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1
Kahui, Dennis Jon. "A cultural approach to music therapy in New Zealand : a Maori perspective : a dissertation presented in partial fulfilment of the requirements for the degree of Master of Music Therapy at Massey University, NZ School of Music, Wellington, New Zealand." Massey University, 2008. http://hdl.handle.net/10179/898.
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The main theme of this study is to form a culturally appropriate approach to music therapy concepts from a Maori perspective that could be inclusive and accommodate both Maori and Tauiwi (non-Maori) Rangatahi (adolescents) in health care settings. In order to provide a descriptive account of the holistic aspects of introducing Maori musical concepts in a music therapy setting a qualitative design was employed. The study draws on my personal journal entries, an interview with Kaumatua (Maori respected elders) regarding the appropriateness of introducing and altering traditional Maori musicality to accommodate the patient’s needs and a case study involving the Haka as a music therapy intervention strategy with a young Maori patient diagnosed with schizophrenia. My findings show that as a music therapist consultation with Kaumatua regarding anything related to Maori cultural aspects was essential. I also found that when working with a Maori Rangatahi who is immersed in Maori culture, it created an atmosphere of containment, familiarity, enjoyment, engagement and an environment that facilitated the achievement of therapeutic goals. Te Whare Tapa Wha Maori mental health model is well suited as a music therapy assessment tool to the characteristics of the physical, emotional, spiritual and family context of the Haka. I also found that Tauiwi music therapists wishing to introduce cultural elements must first learn about Maori culture and the people in order to confidently understand the music. Tauiwi Rangatahi may also benefit from the introduction of Maori musicality as a therapeutic means by being an inclusive member of the community and the positive psychological effects. For example, Rangatahi benefited from learning the proper pronunciation and meaning of the Haka, which in turn gave them a sense of achievement. I also found that some Maori protocols fit well with the protocols of music therapy, such as the beginning and endings with a hello and goodbye song.
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Willgrén, I.-L. (Iina-Lotta). "Dupuytrenin tauti." Master's thesis, University of Oulu, 2018. http://jultika.oulu.fi/Record/nbnfioulu-201803021287.
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Tiivistelmä. Dupuytrenin tauti on kämmenkalvon hyvänlaatuinen sidekudossairaus, joka aiheuttaa sormia koukkuun taivuttavan sidekudosjuosteen. Koukkuun taipuneet sormet voivat pahimmillaan aiheuttaa käteen alentuneen toimintakyvyn. Dupuytrenin tauti on pääosin valkoihoisten miesten tauti, jonka riskitekijöitä vaikuttaisivat olevan ikä, perimä, diabetes, tupakointi ja alkoholin suurkulutus. Dupuytrenin tautiin ei ole parantavaa hoitoa, vaan käden toimintakykyä pyritään parantamaan poistamalla kurovaa juostetta leikkauksin tai katkaisemalla juoste kollagenaasia pilkkovalla injektiovalmisteella. Tässä tutkimuksessa pyrimme selvittämään leikkaushoidon ja Xiapex-pistoshoidon komplikaatioiden yleisyyden kolmen kuukauden seurannassa. Tutkimus toteutettiin perehtymällä Oulun yliopistollisen sairaalan kirurgian poliklinikalla aikavälillä 21.9.2011–31.12.2016 käyneiden potilaiden asiakirjoihin. Tutkimustulokset olivat selviä; Xiapex-pistoshoidon saaneilla komplikaatioita oli huomattavasti vähemmän kuin leikkaushoidon saaneilla. Leikkaushoidossa komplikaatioiden yleisyys oli 43,8% ja pistoshoidolla 6,0%. Vakavia, kädentoimintakykyyn vaikuttavia komplikaatioita oli kuitenkin kummassakin ryhmässä vain yksittäisiä. Tutkimuksen ongelmana oli se, että pistoshoidon saaneiden taudinkuva oli usein lievempi ja osalla leikkaushoitoon päätyneistä oli aikaisemmin tehtyjä toimenpiteitä, pistoshoitoja tai taudinkuva oli vaikempi.
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Sorvali, M. (Mikko). "Kienböckin tauti." University of Oulu, 2015. http://urn.fi/URN:NBN:fi:oulu-201508041903.
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Tämän tutkielman aiheena oli Kienböckin tauti. Tutkimus tehtiin käsikirurgian klinikalle käsikirurgi Marko Sunnarin ohjauksessa. Tässä tutkimuksessa oli potilasmateriaalina Oulun yliopistollisessa sairaalassa Kienböckin taudin takia hoidetut potilaat vuosien 2000–2010 välillä. Tavoitteena oli tutkia hoidon kulkua sekä hoidon onnistumista, huomioida mahdollisten tunnettujen riskitekijöiden esiintyvyys potilasaineistossa, selvittää hoidon pitkäaikaistulokset (yli 2 vuotta) sekä Kienböckin taudin vaikeusaste diagnoosihetkellä. Erityisesti huomiota kiinnitettiin revaskularisaatio- ja salvageleikkaushoitojen eroihin seurannan aikana.
Aineistona toimii edellämainitulla aikavälillä hoidetut 43 potilasta. Heistä kerättiin potilasasiakirjojen perusteella tietoja: nimi, henkilöturvatunnus, sosiaaliturvatunnus, ammatti, ikä hoitoon hakeutuessa, tupakointi, dominoiva käsi, sairastunut käsi, ranteen liikkuvuus ennen ja jälkeen leikkauksen, suunniteltu hoito, toteutunut hoito, jonotusaika, jatkotoimenpiteet, preoperatiiviset tutkimukset, toipumisaika, taudin vaikeusaste hoitoon hakeutuessa, ulnaarivarianssi ja aiemmat käsien vammat. Pienen potilasaineiston takia tilastollisesti merkittäviä tuloksia ei saatu, mutta saatuja tuloksia käsiteltiin silti esimerkiksi vertailemalla tässä tutkimuksessa tulleita tuloksia aikaisempiin, kirjallisuudesta löydettyihin tuloksiin.
Tärkeimpinä tutkimustuloksina voidaan pitää molemminpuolisen Kienböckin taudin esiintyvyyttä potilasaineistossa. Lisäksi leikkaushoitoina ei tehty radiuksen lyhennysosteotomioita, mikä nykytiedon valossa vaikuttaa perustellulta ratkaisulta, koska negatiivista ulnaarivarianssia ei pidetä merkittävänä tekijää taudin synnyssä. Näin pystyttiin vertailemaan revaskularisaation ja salvagetoimenpiteiden eroja seurannan aikana. Tulosten mukaan revaskularisaatiolla hoidetut potilaat joutuvat useammin uusintatoimenpiteeseen, toipumisajat ovat pidemmät, ja hieman pienempi osa pystyi palaamaan entiseen työhönsä.
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Akers, Eric Michael. "Aldebaran (Alpha Tauri)." [Huntington, WV : Marshall University Libraries], 2008. http://www.marshall.edu/etd/descript.asp?ref=870.
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Joncour, Isabelle. "Imagerie Doppler des étoiles T Tauri." Phd thesis, Université Paris-Diderot - Paris VII, 1994. http://tel.archives-ouvertes.fr/tel-00725018.
