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/854.
Full textAbstract:
There are forty four known small planetary bodies with orbits that are contained within the heliocentric distances of Jupiter and Neptune. It is thought that the origin of these bodies is the Kuiper Belt, the predicted reservoir of the current short period comet population. Yet, only two bodies, Chiron and C/NEAT (2001 T4), have been shown to possess a visible coma. We've undertaken an observational survey of these bodies to obtain detailed characterization of the physical properties of the Centaurs to search for evidence of activity, and to use the physical characteristics to make inferences about primordial conditions in the outer solar nebula and evolutionary processes among different dynamical regimes in the outer nebula. We present the results of optical observations of 24 Centaurs, which yield a 3-σ correlation of color with semimajor axis, with redder Centaurs being farther from the Sun. The survey also revealed the rotation light curve period for 2 Centaurs, and the phase-darkening slope parameters, G, for 5 Centaurs which range from -0.18 to 0.13, agreeing with the steepest of main belt asteroid phase curve responses. We show spectral evidence of a variegated surface for 1999 UG5 and find the second reddest Centaur object is the active Centaur C/NEAT (2001 T4). We also present spectral evidence of crystalline water ice and ammonia species on our comparison object, the Uranian satellite Miranda.
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Ferguson, R. Matthew. "Steps toward the creation of a carbon nanotube single electron transistor." Pomona College, 2003. http://ccdl.libraries.claremont.edu/u?/stc,0.
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This report details work toward the fabrication of a single-electron transistor created from a single-walled carbon nanotube (SWNT). Specifically discussed is a method for growing carbon nanotubes (CNTs) via carbon vapor deposition (CVD). The growth is catalyzed by a solution of 0.02g Fe(NO3)3·9H2O, 0.005g MoO2(acac)2, and 0.015g of alumina particles in 15mL methanol. SWNT diameter ranges from 0.6 to 3.0 nm. Also discussed is a method to control nanotube growth location by patterning samples with small islands of catalyst. A novel “maskless” photolithographic process is used to focus light from a lightweight commercial digital projector through a microscope. Catalyst islands created by this method are approximately 400 μm2 in area.
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Vervack, Ronald Joe 1966. "Titan's upper atmospheric structure derived from Voyager ultraviolet spectrometer observations." Diss., The University of Arizona, 1997. http://hdl.handle.net/10150/282430.
Full textAbstract:
The Voyager 1 Ultraviolet Spectrometer (UVS) observations are the only direct measurements we have of Titan's upper atmosphere. Previous analysis of the two UVS solar occultations yielded densities for N₂ CH₄ and C₂ as well as the thermospheric temperature. These results serve as the upper atmospheric boundary conditions in models of Titan's atmosphere; however, there are discrepancies between the observations and models, and the previous analysis itself is known to be internally inconsistent. We have undertaken a reanalysis of the UVS solar occultations to resolve these differences and to extract the maximum amount of information from the data. In so doing, we have developed a detailed model of the UVS detector and a new analysis method tailored to retrieving multiple species from an occultation of a finite-sized source such as the sun. Our analysis has yielded density profiles for nine species in Titan's upper atmosphere and a new measurement of the thermospheric temperature. We find higher N₂ densities and lower CH₄ and C₂ densities than those previously determined. We also find a thermospheric temperature of 150-155 K instead of 176-196 K as in the early analysis. Densities for C₂H₄, C₂H₆, C₄H₂, C₂N₂, HCN, and HC₃N are retrieved for the first time. Titan's atmosphere is one of the most interesting in the solar system. The composition and high degree of photochemical activity elicit comparisons to the early terrestrial atmosphere and considerations about the origins of life. Our results provide improved and expanded constraints for the atmospheric models and should provide scientists with a better view of Titan's upper atmosphere, which is important in planning for the upcoming Cassini mission.
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Wegryn, Eric. "The dusty atmosphere of Mars: A study of the properties of martian aerosol dust, using Imager for Mars Pathfinder and Hubble Space Telescope observations." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289700.
