Numerous wave and gap features observed in Voyager data of Saturn's rings are produced by resonances between the orbital frequencies of known external satellites and ring particle orbits. This thesis investigates the possibility that other, currently unassociated, ring features are generated by perturbations on ring participle orbits produced by non-axisymmetric gravitational fields resulting from acoustic oscillation modes of the planet. The frequencies of Saturnian low degree (l ≤ 8) fundamental (or f) mode oscillations are calculated for a variety of Saturn interior models which span the range of uncertainty of the interior structure of the planet. Corrections for rotation, oblateness, and possible differential rotation have been applied. Only the low degree f-modes are found to have frequencies and likely wave amplitudes in the range necessary to produce gap or wave features in the rings. The calculated positions of outer Lindblad resonances (OLR) for the degree l = 2,3,4, and 5 sectoral f-modes of a single Saturn model lie near four previously unassociated C-ring features. These features are the Maxwell gap and three waves identified as being forced at either OLR or inner vertical resonances. The outer vertical resonance (OVR) of the l = 5, m = 4 mode also overlaps the location of a wave which may be forced at either an OVR or an inner Lindblad resonance. Four other similar wave features, however, cannot be explained by oscillation mode resonances. This failure to account for all of the comparable unassociated C-ring waves is the principal inadequacy of the hypothesis. Other observed properties of the wave features, however, including their azimuthal wavenumbers m and the variation of amplitude with proposed oscillation mode degree are consistent with the proposed forcing. Planetary oscillation amplitudes of ∼1 m are required for gap opening; wave amplitudes of ∼10 cm are required for density wave production. The C-ring thus serves as a very sensitive f-mode detector. Observations by the Cassini spacecraft should unequivocally determine if the C-ring features are produced by planetary oscillation modes. If these observations confirm the association, significant new constraints could be placed on Saturnian energy transport, differential rotation, and core size.

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The Cassini mission provided wonderful tools to explore Saturn, its satellites and its rings system. The UVIS instrument allowed stellar occultation observations of structures in the rings with the best resolution available (around 10 meters depending on geometry and navigation), bringing our understanding of the physics of the rings to the next level. In particular, we have been able to observe, dissect, model and test the interactions between the satellites and the rings. We first looked at kilometer-wide structures generated by resonances with satellites orbiting outside the main rings. The observation of structures in the C ring and their association with a few new resonances allowed us to estimate some constraints on the physical characteristics of the rings. However, most of our observed structures could not be explained with simple resonances with external satellites and some other mechanism has to be involved. We located four density waves associated with the Mimas 4:1, the Atlas 2:1, the Mimas 6:2 and the Pandora 4:2 Inner Lindblad Resonances and one bending wave excited by the Titan -1:0 Inner Vertical Resonance. We could estimate a range of surface mass density from 0.22 ([plus or minus]0.03) to 1.42 ([plus or minus]0.21) g cm[super-2] and mass extinction coefficient from 0.13 ([plus or minus]0.03) to 0.28 ([plus or minus]0.06) cm[super2] g[super-1]. These mass extinction coefficient values are higher than those found in the A ring (0.01 - 0.02 cm[super2] g[super-1]) and in the Cassini Division (0.07 - 0.12 cm[super2] g[super-1] from Colwell et al. (2009), implying smaller particle sizes in the C ring. We can therefore imagine that the particles composing these different rings have either different origins or that their size distributions are not primordial and have evolved differently.; Using numerical simulations for the propeller formation, we estimate that our observed moonlets belong to a population of bigger particles than the one we