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Dans ce travail de thèse, nous analysons pour la première fois à l'aide de la technique d'imagerie doppler, les raies photosphériques de deux étoiles T Ttauri à faibles raies d'émission, pour cartographier leur brillance de surface et localiser ainsi les inhomogenéités en température, qui signent la présence de forts champs magnétiques. Pour ce faire, nous avons développé une méthode numerique fondée sur la paramétrisation de taches, dont les caractéristiques sont déterminées lors de la minimisation, de type moindres carrés, des différences entre les modèles de raie calculés et l'ensemble des raies (issues de divers éléments chimiques) observées à plusieurs phases rotationnelles. Nous étudions le type et l'amplitude de déformations engendrées par la présence de taches froides, ce qui nous permet d'en déduire les conditions optimales d'application de l'imagerie doppler. Nous etudions par ailleurs les limitations intrinséques de cette technique déterminées par la qualité des données (résolution instrumentale et rapport signal sur bruit). L'application à des étoiles T Tauri, jeunes étoiles en fin de formation, similaires au soleil dans sa jeunesse, nous permet de mettre en évidence la présence de larges taches froides, préférentiellement localisées aux latitudes élevées. La position de ces taches suggère une géometrie de type dipolaire pour le champ magnétique. Seule une étude exhaustive pourra déterminer si cette géometrie est commune à toute cette classe d'étoiles, ou si elle est liée à des caractéristiques particulières (fort taux de rotation 70km/s ; 80 km/s). cette réponse est cruciale pour déterminer l'origine du champ magnétique : fossile, engendré par un mecanisme particulier de type dynamo, peut-etre les deux à la fois. L'application future de cette technique aux etoiles T Tauri classiques, supposées etre entourées d'un disque d'accrétion, sera determinante pour comprendre l'interaction entre l'environnement circumstellaire et l'objet central.
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Smith, Kester William. "Accretion mechanisms in T Tauri systems." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627592.
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JONCOUR, ISABELLE. "Imagerie doppler des etoiles t tauri." Paris 7, 1994. http://www.theses.fr/1994PA077352.
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Dans ce travail de these, nous analysons pour la premiere fois a l'aide de la technique d'imagerie doppler, les raies photospheriques de deux etoiles t tauri a faibles raies d'emission, pour cartographier leur brillance de surface et localiser ainsi les inhomogeneites en temperature, qui signent la presence de forts champs magnetiques. Pour ce faire, nous avons developpe une methode numeriaue fondee sur la parametrisation de taches, dont les caracteristiques sont determinees lors de la minimisation, de type moindres carres, des differences entre les modeles de raie calcules et l'ensemble des raies (issues de divers elements chimiques) observees a plusieurs phases rotationnelles. Nous etudions le type et l'amplitude de deformations engendrees par la presence de taches froides, ce qui nous permet d'en deduire les conditions optimales d'application de l'imagerie doppler. Nous etudions par ailleurs les limitations intrinseques de cette technique determinees par la qualite des donnees (resolution instrumentale et rapport signal sur bruit). L'application a des etoiles t tauri, jeunes etoiles en fin de formation, similaires au soleil dans sa jeunesse, nous permet de mettre en evidence la presence de larges taches froides, preferentiellement localisees aux latitudes elevees. La position de ces taches suggere une geometrie de type dipolaire pour le champ magnetique. Seule une etude exhaustive pourra determiner si cette geometrie est commune a toute cette classe d'etoiles, ou si elle est liee a des caracteristiques particulieres (fort taux de rotation 70km/s ; 80 km/s). Cette reponse est cruciale pour determiner l'origine du champ magnetique : fossile, engendre par un mecanisme particulier de type dynamo, peut-etre les deux a la fois. L'application future de cette technique aux etoiles t tauri classiques, supposees etre entourees d'un disque d'accretion, sera determinante pour comprendre l'interaction entre l'environnement circumstellaire et l'objet central.
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Shenton, Mervyn. "Multiwavelength study of RV Tauri stars." Thesis, Keele University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304453.
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Worrell, John Kingsley. "Stellar pulsation and the RV Tauri phenomenon." Thesis, University of St Andrews, 1985. http://hdl.handle.net/10023/6509.
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On the basis of observational data it is argued that RV Tauri variables, and probably yellow semiregular (SRd) variables, are closely related in every way to type II cepheid stars. Assuming that a single mass (~O.6 M~) is applicable to all three classes of star linear, nonadiabatic pulsation models are calculated. Using these models, the observed effective temperatures, and periods for these stars new luminosities are calculated and compared with the observed luminosities. This comparison appears to confirm the relationships between the three classes implied by the observations for the globular cluster stars. It is shown that an interaction of two or more pulsation modes could be responsible for the characteristic light curves of the RV and SRd stars but it is argued that this is unlikely. One RV star and a high luminosity F star both exhibit pulsations with two periods. The periods together with the observed effective temperatures and linear pulsation calculations yield masses and luminosities for the two stars. On the basis of the linear pulsation calculations the peculiar characteristics of the pulsations are explained. A sequence of nonlinear pulsation models based on the "standard" physics is presented. The light curves for some of these models show features characteristic of the RV stars. Strange behaviour found in the luminosity at the surface of some models is shown to be a product of an inadequate boundary condition. An alternative is suggested which cures the problem. Nonlinear models calculated with the new boundary condition eject matter, form very extended atmospheres, exhibit semiregular RV - like light curves with a (possibly) cyclic variation of the phase of light minima, and show long term variations of mean effective temperature. strong shock waves exhibiting properties like those found in RV stars are found. It is suggested that the equilibrium diffusion approximation is inappropriate for these models and the consequences of its use discussed.
10
Kunnas, K. (Kari). "Alzheimerin tauti ja insuliiniresistenssin osuus taudin kehityksessä." Bachelor's thesis, University of Oulu, 2016. http://urn.fi/URN:NBN:fi:oulu-201606072464.
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Alzheimerin tauti on muistia ja kognitiota heikentävä hermoston rappeutumissairaus. Sen oireisiin kuuluu aivojen insuliiniresistenssi, jonka osuus Alzheimerin taudin kehittymisessä on tutkielmani kohteena. Insuliiniresistenssi heikentää aivojen energiatasapainoa, mikä johtaa vaurioihin hermosoluissa ja mahdollisesti solujen kuolemaan. Tyypin 2 diabetes ja ei-alkoholiperäinen rasvamaksa voivat johtaa insuliiniresistenssin muodostumiseen aivoissa. Lisäksi vaikuttaisi siltä, että viime vuosikymmeninä ravinnossa yleistyneet nitrosoamiinit lisäävät aivojen insuliiniresistenssiä. Tulevaisuudessa häiriöitä aivojen insuliinin toiminnassa pyritään näillä näkymin parantamaan nenän kautta hengitettävällä lisäinsuliinilla sekä muilla, vielä kehitysvaiheessa olevilla, lääkkeillä.
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Wahlgren, Glenn Michael. "A spectral analysis of RV Tauri variables /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu148726636233899.
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Bouvier, Jerome. "Rotation et activité dans les étoiles T Tauri." Phd thesis, Université Paris-Diderot - Paris VII, 1987. http://tel.archives-ouvertes.fr/tel-00725122.