Full textAbstract:
The properties of aerosol dust on Mars may be deduced from photometric observations of its atmosphere. By comparing sky images taken by the Imager for Mars Pathfinder to numerical models, the size distribution and reflective properties of the dust particles can be determined. The format, quality, and reduction of the IMP images is described herein, as is the computational radiative transfer model used, with its various parameters. After discovering and compensating for an imprecision in the pointing of the camera, models were successfully fit to the IMP solar aureole datasets. Key results include determining the particle size (reff = 1.6 ± 0.15 μm); quadratic parameters G and Θmin describing the phase function for internally scattered light as functions of wavelength; and the imaginary refractive index n i (and single scattering albedo o) of the aerosols as a function of wavelength (presented in Table 4.1). Preliminary indications of temporal variation in ni turn out to be due to an unplanned change in the time of day of the measurements, coupled with a limitation in the algorithm for correcting the aforementioned pointing imprecision. Excluding unreliable datasets leads to a set of particle properties which shows no significant variation over the first two months of the Pathfinder mission. A multispectral sky patch from MPF Sol 22 gives greater wavelength resolution, as well as showing the sensitivity of the results to variations in key model parameters. In addition, images from the Hubble Space Telescope are used to refine the surface reflectance used in the model. The final result is a model for the aerosol dust which is consistent with the IMP solar aureole observations and the HST observations. Evidence for a minor component of water ice is also discussed. Dust reflectances derived for comparison with ground spectra show a feature in the near infrared which is not present in most MPF spectra of bright surface regolith. This is an indication that there are components visible in the bright soil which are not present in the airborne dust.
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de, Naurois Mathieu. "L'astronomie gamma de très haute énergie de H.E.S.S. à CTA. Ouverture d'une nouvelle fenêtre astronomique sur l'Univers non thermique." Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00687872.
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Les dix dernières années ont été marquées par l'arrivée à maturité de la technique d'imagerie Cherenkov atmosphérique, ce qui a permis, notamment grâce au réseau de télescopes HESS, l'ouverture d'une nouvelle fenêtre sur l'Univers non thermique. Ce mémoire d'habilitation retrace dix années de recherche en Astronomie Gamma de Très Haute énergie avec HESS puis CTA. Les aspects techniques tels que la conception de l'instrument, son calibrage, la reconstruction des événements et l'analyse de données sont présentées dans une première partie, tandis que la seconde brosse un panorama des grandes découvertes dans ce domaine.
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Déry, Francis. "Interannual and intraseasonal variability of the ice cover in the Gulf of Saint Lawrence, 1963-1990." Thesis, McGill University, 1992. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=56975.
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Using a dataset of weekly ice cover in the Gulf of St. Lawrence, the intraseasonal and interannual variabilities of the mean ice cover fraction were investigated over the Gulf and six of its subregions for the 1963-90 period. Climatological seasonal cycles were calculated by averaging the weekly ice cover fraction means over the sampling period. The interannual variability was investigated using seasonal and monthly means. The major findings are the positive trend of the seasonal means and the prominence of variability at the interdecadal scale (12-15 yr).<br>Relationships with runoff, monthly surface air temperature, monthly air circulation, autumnal water salinity and temperature profiles, and particular climatic events are investigated to determine the major causes of the variability.<br>From the original 83-cell grid data, the monthly-averaged icefields of the Gulf were calculated and their maps generated for the months of January, February, March, April and May for every sample year.
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Highberger, Jamie Lee. "The chemistry of metal-containing molecules in the circumstellar envelopes of late-type stars: Millimeter-wave observations and abundance modeling." Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/280417.