thought was composing the rings: Zebker et al. (1985) described the ring particles population as following a power-law size distribution with cumulative index around 1.75 in the Cassini Division and 2.1 in the C ring. We believe propeller boulders follow a power-law with a cumulative index of 0.6 in the C ring and 0.8 in the Cassini Division. The question of whether these boulders are young, ephemeral and accreted inside the Roche limit or long-lived and maybe formed outisde by fragmentation of a larger body before migrating inward in the disk, remains a mystery. Accretion and fragmentation process are not yet well constrained and we can hope that Cassini extended mission will still provide a lot of information about it.; We also estimate the mass of the C ring to be between 3.7 ([plus or minus]0.9) x 10[super16] kg and 7.9 ([plus or minus]2.0) x 10[super16] kg, equivalent to a moon of 28.0 ([plus or minus]2.3) km to 36.2 ([plus or minus]3.0) km radius (a little larger than Pan or Atlas) with a density comparable to the two moons (400 kg m[super-3]). From the wave damping length and the ring viscosity, we also estimate the vertical thickness of the C ring to be between 1.9 ([plus or minus]0.4) m and 5.6 ([plus or minus]1.4) m, which is consistent with the vertical thickness of the Cassini Division (2 - 20 m) from Tiscareno et al. (2007) and Colwell et al. (2009). Conducting similar analysis in the A, B rings and in the Cassini Division, we were able to estimate consistent masses with previous works for the these rings. We then investigated possible interactions between the rings and potential embedded satellites. Looking for satellite footprints, we estimated the possibility that some observed features in the Huygens Ringlet could be wakes of an embedded moon in the Huygens gap. We discredited the idea that these structures could actually be satellite wakes by estimating the possible position of such a satellite. Finally, we observed a whole population of narrow and clear holes in the C ring and the Cassini Division. Modeling these holes as depletion zones opened by the interaction of a moonlet inside the disk material (this signature is called a "propeller"), we could estimate a distribution of the meter-sized to house-sized objects in these rings. Similar objects, though an order of magnitude larger, have been visually identified in the A ring. In the C ring, we have signatures of boulders which sizes are estimated between 1.5 and 14.5 m, whereas similar measures in the Cassini Division provide moonlet sizes between 0.36 and 58.1 m.

Student Number : 0410864E - MSc dissertation - School of Chemistry - Faculty of Science / The aim of the project described in this dissertation is to explore the application of ring closing metathesis (RCM) to the synthesis of 6-, 7-, 8- and 9-membered N,N-, N,O- and O,O-benzo-fused heterocyclic compounds which are interesting structural motifs in medicinal chemistry. In recent times, their structures have been widely used as molecular scaffolds. Some of these heterocycles have been identified as antitumour agents, antibiotics and anti-HIV agents. In our laboratories, a variety of 6-, 7- and 8-membered nitrogen- and oxygen- containing benzo-fused rings have been synthesized through ruthenium-mediated isomerisation and RCM in moderate to good yields. The first step in the present project was N-protection of suitable 2-aminophenols or o-phenylenediamines followed by allylation. Rutheniummediated isomerisation followed by RCM was then used for the synthesis of the 6- membered ring system tert-butyl 4H-1,4-benzoxazine-4-carboxylate 91 and the 7- membered ring system tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103 while only RCM was used for the 8-membered ring systems, di(tert-butyl) 2,3,4,5-tetrahydro-1,6- benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6-benzodiazocine-1,6- dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6-benzodiazocine 132, 7-methoxy- 2,5-dihydro-1,6-benzodioxocine 137 and the 9-membered ring system 1,6-bis[(4- methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159. In the synthesis of the 7-membered ring systems, based on established methodology, we encountered problems with the RCM from suitable benzylamine or benzyl alcohol precursors. The reasons for this are not clear but we suspect this