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Le but de ce mémoire est de poser les jalons qui permettront d'identifier les sources d'énergie et les mécanismes physiques qui sont responsables de l'activité manifestée par les étoiles T Tauri. Dans le contexte offert par l'étude de l'activité des étoiles de type solaire, il s'agit ici de déterminer dans quelle mesure l'analogie solaire peut être appliquée à l'activité manifestée par les étoiles T Tauri. Cette démarche qui consiste à différencier les sources d'énergie dont disposent ces étoiles constitue une première étape vers leur identification. Le Chapitre 1 constitue un rappel des propriétés des étoiles T Tauri (1.2), des modèles théoriques qui s'y rapportent (1.3), et des sources d'énergie dont elles peuvent bénéficier (104). L'existence de champs magnétiques à la surface des étoiles T Tauri est établie dans le Chapitre II : en premier lieu, la détection de variations périodiques dans les courbes de lumière de 11 étoiles T Tauri y est rapportée (II.2.1) ; les variations photométriques périodiques sont interprétées en terme d'une distribution de température hétérogène à la surface des étoiles (11.2.2, 11.2.3) ; le développement (II.2A) et l'application (II.2.5) d'un modèle théorique visant à reproduire les courbes de lumière observées permettent ensuite de déduire les propriétés physiques et géométriques de cette distribution; finalement, la présence de champs magnétiques photosphériques à la surface des étoiles T Tauri, premier indice de l'existence d'un processus dynamo, est déduite de la comparaison des propriétés de cette distribution avec celles des taches magnétiques couvrant la surface des systèmes RS CVn (II.2.6). Le rôle du processus dynamo dans le chauffage non-radiatif de l'atmosphère des étoiles T Tauri est étudié dans le Chapitre III : pour ce faire, après avoir discuté les paramètres qui semblent au mieux refléter le niveau d'activité stellaire et l'efficacité du processus dynamo (III.2), le comportement des étoiles T Tauri est analysé dans des diagrammes activité-rotation et comparé à celui des étoiles de type solaire (III.3) , L'existence du processus dynamo y est établie et ses limites cernées, Les implications de ces résultats sur la physique du processus dynamo dans les étoiles complétement convectives sont abordées (III.4.1) et, après une analyse détaillée des différences existant entre l'atmosphère des étoiles T Tauri et celle des étoiles de type solaire (III.4.2), les résultats obtenus sont confrontés aux prévisions des modèles théoriques (III.4.3) ; finalement, l'accrétion de matière circumstellaire à la surface des étoiles est présentée comme une source d'énergie susceptible de suppléer le processus dynamo (III.4.4). Deux appendices, présentés sous la forme de publications parues dans Astronomy and Astrophysics, complètent cette étude. L'appendice A décrit l'analyse et l'interprétation de la courbe de lumière périodique de l'étoile DN Tauri, un membre représentatif de la classe des étoiles T Tauri. Cette appendice se rapporte directement au Chapitre II. L'ensemble de l'étude présentée dans ce mémoire repose sur la détermination précise des taux de rotation d'un échantillon statistiquement significatif d'étoiles T Tauri. Cette détermination, qui fut notre première tache, est décrite dans l'appendice B. Le lecteur y trouvera un exposé détaillé des différentes méthodes utilisées pour mesurer les taux de rotation de ces étoiles peu lumineuses. En outre, les résultats obtenus y sont analysés dans le cadre du problème de l'évolution du moment angulaire durant les phases pré-séquence principale.
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Bouvier, Jérôme. "Rotation et activité dans les étoiles T Tauri." Paris 7, 1987. http://www.theses.fr/1987PA077021.
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Étude de l'évolution du moment angulaire par la détermination du taux de rotation de 28 étoiles jeunes du type T Tauri. Recherche des signes d'une activité d'origine magnétique dans ces étoiles de faible masse. Les variations lumineuses périodiques peuvent être interprétées par des taches à leur surface créées par la présence de champs magnétiques photosphériques. L’accrétion de matière interstellaire à leur surface est susceptible d'expliquer d'autres aspects de l'activité manifestée par ces étoiles.
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Bouvier, Jérôme. "Rotation et activité dans les étoiles T Tauri." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37603384s.
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Kasper, Markus Erdmann. "Optimierung einer adaptiven Optik und ihre Anwendung in der ortsaufgelösten Spektroskopie von T Tauri." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961620153.
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Ratzka, Thorsten. "High spatial resolution observations of young stellar binaries." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975232703.
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Bubar, Eric Joseph. "Keck HIRES spectroscopy of candidate post T Tauri stars." Connect to this title online, 2007. http://etd.lib.clemson.edu/documents/1181666291/.
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Gregory, Scott G. "T Tauri stars : mass accretion and X-ray emission." Thesis, St Andrews, 2007. http://hdl.handle.net/10023/336.
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Armitage, P. J. "Accretion discs in T Tauri stars and interacting binaries." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596148.
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This thesis explores aspects of the theory of accretion discs in two astrophysical environments; around young low-mass stars - T Tauri stars, and in mass transfer binaries. A particular aim is to consider the role that magnetic fields - including fields within the disc and those of the central star - may play in controlling the evolution of the star-disc system. T Tauri stars are known to be magnetically active, and the first part of the thesis considers the structure and evolution of discs around magnetic T Tauri stars. I extend prior models to examine the effect of time-varying magnetic fields on the disc, and show that some of the long-term photometric variability in T Tauri systems could be caused by the influence of magnetic cycles on the accretion disc. The evolution of the star-disc system on much longer timescales is then investigated by combining pre-main-sequence stellar evolution models with those for the disc. The resulting model is used to examine the rotation rates of magnetically braked T Tauri stars, and the possible influence of close binary companions on those rotation rates. The second part of the thesis considers accretion discs in interacting binary systems. A magnetic dynamo within the disc is a promising candidate mechanism for the origin of the viscosity in accretion discs, and I discuss the implications of an operating dynamo for observations of dwarf novae. A simple model is presented in which the prominent outbursts seen in these systems have a direct origin in the physics of the underlying disc dynamo. I also present the results of three dimensional simulations of the interaction between the gas stream from the mass-donating star and the accretion disc. The hydrodynamic calculations show that a significant fraction of the stream gas can ricochet off the outer rim of the disc and overflow towards smaller radii, and the implications of this for models and observations of Cataclysmic variables and low-mass X-ray binaries are discussed.
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Koerner, David Sargent Anneila Isabel Sargent Anneila Isabel. "The kinematics of circumstellar disks around T Tauri stars /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-10312007-162008.
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Sousa, Alana Paixao de. "Aquecimento em colunas de acreção de estrelas T Tauri." Universidade Federal de Minas Gerais, 2011. http://hdl.handle.net/1843/JCBV-8PBHRJ.