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An intensive observational program of Asymptotic Giant Branch (AGB) and post-AGB stars has been conducted in order to investigate the role of metal-containing compounds in the circumstellar envelopes surrounding these objects. The role of metal bearing molecules in the chemical evolution of these envelopes was also examined. These studies have led to the detection of a new interstellar molecule, AlNC, as well as the first identification of metal species in two new sources. Specifically, MgNC, AlF, NaCl, and NaCN were seen for the first time towards CRL 2688 and MgNC was also detected in CRL 618. These detections, and the non-detection of metal carbide or metal nitride species, indicate that metals preferentially form cyanide complexes in circumstellar clouds. The process of formation for these species is believed to be radiative association of a metal ion with a cyanopolyne chain followed by dissociative recombination. It has also been discovered that, as a star evolves, abundances of metal molecules in the inner circumstellar envelope decrease due to photo-destruction processes or adsorption onto dust grains. A new chemical code to study molecular abundances in the inner circumstellar envelope of AGB stars has also been developed. This new chemistry code is unique in that it is the first attempt to take a kinetic approach to the equilibrium problem. A system of reactions is used as a pathway to reach equilibrium at a specified temperature and density. This new technique allows the monitoring of abundance changes over time and can be used as a foundation for non-LTE calculations. The model results were consistent with previous work and older methods. The abundances of metal halides and NaCN in the AGB phase can be explained because of equilibrium processes at temperatures less than 1600 K for moderate to high densities. The model also demonstrated that AlNC could be produced in equilibrium conditions in amounts greater than the observed abundance of this molecule in IRC+10216. Chemical changes with time were monitored and it was shown that equilibrium processes occur on timescales larger than the typical pulsational period of an AGB star. Finally, abundance predictions were made for several potential new circumstellar metal-containing molecules.
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Savage, Chandra Shannon. "Ions, isotopes, and metal cyanides: Observational and laboratory studies." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290082.
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Chemistry in the interstellar medium is very different from the processes which take place in terrestrial settings. Environments such as circumstellar envelopes, molecular clouds, and comets contain diverse and complex chemical networks. The low temperatures (10-50 K) and densities (1-10⁶ cm⁻³) allow normally unstable molecules to exist in significant quantities. At these temperatures, the rotational energy levels of molecules are populated, and thus these species can be detected by millimeter-wave radio astronomy. The detection and quantification of interstellar molecules, including metal cyanides and molecular ions, is the basis of this dissertation work. While conducting observations of CN and ¹³CN to determine the ¹²C/¹³C ratio throughout the Galaxy, it was found that the ratios in photon-dominated regions (PDRs) were much higher than those in nearby molecular clouds. This can be explained by isotope-selective photodissociation, in which the ¹²CN molecules are self-shielded. However, the chemistry in these regions is poorly understood, and other processes may be occurring. In order to understand one of the chemical networks present in PDRs, observations of HCO⁺, HOC⁺, and CO⁺ were made toward several of these sources. Previous studies indicated that the HCO⁺/HOC⁺ ratio was much lower in PDRs, due to the presence of CO⁺. The new observations indicate that there is a strong correlation between CO⁺ and HOC⁺ abundances, which suggests that other molecular ions which have not been detected in molecular clouds may be present in PDRs. There is a significant obstacle to the detection of new interstellar molecular ions, however. The laboratory spectra are virtually unknown for many of these species, due to their inherent instability. Thus, techniques which can selectively detect ionic spectra must be utilized. One such method is velocity modulation, which incorporates an AC electrical discharge to produce and detect ions. Previously, velocity modulation spectroscopy was employed only at infrared wavelengths. The final phase of this dissertation work was to design, build and test a velocity modulation spectrometer which functions at millimeter/sub-mm wavelengths. This system was then used to measure the previously unknown pure rotational spectrum of SH⁺ (X3Σ⁻).
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Unterborn, Cayman Thomas. "Before Biology: Geologic Habitability and Setting the Chemical and Physical Foundations for Life." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1461193916.
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Rao, Anupama M. N. "Titan, Triton, Pluto, and Kuiper belt objects: A study of past and present atmospheres with grey and nongrey models." Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/280020.