could be as a result of electronic and kinetic factors. Nevertheless, we were able to synthesize a 7-membered ring system, tert-butyl 1,5-benzoxazepine-5(4H)-carboxylate 103, from a readily available precursor using a different methodology. Approaches to the synthesis of the 8-membered ring systems, di(tert-butyl) 2,3,4,5- tetrahydro-1,6-benzodiazocine-1,6-carboxylate 130, di(tert-butyl) 2,5-dihydro-1,6- benzodiazocine-1,6-dicarboxylate 129, 1,6-dibenzoyl-1,2,5,6-tetrahydro-1,6- benzodiazocine 132 and 7-methoxy-2,5-dihydro-1,6-benzodioxocine 137, as described in this dissertation, made extensive use of RCM in moderate to good yields, but the deprotection of the Boc group after hydrogenation proved to be a problem. The synthesis of the 9-membered nitrogen containing benzo-fused compounds, 1,6- bis[(4-methylphenyl)sulfonyl]-2,5,6,7-tetrahydro-1H-1,6-benzodiazonine 159 by RCM was successful but in the synthesis of the N,O-benzo-fused compound by RCM, we suspect that polymerization, which is a side reaction in RCM reactions that are slow, occurred. In the synthesis of the 9-membered O,O-benzo-fused compounds, we only isolated the starting material. The final approach in this dissertation involved the use of ruthenium-mediated isomerisation to afford internal isomerisation of the double bond within the heterocyclic rings of the 8-membered and 9-membered benzo-fused compounds previously prepared in our laboratory. This gave a mixture of regioisomers of 10-methoxy-2,3-dihydro-1,6- benzodioxocine 163 and 7-methoxy-2,3-dihydro-1,6-benzodiazocine 164, 1,6-bis[(4- Methylphenyl)sulfonyl]-1,2,3,6-tetrahydro-1,6-benzodiazocine 166, a regioisomeric mixture of 6-[(4-methylphenyl)sulfonyl]-3,6-dihydro-2H-1,6,-benzoxazocine 161 and 6-[(4-methylphenyl)sulfonyl]-5,6-dihydro-4H-1,6,-benzoxazocine 162, and the 9- membered benzo-fused ring system, 1,6-bis[(4-methylphenyl)sulfonyl]-2,3,6,7- tetrahydro-1H-1,6-benzodiazonine 170. The yields were good and the solid state structures of these isomerised compounds were examined by X-ray crystallography. Xray diffraction was also performed on the solid state 8- and 9-membered benzo-fused ring systems. We also compared the crystal structures of the 8- and 9-membered benzo-fused compounds with their isomerised compounds.

The two Voyager spacecraft discovered small-scale, radially-extended features in the central region of Saturn's B Ring. These "spokes" are "clouds" of submicron-size ice grains which are electrostatically levitated above the ring plane and which appear to travel about Saturn in Keplerian orbits (Smith et al., 1981, Science 212, 163-191). This research project is a study of the dynamical and physical properties of spokes as deduced from Voyager Saturn ring images. An analysis of the orbital motion of two dynamically-anomalous spokes, in particular, has set limits on the charge-to-mass ratios of spoke particles at various times during their dynamical evolution. These two spokes have charge-to-mass ratios of at least -60 ± 3 C kg⁻¹ while corotating with Saturn, and charge-to-mass ratios of no more than -22 ± 2 C kg⁻¹ while orbiting Saturn at Keplerian velocities. Additionally, charge decay on the grains of these spokes, caused by solar UV photoemission, has allowed a lower limit of 0.10 ± 0.03 μm to be placed on the range of radii for spoke particles. In a study of spoke photometry, a single-scattering analysis of the 0.470-μm phase function for spokes has set a mean radius for the dominant scatterers (at this wavelength) of 0.22 ± 0.02 μm. Also, a multispectral analysis of spokes has determined the spectral index of the size distribution for spoke particles to be 2.1 ± 0.2. These dynamical and physical properties of spokes have been combined with theoretical explanations of spoke activity to develop a phenomenological model of spoke formation and evolution. The transport of angular momentum within the rings due to the radial motion of spoke grains is shown to be the most significant effect of spoke activity on the dynamical evolution of the B Ring, as was predicted by Goertz et al. (1986, Nature 320, 141-143). The radial mass transport velocity due to highly-charged spokes is -1 x 10⁻⁹ m s⁻¹. The subsequent spreading time for the B Ring is 600 million years, which is significantly less than the 4.6 billion-year age of the solar system.