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Young low mass stars that show signs of accretion, the classical T Tauri stars (CTTSs), present a significant number of emission lines in their spectra. These emission lines, thought to be produced in accretion columns, are often modelled in order to obtain physical parametersof the star-disk system, such as the mass accretion rate. However, the temperature structure of accretion columns is still poorly understood. In this work, we present a study of the temperature profile of accretion columns found around CTTSs. We consider young stellar objects (~106 year) of low mass (M* ~ 2 M), which have accretion disks in keplerianrotation. We adopt a magnetospheric accretion model, where the central star has a dipole magnetic field that disrupts the disk at a distance from the star (rtr 0.1 AU) near the co-rotation point. The accreting gas follows stellar magnetic field lines from rtr to the central star. In order to determine the temperature profile in the accretion column, weuse the first law of thermodynamics, solved for the hydrogen atom in a steady state. This result gives us the heat equation, which was solved with the rate equation for the hydrogen atom, considering the processes of collisional excitation and de-excitation (with protons and electrons), radiative recombination, spontaneous transition, collisional ionization and photoionization. We use adiabatic compression as a heating mechanism, following Martin (1996), but we also analyze heating by X-rays, coming from the star. We consider as cooling mechanisms emission by Ca II and Mg II lines and bremsstrahlung. We then obtain thetemperature structure for acrretion funnels and the main physical processes which heat and cool the gas. We also found that the accretion rate of mass and the X-ray luminosity, are the most important parameters for the thermal structure of gas.Estrelas jovens de baixa massa que ainda mostram sinais de acreção, ou seja, estrelas T Tauri clássicas (ETTCs), apresentam um número significativo de linhas de emissão em seu espectro. Essas linhas de emissão são produzidas em colunas de acreção e são modeladas para obter parâmetros físicos do sistema disco-estrela, tal como a taxa de acreção de massa. No entanto, a estrutura de temperatura das colunas de acreção ainda está em aberto. Apresentamos neste trabalho um estudo do perfil de temperatura destas colunas encontradas em torno de ETTCs. Consideramos objetos estelares jovens (~10? anos) e de baixa massa (M* 2 Msol, que têm disco de acreção em rotação kepleriana. Adotamos um modelo de acreção magnetosférica, onde a estrela central tem um campo magnético de dipolo que interrompe o disco em uma distância de alguns raios estelares (rtr 0.1 UA) desde a estrela, perto do raio de co-rotação. A acreção do gás segue as linhas de campo magnético estelar desde rtr até a estrela. Para determinarmos o perfil de temperatura no funil, usamos a primeira lei da termodinâmica resolvida para o átomo de hidrogênio em um estado estacionário. Este resultado nos fornece a equação de calor que foi resolvida, juntamente com as equações de taxas para o átomo de hidrogênio, considerando os mecanismos de excitação e desexcitação colisional (com prótons e elétrons), recombinação radiativa, transição espôntanea, ionização colisional e fotoionização. Usamos como processos de aquecimento, a compressão adiabática estudada por Martin (1996) e também o aquecimento por raios-X, proveniente da estrela central, e como mecanismo de resfriamento consideramos as linhas de CaII e MgII e bremsstrahlung. Com esses mecanismos, determinamos a estrutura de temperatura para as colunas de acresção e os principais processos físicos que aquecem e resfriam o gás. Encontramos também que a taxa de acreçõo de massa e a luminosidade de raios-X, são os parâmetros de maior importância para o perfil de temperatura.
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Procópio, Lilian Costa. "Auto-ecologia de espécies de couratari (Lecythidaceae): uma abordagem para o manejo e conservação." Instituto Nacional de Pesquisas da Amazônia, 2010. http://localhost:8080/tede/handle/tede/2016.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
Fundação de Amparo à Pesquisa do Estado do Amazonas - FAPEAM
“Tauaris” are trees which belong to Lecythidaceae and are among the most logged timber species of Amazonia. However, their auto-ecology is poorly known, partly due to the use of only a few local names for all the species. This study defines, firstly, tauari species that occur in non-flooded forests of Amazonia and their patterns of abundance and geographic distribution. Then it characterizes regeneration aspects through functional morphology and biometry of fruits and seeds and germination physiology. Finally, the study defines the growth strategies of trees (DBH>10 cm). Data from herbaria and from >400 ha of inventory throughout the Amazonian biome were used to characterize the geographic ranges and the species abundances. Morpho-functional descriptions of fruits and seeds were based on material collected from trees of Central Amazonia (Manaus and Belterra, Brazil). The morphology of germination was described from experiments in the nursery. The physiology of germination was based on tests of seed tolerance to dessication, photoblastism and germination at different constant temperatures between 15 and 35 ° C. Growth strategies were defined through anual growth rates (average and maximum) based on 25-years monitoring in two forests logged under several cutting intensities (Paracou, French Guina; Belterra-Pará, Brazil). The tauari group consists of 14 species of the three genus. Nine were invetoried in the study areas. Couratari guianensis has the largest geographic range and is most frequent in inventories, however always with low densities (<1 tree/ha). Couratari stellata, C. multiflora, C. oblongifolia and Cariniana micrantha showed large geographical ranges (>1.10^6 km2), high frequencies and medium/high densities. Couratari atrovinosa, C. longipedicellata and C. tauari showed low abundances and regional or restricted ranges. The study provides new information about carpologia of poorly collected species (C. atrovinosa, C. tauari, C. longipedicellata) and the first description of the fruit of C. atrovinosa. For five simpatric Couratari species fo Central Amazonia, biometric measurements pointed out the need for a revision of the sections and / or a the variables of the fruit that determine each section. The slow drying of the fruit allows a gradual dispersal of seeds, unique among Lecythidaceae. Seedlings of the five Couratari species with foliaceous cotyledons and photosynthetic reserves in the hypocotyl are a rare morpho-functional type. The hypocotyl, folded below the insertion of the cotyledons, is a type that was still not documented. The seeds of each species showed desiccation tolerance, since germinated after reaching 7.9%, or less, of seed water content. Germination occurred in light and dark. C. guianensis and C. stellata had high germination rates at constant temperatures between 15 to 35 °C while C. longipedicellata and C. atrovinosa germinated significantly less below 20 °C and above 25 °C. The five species can be separated by the seed dispersal period (dry or rainy season). Temperature of 25 °C was appropriate for evaluation of seed quality of the five species. The group has characteristics that help management of seeds and species propagation species such as desiccation tolerance, fast germination, in every light conditions and temperature of 25 °C appropriate for seed quality evaluation. Growth strategies, described for Couratari guianensis, C. multiflora and C. stellata, were specific to each one and related to wood density and maximum size of the adults. C. stellata, emergent, had a weak growth potential (GP) in sub-canopy and much higher above (DAP 10-19 cm: 4 mm/ano; >30 cm: 16 mm/ano) and high growth rates for the largest adults (dbh>30 cm; 4,6-5,9 cm/year). In contrast, C. multiflora, lower canopy species, had a GP negatively correlated to tree size and the lowest average growth rate for adults (dbh>30 cm; 1,8-2,3 mm/year). Logging stimulated the growth of the three species during 15 years and growth increased with logging intensity. The growth of C. multiflora was positively correlated to the intensity of the dry season. The different growth strategies of the three species have consequences on the forest management. This work allowed to classify the species studied of Couratari as late secondary species.