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This work is divided into two parts: a grey model for past Triton, Pluto, and Kuiper belt objects, and a nongrey model for current Titan's troposphere. Steady-state, planar models of early atmospheres for Triton, Pluto, and Kuiper belt objects are computed using a grey approach that tracks the transfer/distribution of heat via radiative transport. These objects are treated here together because they resemble one another in size, surface chemical composition, and exist in the same cold portion of the outer solar system. Beginning with present-day volatiles observed on the surfaces of Triton and Pluto (methane and molecular nitrogen), a trace of molecular hydrogen (present in most primordial atmospheres) is added. It is assumed that as the object is heated by solar, tidal, accretional, or radiogenic methods (this varies between the objects treated here) these chemical species then evaporate from the surface to create an atmosphere. Binary collisions among the molecules account for the sources of opacity, and absorption coefficients are provided by [21]. The grey atmosphere calculations require a mean opacity, and its results are sensitive to the type of mean opacity used. Thus a variety of methods (Planck, Rosseland, and Chandrasekhar mean opacities) are used to accommodate this dependence and the variations in optical depth. Surface temperatures are then calculated as a function of the heating rate, molecular hydrogen abundance, and mean opacity type. As a result of these modelling experiments, tidal heating is found to be crucial to the formation of a thick atmosphere on Triton, and albedo and gravitational acceleration strongly affect the formation of atmospheres on less massive objects such as Pluto and Kuiper belt objects. A nongrey, steady-state, planar model of Titan's current troposphere is developed to study the effect of varying methane mass fraction. Methods from stellar atmosphere modelling are used to solve the equation of transfer as a two-point boundary problem. To additionally satisfy radiative, hydrostatic, and local thermodynamic equilibrium, an iterative correction procedure is utilized since the correct temperature and density profiles as a function of altitude are not known a priori. The volatile composition is taken from observation: molecular nitrogen, methane, and molecular hydrogen. Again, binary collisions among the molecules account for the sources of opacity, and absorption coefficients are provided by [21]. The heating source for Titan is solar radiation absorbed and reradiated by the planet's surface in the infrared region of the spectrum, with a small amount of heat emanating from the stratosphere. The chemical species evaporate from the surface to create an atmosphere. Models of Titan's troposphere are calculated using different amounts of methane (within observational constraints) since the presence of methane is evolving in Titan's atmosphere due to photolytic processes. From model results it is shown that by solving the radiative transfer equation, subject to radiative, hydrostatic, and local thermodynamic equilibrium constraints, a model of Titan's troposphere with a maximum deviation of 8% from data [85] [170] can be obtained. The preliminary model of past Titan's troposphere is consistent with other analytic results [89].
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Pety, Jérôme. "Caractériser le milieu interstellaire : un clé pour comprendre l'Univers." Habilitation à diriger des recherches, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00726959.
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Qu'ont en commun la détection de carbone atomique à un redshift de 4, la cartographie à 1" de résolution de l'émission 12CO(1-0) de la galaxie du tourbillon (M51), l'étude des avant-plans galactiques de Planck, et l'étude de la cinématique du disque et du flot moléculaire de la proto-étoile HH30 ? Au-delà du fait qu'elles sont réalisées dans le domaine (sub-)millimétrique, ces observations sont liées aux processus physiques et chimiques du milieu interstellaire. Caractériser ces processus permet de comprendre les objets les plus divers de l'univers, des plus proches au plus lointains, des plus petits au plus grands. Je décris ici une décennie de travail consacrée à la compréhension du milieu interstellaire. Je commence par présenter deux des approches scientifiques que j'ai prises. La première concerne la caractérisition d'une des transitions les moins bien comprises du gaz dans son chemin vers la formation des étoiles, à savoir la transition HI vers H2.Je montre comment l'interprétation de l'émission 12CO(1-0) pointe tout autant vers le milieu dense et froid que vers le milieu diffus et tiède. Dans un 2ème temps, je décris la nécessité et la mise en place d'une référence observationnelle (la chevelure de la nébuleuse de la Tête de Cheval) pour les modéles photochimiques, eux-mêmes utilisés dans tous les contextes évoqués ci-dessus. La décennie qui vient sera aussi féconde grâce à plusieurs événements. Tout d'abord, la communauté qui étudie le milieu interstellaire se structure rapidement autour de grands projets. A mon niveau, je suis porteur du contrat ANR << Structure and CHemistry of the Inter-Stellar Medium >> (SCHISM) qui réunit observateurs, numériciens et théoréticiens de l'IRAM et de l'Observatoire de Paris. Par ailleurs, l'instrumentation radio fait des progrès spectaculaires qui vont déboucher sur la spectro-imagerie grand champ à haute résolution angulaire et spectrale. L'IRAM a un rôle prépondérant dans cette aventure et j'y contribue au niveau logiciel et algorithmique. Enfin, je participe à la maturation des nouveaux instruments comme les caméras grand-champs pour les antennes uniques et les projets ALMA et NOEMA en interférométrie (sub-)millimétrique. La conjonction de ces facteurs contribuera à percer à jour l'origine des galaxies, des étoiles, des systèmes planétaires et des molécules prébiotiques.