Orientador: Rafael Sfair de Oliveira / Resumo: A estrela PDS110 (HD290380) com idade aproximada de 10 milhões de anos, apresentou dois eclipses ocorridos em 2008 e 2011, com duração de 25 dias e queda de aproximadamente 26 % na luminosidade da estrela. Outra estrela J1407 (1SWASP J140747.93-39454.6) apresentou uma complexa série de eclipses com 56 dias de duração. As hipóteses dadas a esses dois eventos foram a passagem da borda de um disco planetário ou um disco circunstelar de uma anã marrom. Neste trabalho foi analisada a natureza desses possíveis sistemas de anéis ao redor de um exoplaneta gigantesco não observado, que teria ocultado essas estrelas. Para estudar o sistema PDS110b, devido ao grande número de variáveis envolvidas ainda desconhecidas neste problema como, por exemplo, massa e excentricidade do planeta, inclinação e extensão do disco, foram criados diversos modelos numéricos considerando a interação gravitacional entre a estrela, o planeta e a partícula do anel. Desta forma foi possível refinar os intervalos dos parâmetros predeterminados através dos dados observacionais, que seriam compatíveis com o eclipse observado. Os resultados indicam que provavelmente os eclipses teriam ocorrido por um planeta com massa entre 50 e 70 MJup, em uma orbita quase circular (ePDS110b < 0,05) e o semieixo maior de 2 ua. O sistema de anel ao redor do PDS110b, teria uma extensão radial de ~ 0,2 ua, significativamente maior que o raio de Roche do planeta e um forte indicio da presença de satélites. Ao analisar o sistema de an... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The star PDS110 (HD290380) is approximately 10 millions years old, underwent two eclipses observed in 2008 and 2011 in the surrounding 25 days with a depth 26 % in the star's luminosity. Other star J1407 (1SWASP J140747.93-39454.6) underwent a complex series of eclipses that lasted 56 days. The hypothesis could explain those events are the transit of the edge one disc circumplanetary or circumstelar (brown dwarf). In this work, we analyzed the nature of a possible ring system around these giant exoplanets would have occulted the star. To study the PDS110b system, in the reason to the large number of unknown variable involved in this problem like: mass and the eccentricity of the PDS110b, inclination and size of the disc, we created a several numerical models considering the only gravitational interactions between the star, the planet and the particle of the ring. We managed to restrict the interval of the parameters predetermined by the observational data. The best models indicate a planet's mass between [50 - 70] MJup, in the quasi circular orbit (ePDS110b < 0,05) and semi major axis of 2 ua. The ring system around the PDS110b, probably has ~ 0,2 ua of radial extension. To analyze the ring system around J1407b, after excluded some proposals of the eclipsing body to be a secundary star, the studies propose an extensive ring system with radius of 0,6 ua, formed by at least 37 different rings and one possible exomoon with mass proportional to Earth, located at the gap observed ... (Complete abstract click electronic access below) / Mestre

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22272号 / 理博第4586号 / 新制||理||1658(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)教授 大須賀 篤弘, 教授 依光 英樹, 教授 時任 宣博 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

The proteasome, a multiprotease complex, is clinically validated as an anticancer target by the FDA approval of bortezomib and carfilzomib for the treatment of multiple myeloma. The emergence of resistance to proteasome inhibitors however remains a major clinical challenge. Recently, distinct types of proteasomes termed ‘intermediate proteasomes’, which contain unconventional mixtures of catalytic subunits, have been implicated with drug resistance of tumor cells. In elucidating the role of intermediate proteasomes in drug resistance, a crucial step is to unequivocally determine the subunit composition of intermediate proteasomes in cells. With this in mind, the goal of the studies reported in this dissertation is to develop novel chemical tools which can facilitate the investigation of intermediate proteasomes via two complementary approaches: a FRET-based approach and a bifunctional cross-linking approach. Chapter 2 describes the structure-based design, synthesis, and characterization of a peptide epoxyketone-based fluorescent probe, named as LKS01-B650, which selectively targets the immunoproteasome subunit β5i/LMP7. In addition to its utility in determining the identity of intermediate proteasomes as FRET-based probe, this imaging agent may also serve as a valuable tool in visualizing the immunoproteasome in living cells. Chapter 3 describes the design and synthesis of various epoxyketone-based bifunctional agents. The ability of these bifunctional agents to cross-link different catalytic subunits within a proteasome complex is shown by mobility shift assays.These bifunctional agents may provide important information in determining the subunit composition of proteasomes. Chapter 4 describes a systematic study of the relationship between the proteasome inhibitor structure and the inhibitory activity against critical subunits of the proteasome. Given the reported role of β5i/LMP7 in autoimmune diseases, this study may provide useful insights in developing therapeutic agents for autoimmune diseases as well as other diseases. Chapter 5 describes a separate study which is not related to proteasome biology. A concise approach to synthesize 1-azaspirocyclic ring systems is developed by utilizing a novel semi-pinacol/Beckmann rearrangement. Additionally, an environmentally benign, microwave-assisted, and solvent-free self-condensation of carbonyl compounds is reported.