Tauari é a denominação popular das madeiras provenientes de várias espécies de Lecythidaceae e estão entre as mais exploradas na Amazônia. A auto-ecologia destas espécies é mal conhecida devido, em parte, ao agrupamento sob o mesmo nome vernacular. Este estudo determina as espécies de tauari ocorrentes nas florestas de terra firme do bioma Amazônia e os seus padrões de abundância e de distribuição geográfica; caracteriza aspectos da regeneração pela morfo-biometria funcional dos frutos e sementes e pela fisiologia da germinação e define as estratégias de crescimento das árvores (DAP>10 cm). Dados de herbários e inventários (>400 ha) no bioma Amazônia foram usados para caracterizar as abundâncias e distribuições geográficas específicas. Descrições morfo-funcionais e medições de frutos e sementes foram feitas a partir de coletas em árvores da Amazônia Central (Manaus e Belterra, Brasil). A morfologia da germinação foi descrita a partir de experimentos em viveiro. A fisiologia da germinação foi analisada a partir de ensaios de tolerância das sementes ao dessecamento, o fotoblastimo e a capacidade de germinar em diferentes temperaturas constantes entre 15 e 35 °C. Estratégias de crescimento foram definidas com base nas taxas de crescimento diamétrico anual (médias e máximas) das árvores durante ~25 anos em florestas exploradas sob diversas intensidades (Paracou, Guiana Francesa; Belterra- PA, Brasil). O nome vernacular tauari agrupa 14 espécies dos gêneros Couratari, Cariniana e Allantoma. Nove foram inventariadas no estudo. Couratari guianensis se destacou por sua maior área de distribuição e alta freqüência nos inventários, porém sempre com abundância baixa (<1 árvore/ha). Cariniana micrantha, Couratari stellata, C. multiflora, C. oblongifolia apresentaram ampla distribuição (>1.10 6 km2), alta freqüência e densidades localmente altas. Couratari atrovinosa, C. longipedicellata e C. tauari mostraram abundâncias baixas e distribuição regional ou restrita. O estudo traz novas informações sobre a carpologia de espécies pouco coletadas (C. atrovinosa, C. tauari, C. longipedicellata) e a primeira descrição do fruto de C. atrovinosa. A biometria apontou a necessidade de uma revisão das seções infragenéricas e/ou das variáveis dos frutos que determinam cada seção para cinco espécies simpátricas da Amazônia Central. A secagem lenta do fruto permite a dispersão gradual das sementes, única entre as Lecythidaceae. As plântulas das cinco espécies de Couratari com os cotilédones foliáceos fotossintetizantes e reservas no hipocótilo constituem um tipo morfo- funcional raro. O hipocótilo, dobrado abaixo da inserção dos cotilédones, era um tipo ainda não documentado. As sementes destas cinco espécies são tolerantes ao dessecamento, pois germinaram com teor de água abaixo de 7,9%. A germinação ocorreu na luz e no escuro. Couratari guianensis e C. stellata apresentavam germinação máxima entre 15 a 35 °C enquanto C. longipedicellata e C. atrovinosa germinaram menos, abaixo de 20 °C e acima de 25 °C. A época de dispersão das sementes (estação seca ou chuvosa) permite separar as espécies. O manejo das sementes e a propagação destas espécies são facilitados pela tolerância ao dessecamento, a germinação rápida, sem necessidade de luz, e a temperatura de 25 °C adequada para avaliação da qualidade das sementes. A estratégia de crescimento definida para C. guianensis, C. multiflora e C. stellata, foi intrínseca da espécie e relacionada à densidade da madeira e tamanho máximo das adultas. Couratari stellata, emergente, teve um potencial de crescimento (PC) fraco no sub-dossel e muito maior acima (DAP 10-19 cm: 4 mm/ano; >30 cm: 16 mm/ano), com altas taxas de crescimento das maiores adultas (DAP>30 cm; 4,6-5,9 cm/ano). Ao contrário, C. multiflora, espécie de dossel inferior, teve um PC negativamente correlato ao tamanho das árvores e o menor crescimento médio para as adultas (DAP>30 cm: 1,8-2,3 mm/ano). O estímulo do crescimento pela exploração durou ~15 anos e foi maior nas áreas mais exploradas. O crescimento de C. multiflora foi positivamente correlato à intensidade da estação seca. As diferentes estratégias de crescimento têm conseqüências sobre o manejo florestal. Este trabalho permitiu classificar as espécies de Couratari estudadas como segundárias tardias na sucessão florestal.
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Heath, Sarah E. "Evolutionary consequences of viral resistance in the marine picoeukaryote Ostreococcus tauri." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31082.
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In marine environments, eukaryotic marine microalgae coexist with the viruses that infect them. Marine microalgae are the main primary producers in the oceans and are at the base of the marine food web. Viruses play important roles in top-down control of algae populations, cycling of organic matter, and as evolutionary drivers of their hosts. Algae must adapt in response to the strong selection pressure that viruses impose for resistance to infection. In addition to biotic selection pressures such as viral infections, algae must also adapt to their abiotic environment. Global climate change is affecting temperature, salinity, pH, light and nutrient concentrations in the oceans, particularly in surface waters, where microalgae live. Currently, little is known about how consistent the effects of viruses on their hosts are, whether the cost of host resistance varies across environments, and whether there is a trade-off between maintaining resistance to viruses and adapting to other environmental changes. The marine picoeukaryote Ostreococcus tauri is abundant in Mediterranean lagoons, where it experiences large fluctuations in environmental conditions and co-occurs with lytic viruses (Ostreococcus tauri viruses – OtVs). Viral infection causes lysis of susceptible (S) cells, however a small proportion of cells are resistant (R) and avoid lysis. Some resistant O. tauri populations can coexist with infectious viruses, and it has been proposed that these viruses are produced by a minority of susceptible cells within a mainly resistant population. These populations are referred to as resistant producers (RP). Virus production in RP populations is unstable and eventually they shift to R populations. I used O. tauri and one of its viruses, OtV5, as a model system to investigate whether cells that are susceptible or resistant to virus infection adapt to environmental change differently and whether there is a cost of being resistant. For the first time, I evolved susceptible and resistant hosts of a marine alga separately under a range of environments and directly compared their plastic and evolved responses. I showed that resistant populations of O. tauri maintained their resistance for more than 200 generations in the absence of viruses across all environments, indicating that the resistance mechanism is difficult to reverse. Furthermore, I did not detect a cost of being resistant, as measured by population growth rate and competitive ability. Virus production in RP populations stopped in all environments and all populations became R. In addition, I found that virus production in RP O. tauri populations can fluctuate before completely ceasing, and that phosphate affected the length of time it took for virus production to stop. These results, combined with mathematical modelling of O. tauri infection dynamics, provide support for the prediction that RP populations consist of a mixed population of susceptible and resistant cells. By examining multiple environments and resistance types, we can better understand first, how microalgae populations adapt to environmental change and second, the ecological and evolutionary consequences of maintaining resistance to viruses in common marine picoeukaryotes.
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Frink, Sabine. "Kinematics of T Tauri stars in nearby star forming regions." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=961689390.
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Daemgen, Sebastian. "The evolution of protoplanetary disks in T Tauri binary systems." Diss., lmu, 2012. http://nbn-resolving.de/urn:nbn:de:bvb:19-149771.