[Truncated abstract] This thesis examines the bonding interactions and chemical processes associated with irradiated water (H2O) and ammonia (NH3) molecules. The experiments conducted in the present study are designed to replicate the surface chemistry of outer Solar System bodies, particularly the icy surfaces of Saturn's inner moons. Infrared (IR) spectroscopy is used to identify the H2ONH3 complex isolated in an argon (Ar) matrix. An electric discharge is then applied to the H2O and NH3 species to produce the hydroxyl-ammonia (OHNH3) complex and the water-amidogen (H2ONH2) complex. Finally, the ammonia-oxygen (NH3O2) complex is formed in an Ar matrix, complementing previous studies performed by the Quickenden research group, which investigated the conversion of OH radicals into molecular O2 on icy planetary surfaces. ... An electric discharge is applied to the NH3 in Ar mixture, producing the NH2 radical subunit of the complex. Two absorption bands are assigned to the H2O subunit vibrational frequencies of the complex; at 1616.1 cm-1 for the ¿2 HOH bending fundamental and at 3532.1 cm-1 for the ¿1 OH bonded stretching fundamental. Two absorption bands are also assigned to the NH2 radical subunit vibrational frequencies of the complex; at 1498.5 cm-1 for the ¿2 HNH bending fundamental and at 3260.8 cm-1 for the ¿3 NH asymmetric stretching fundamental. These assignments are verified by the isotope substitution method, involving the formation of the deuterated D2OND2 complex analogue in an Ar matrix and the measurement of the isotope induced shifts in peak position in the IR region. The isotopic shifts displayed by the IR absorption bands are in good agreement with the theoretically calculated shifts in vibration frequency when going from the H2ONH2 complex fundamentals to the D2OND2 complex fundamentals. The theoretical calculations also derived an interaction energy of 5.2 kcal mol-1 for the HOHNH2 structure of the H2ONH2 complex. This HOHNH2 structure is also confirmed as the preferred structure of the H2ONH2 complex in the IR experiments, by the observation of a large shift in position of the absorption band associated with the H2O subunit ¿1 OH stretching fundamental, away from the position of the H2O monomer ¿1 OH stretching fundamental. This indicates that the H2O subunit donates a hydrogen for the complex bond in the HOHNH2 complex. The NH3O2 complex is identified in solid Ar matrices at 10.5 K by IR analysis. The NH3O2 complex is formed by the co-deposition of gaseous NH3 in Ar mixtures with O2 in Ar gas mixtures. An absorption band is assigned to the ¿1 OO stretching fundamental for the O2 subunit of the NH3O2 complex at 1552.0 cm-1. This assignment is verified by the isotope substitution method, involving the formation of the deuterated ND3O2 complex analogue in an Ar matrix and the measurement of the isotope induced shift in peak position in the IR region. The isotopic shift displayed by the IR absorption band is in good agreement with the theoretically calculated shift in vibration frequency when going from the NH3O2 complex fundamental to the ND3O2 complex fundamental. The theoretical calculations also derived an interaction energy of 0.28 kcal mol-1 for the NH3O2 complex.