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Stempels, Henricus Cornelis. "An Observational Study of Accretion Processes in T Tauri Stars." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3420.
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Ka'ili, Tēvita O. "Tauhi Vā : creating beauty through the art of sociospatial relations /." Thesis, e-Book (PDF), 2008. http://www.library.auckland.ac.nz.ezproxy.auckland.ac.nz/eproducts/ebooks/Tauhi_Va_Creating_Beauty_Final_Copy.pdf.
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Brannigan, Emma Leigh. "A spectroscopic and spectro-astrometric study of T Tauri stars." Thesis, University of Hertfordshire, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440155.
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Goldsmith, M. J. "A study of R Coronae Borealis and RV Tauri stars." Thesis, Keele University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328254.
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Douglas, Kevin Arthur. "A numerical simulation of the young stellar outflow DG Tauri B." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ56707.pdf.
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Symington, Neil H. "Observations and modelling of accretion phenomena in Classical T Tauri stars." Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421579.
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Machado, Leandro José Rodrigues. "Development and application of stellar wind models to T Tauri stars." Doctoral thesis, Universidade do Porto. Reitoria, 2001. http://hdl.handle.net/10216/9882.
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Jalava, L. (Laura). "Tauti, vaiva vai ominaisuus?:semioottinen tulkinta myöhemmän iän korkean verenpaineen merkityksellistymisestä." Master's thesis, University of Oulu, 2015. http://urn.fi/URN:NBN:fi:oulu-201505141519.
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Korkea verenpaine on yleisimpiä suomalaisten terveyteen liittyviä ongelmia, yksi kansantaudeistamme. Tässä tutkimuksessa tarkastelen korkean verenpaineen merkityksellistymistä sitä sairastavien näkökulmasta. Tutkimusaineistoni ytimen muodostavat kymmenen teemahaastattelua, jotka toteutin vuoden 2013 aikana. Lisäksi aineistoon kuuluu osallistuvaa havainnointia, jossa havainnoinnin kohteena oli sairauteen liittyvä verenpaineen kotiseuranta ja -hoito. Tutkimukseni informanteilla oli todettu iän myötä kohonnut verenpaine, johon ei liittynyt muita sairauksia. Tutkimukseni liikkuu mikrotasolla: siinä, miten aikaan ja paikkaan sidotut yksittäiset henkilöt merkityksellistävät korkeaa verenpainetta.
Tutkimus kuuluu lääketieteellisen antropologian erityisalaan, jonka puitteissa hyödynsin merkityksien tutkimukseen kohdistuvaa teoriaa antropologian ja semiotiikan aloilta. Käsittelin aineistoani narratiiveina, joiden analyysiin sovelsin Clifford Geertzin tulkitsevaa antropologiaa sekä A. J. Greimasin strukturalistista semiotiikkaa. Tutkimuksessani sairaus ei näyttäydy pysyvänä tilana, vaan biologisena ja kulttuurisena merkityksellistymisprosessina. Tätä prosessia avaan tutkimuksessani selvittämällä, mitä korkean verenpaineen merkityksen rakentumiseen vaikuttavia tekijöitä informantit nostavat esiin, ja millaisissa rooleissa ja vuorovaikutussuhteissa nämä tekijät ovat suhteessa informantteihin.
Korkean verenpaineen seuranta ja hoito tapahtui informanttieni tapauksessa pääosin kotona. Tutkimuksen narratiiveista välittyi, että suurin osa informanteista koki itse olevansa vastuussa myös hoidon suhteen tehtävistä päätöksistä. Elämäntapamuutokset hoitomuotona vaativat paljon aikaa ja vaivaa, eikä tuloksista ole takuuta. Lääkkeet puolestaan saattavat aikaansaada hankalaksi koettuja sivuvaikutuksia. Harkittujen ratkaisujen tekeminen edellyttää, että korkeasta verenpaineesta on saatavissa yksilöityä ja monipuolista tietoa. Tässä tutkimuksessa tuotettu tieto auttaa ymmärtämään varsinkin sitä, miten korkea verenpaine näkyy ja merkityksellistyy lääkärinvastaanoton ovien ulkopuolella, jokapäiväisessä arkielämässä.
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Huhtala, H. (Heli). "Tieteellinen tauti, inhimillinen tarina ja yhteinen taistelu:syövän tulkintakehykset ja metaforat journalismissa." Master's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201805241929.
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Tämän pro gradu -työn aihe on syöpäjournalismi suomalaisessa lehdistössä. Tutkielmassa selvitetään, miten syöpää kehystetään ja millaisia metaforia siitä käytetään sekä pohditaan journalismin syövästä antamaa kuvaa. Tutkimuksen aineistona on kuuden lehden syöpää käsittelevät artikkelit (166 kpl) yhden vuoden ajalta. Viestinnän kehysanalyysin apuvälineenä on käytetty Sinikka Torkkolan terveyden ja sairauden kolmen ulottuvuuden mallia (2008) ja Ulla Järven terveysjournalismin lajijaottelua (2011). Metafora-analyysi pohjaa George Lakoffin ja Mark Johnsonin teoriaan metaforista abstraktin ajattelun välineinä. Syöpäjournalismi jakautuu kolmeen pääkehykseen, jotka ovat tiedeusko, potilastarina ja kollektiivinen syöpä. Tiedeusko valaa toivoa syövän parannettavuudesta, kun taas potilastarinat antavat realistisemman kuvan syövän todellisuudesta. Kollektiivisen syövän kehyksessä yksilön ongelmat nostetaan yleiselle tasolle ja yhteisön kohtaamaan syövän uhkaan etsitään ratkaisuja yksilön tasolta.
Kuolema on syöpäjournalismissa kuin kansantarinoiden karhu, jonka oikeaa nimeä ei saa mainita, ettei se vain tule manatuksi esille. Syövän aiheuttama kuoleman uhka kuvataankin suoran ilmaisun sijasta sotametaforilla ja henkilöllistämisellä, jotka korostavat syövän vaarallisuutta sekä valmistavat yhteisöä ja yksilöä taisteluun sitä vastaan. Kokonaisuutena journalismi siis kuvaa syövän vihollisena, jota vastaan taistellaan lääketieteen keinoin ja hoito on matka, jonka päämääränä on paraneminen. Tutkielmassa pohditaan kehysanalyysin tuloksen kautta myös terveysjournalismin tehtäviä. Alan teorioissa toistuu kolmijako, joka oli havaittavissa myös tässä aineistoanalyysissa. Kolmijaon perusteella voidaan terveysjournalismin tehtävinä nähdä sairauden uhan hallinta tieteen avulla, yksilön elämän hallinnan tukeminen ja sairastamisen yhteisvastuullisuuden ylläpito.
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Machado, Leandro José Rodrigues. "Development and application of stellar wind models to T Tauri stars." Tese, Universidade do Porto. Reitoria, 2001. http://hdl.handle.net/10216/9882.
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Kasper, Markus Erdmann. "Optimization of an adaptive optics system and its application to high-resolution imaging spectroscopy of T Tauri." [S.l. : s.n.], 2000. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8986347.
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Williams, Beverley Anne Harwood, and bevwilliams@bigpond com. "The Advent of Methodism and the I Taukei: The Methodist Church in Fijian Nation-making." La Trobe University. School of Social Sciences, Sociology and Anthropology Program, 2008. http://www.lib.latrobe.edu.au./thesis/public/adt-LTU20091221.121517.
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This thesis is an historical anthropology of the role of the Methodist Church in Fiji, from the arrival of Methodist missionaries in 1830. At that time Fiji was a fragmented society. Fijians lived in villages on various islands, so there was no cohesion within the society. The insertion of Methodism into traditional Fijian society irreversibly changed the society, and this thesis traces the key changes that occurred. The rise to prominence of Chief Cakobau from Bau Island marks the beginning of unification of a fragmented Fiji. He formed the first Fijian government in 1871.The British Colonial authorities and the Methodists were also centrally involved in unification and the development of a national society as they set up structures to govern and evangelise the Fijians. However, the thesis argues that with the arrival of Indo-Fijians as indentured labourers to Fiji in 1879, the seeds of polarisation were planted and Indo-Fijians were left out of the frame of Fijian society. The thesis traces the involvement of Methodism, always in close relationship with the state in the twin processes of unification and polarisation.
The coups that have changed the political landscape of Fiji served to alter the relationship between the Methodist Church and the state. A schism occurred in the Methodist Church following the 1987 coup, where violence against some ministers occurred, and the Methodist constitution was suspended. Members belonging to i taukei Methodist hierarchy who insisted on Fijian paramountcy to the exclusion of Indo-Fijians have been separated irretrievably from members of the Methodist hierarchy who believe in an inclusive society irrespective of race. Increasing diversity of socio-economic status allied with hierarchical divides and different interpretations of the Church�s mission have generated conflict in the Church and society at large. Diminution of the power of the Methodist Church in Fiji has occurred since 1987, and there are both internal and external factors at work which continue this trend. The various factors influencing the Church in the present along with its future prospects are discussed.
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Cruz, Gerson Kleber de Almeida. "Variação longitudinal e transversal nas propriedades da madeira do Tauari Vermelho (Cariniana micrantha Ducke – Lecythidaceae)." Universidade Federal do Amazonas, 2006. http://tede.ufam.edu.br/handle/tede/4519.
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FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas
The work had the objective of studying the variation of density, shrinkage and fiber length from pith-bark and base to top direction of the tree. The samples were collected from five equidistant positions in the pith-bark direction, corresponding to 0%, 25%, 50%, 75% and 100%, and in the heights of base, DAP, 50%, 75% and 100% of the tree. Three trees were used and the samples had nominal dimensions of 2,0 x 3,0 x 5,0 cm. The results showed that occurred tendency of basic density variations in pith-bark and base-top directions. In the pith-bark direction the density increased until the position of 50% (heartwood) and followed by decreasing to minimum values on sapwood near bark (100%). Minimum values of density were observed on sapwood and maximum values on heartwood. In the base-top direction, a tendency of decreasing density was observed for samples from sapwood. Minimum values were found on sapwood (100%) where it was practically free of extractives. In the other positions there were not obvious tendencies of density behaviour which may be caused by extractive. Volumetrics and linear shrinkages had tendency to decrease in the pith-bark direction, independently of position of the sample in the trunk. The anisotropic factor (T/R), was lower in the area near pith, increasing substantially towards the sapwood. Area near pith showed smaller rate of anisotropic factor and heartwood and sapwood showed greater rate of anisotropic factor. There was no statistic difference for basic density and volumetric, tangencial and radial shrinkages in the longitudinal direction of the trunk of tauari . But, there was significant statistic differences in the radial direction. The test Tukey of multiple comparisons of averages showed statistic differences on basic density only among the position of 100% and the others. While these were statistically the same to each other, in other words, the density of the heartwood was statistically larger than the density of the sapwood. The same relationship was found in the radial path for tangential and radial shrinkages. Thus, the position of 100%, smaller shrinkage value, was statistically different to the others, with the neighbor's 75% exception. While the shrinkages verified in the positions of 0%, 25%, 50% and 75% did not differ. The results were comparable to the radial volumetric shrinkage. The anisotropic factor, as well as fiber lengths were statistically non significant on both directions (longitudinally and radially).
O trabalho teve por objetivo estudar a variação da densidade, retratibilidade e comprimento de fibras da madeira do tauari vermelho (Cariniana micrantha Ducke – Lecythidaceae), no sentido medula-casca e ao longo da altura da árvore. As amostras foram obtidas em cinco posições eqüidistantes no sentido medula-casca, correspondendo a 0%, 25%, 50%, 75% e 100%, e na Base, DAP, 50%, 75% e 100% da altura comercial da árvore. Três árvores foram usadas e as amostras tiveram dimensões nominais de 2,0 x 3,0 x 5,0 cm. Os resultados mostraram que houve variação da densidade básica no sentido medula-casca. No sentido medula-casca houve uma tendência da densidade aumentar da posição de 50% (cerne) e em seguida diminuir para os valores mínimos na região do alburno próximo a casca (100%). Os mínimos valores de densidade foram verificados na região do alburno e máximos na região do cerne. No sentido basetopo, um comportamento de tendência de decréscimo de densidade foi observado para as amostras retiradas do alburno. Os mínimos valores foram encontrados na região do alburno (100%) o qual está praticamente livre de extrativos. Nas demais posições não houve uma tendência clara de comportamento da densidade, o que pode ser explicado em parte pela presença de extrativos. As contrações volumétricas e lineares totais tenderam a diminuir no sentido medula-casca, independentemente da posição da amostra no fuste. O fator anisotrópico foi mais baixo na região próximo a medula, aumentando em direção a região do alburno. A região próxima a medula apresentou os menores índices de fator anisotrópico e no cerne e alburno os maiores índices. Para a densidade básica e nas contrações (volumétrica, tangencial e radial) não houve diferença estatística no sentido longitudinal do tronco do tauri. Porém, ambos mostraram-se estatisticamente significantes na direção radial. O teste Tukey de comparações múltiplas de média mostrou para a densidade que somente a posição de 100% foi estatisticamente diferente das demais. Enquanto estas foram estatisticamente iguais entre si, ou seja, a densidade do cerne foi estatisticamente maior que a densidade do alburno. A mesma relação foi encontrada no sentido radial para as contrações tangencial e radial. Em que a posição de 100%, menor valor de contração, foi significantemente diferente das demais, exceção da vizinha 75%. Enquanto as contrações verificadas nas posições de 0%, 25%, 50% e 75% não diferiram estatisticamente. Resultados estes são comparáveis à contração volumétrica radial. O fator anisotrópico, assim como comprimento de fibras foram estatisticamente não significativos, tanto no sentido longitudinal como no sentido radial ao tronco do tauari.
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Williams, Beverley. "The advent of Methodism and the I Taukei the Methodist Church in Fijian nation-making /." Bundoora, Victoria : La Trobe University, 2008. http://bibpurl.oclc.org/web/39301.
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Thesis (M.A.) -- La Trobe University, 2008.Description based on print version record. "A thesis in total fulfilment of the requirements for the degree of Master of Arts in Anthropology [to the] School of Social Sciences, Sociology and Anthropology Program, Faculty of Humanities and Social Sciences, La Trobe University, Bundoora". Includes bibliographical references (leaves 151-166)
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Ylönen, S. (Susanna). "Genetic risk factors for movement disorders in Finland." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526223988.
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Abstract Parkinson’s disease and Huntington’s disease are progressive neurodegenerative movement disorders that typically manifest in adulthood. In this study, genetic risk factors contributing to these two movement disorders were investigated in Finnish patients. Patients with early-onset or late-onset Parkinson’s disease as well as population controls were examined. The p.L444P mutation in GBA was found to contribute to the risk of Parkinson’s disease. POLG1 compound heterozygous mutations were detected in two patients with Parkinson’s disease and rare length variants in POLG1 were associated with Parkinson’s disease. Variants in SMPD1, LRRK2 or CHCHD10, previously detected in other populations, were not detected, suggesting that they are rare or even absent in the Finnish population. Patients with Huntington’s disease were investigated for HTT gene haplotypes as well as whether these haplotypes alter the stability of the elongated CAG repeat. Haplogroup A was less common in Finns than in other European populations, whereas it was significantly more common in patients with Huntington’s disease than in the general population. Certain HTT haplotypes as well as the parental gender were found to affect the repeat instability. We found that compound heterozygous mutations in POLG1 were causative of Parkinson’s disease, rare length variants in POLG1 were associated with Parkinson’s disease and GBA p.L444P was significantly more frequent in patients than in the controls, which suggests that these mutations are associated with the development of Parkinson’s disease. The low prevalence of Huntington’s disease in Finland correlates with the low frequency of the disease-associated HTT haplogroup A. Paternal inheritance combined with haplotype A1 increased the risk of repeat expansion. Movement disorders in Finland were found to share some of the same genetic risk factors found in other European populations, but some other recognized genetic variants could not be detectedTiivistelmä Parkinsonin tauti ja Huntingtonin tauti ovat hermostoa rappeuttavia eteneviä liikehäiriösairauksia, jotka tyypillisesti ilmenevät aikuisiällä. Tässä tutkimuksessa selvitettiin näiden kahden liikehäiriösairauden geneettisiä riskitekijöitä suomalaisilla potilailla. Tutkimme potilaita, joilla oli varhain alkava Parkinsonin tauti tai myöhään alkava Parkinsonin tauti sekä väestökontrolleja. GBA-geenin p.L444P mutaation havaittiin lisäävän Parkinsonin taudin riskiä. Kaksi Parkinsonin tautia sairastavaa potilasta oli yhdistelmäheterotsygootteja haitallisten POLG1-geenin varianttien suhteen ja harvinaiset POLG1 CAG toistojaksovariantit assosioituivat Parkinsonin tautiin. Tutkittuja variantteja SMPD1-, LRRK2- ja CHCHD10-geeneissä ei löydetty tästä aineistosta lainkaan, mikä viittaa siihen, että ne puuttuvat suomalaisesta väestöstä tai ovat harvinaisia. Huntingtonin tautia sairastavilta potilailta tutkittiin HTT-geenin haploryhmiä ja niiden vaikutusta Huntingtonin tautia aiheuttavan pidentyneen toistojakson epästabiiliuteen. Haploryhmä A oli suomalaisessa väestössä harvinainen verrattuna eurooppalaiseen väestöön ja se oli huomattavasti yleisempi Huntingtonin tautipotilailla kuin väestössä. Toistojakson epästabiiliuteen vaikuttivat tietyt HTT-geenin haplotyypit samoin kuin sen vanhemman sukupuoli, jolta pidentynyt toistojakso periytyy. POLG1 yhdistelmäheterotsygoottien katsottiin aiheuttavat Parkinsonin tautia ja harvinaisten POLG1 CAG toistojaksovarianttien todettiin assosioituvan Parkinsonin tautiin Suomessa. GBA p.L444P mutaatio merkittävästi yleisempi Parkinsonin tautipotilailla kuin kontrolleilla, mikä viittaa siihen, että se on Parkinsonin taudin riskitekijä. Huntingtonin tautiin assosioituvan haploryhmä A:n matala frekvenssi selittää taudin vähäistä esiintyvyyttä Suomessa. Paternaalinen periytyminen ja haplotyyppi A1 lisäsivät HTT-geenin toistojakson pidentymisen riskiä. Liikehäiriösairauksilla todettiin Suomessa osittain samanlaisia riskitekijöitä kuin muualla Euroopassa, mutta kaikkia tutkittuja variantteja emme havainneet
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Persson, Magnus. "T Tauri stars : Optical lucky imaging polarimetry of HL and XZ Tau." Thesis, Stockholm University, Department of Astronomy, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-35802.
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Optical lucky imaging polarimetry of HL Tau and XZ Tau in the Taurus-Auriga molecular cloud was carried out with the instrument PolCor at the Nordic Optical Telescope (NOT). The results show that in both the V- and R-band HL Tau show centrosymmetric structures of the polarization angle in its northeastern outflow lobe (degree of polarization ~30%). A C-shaped structure is detected which is also present at near-IR wavelengths (Murakawa, 2008), and higher resolution optical images (Stapelfeldt, 1995). The position angle of the outflow is 47.5+-7.5 degrees, which coincides with previous measurements and the core polarization is observed to decrease with wavelength and a few scenarios are reviewed. Measuring the outflow witdh versus distance and wavelength shows that the longer wavelengths scatter deeper within the cavity wall of the outflow. In XZ Tau the binary is partially resolved, it is indicated by an elongated intensity distribution. The polarization of the parental cloud is detected in XZ Tau through the dichroic extinction of starlight. Lucky imaging at the NOT is a great way of increasing the resolution, shifting increases the sharpness by 0.1 asec and selection the sharpest frames can increase the seeing with 0.4 asec, perhaps more during better conditions.
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Fraschetti, F., J. J. Drake, O. Cohen, and C. Garraffo. "Mottled Protoplanetary Disk Ionization by Magnetically Channeled T Tauri Star Energetic Particles." IOP PUBLISHING LTD, 2018. http://hdl.handle.net/10150/627037.
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The evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought to be due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares, or traveling shock waves, and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T. Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesized along the individual particle trajectories. We have investigated the energy range [0.1-10] GeV, consistent with expectations from Chandra X-ray observations of large flares on T. Tauri stars and recent indications by the Herschel Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding a dominance of energetic particles over X-rays in the ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area, except within narrow regions where particles are channeled onto the disk by the strongly tangled and turbulent magnetic field. The radial thickness of such regions is 5 stellar radii close to the star and broadens with increasing radial distance. This likely continues out to large distances from the star (10 au or greater), where particles can be copiously advected and diffused by the turbulent wind.
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Paska, Andrey. "Chemical evolution of inner regions of protoplanetary disks around T Tauri stars." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/chemical-evolution-of-inner-regions-of-protoplanetary-disks-around-t-tauri-stars(86d0948e-1568-4014-9e8b-723244edba5b).html.
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This thesis has investigated the chemical evolution of the inner regions (r ≤ 10 AU) of a modelled protoplanetary disk surrounding a low-mass T Tauri star; a phase our own solar system underwent some 4.5–4.6 billion years ago. A 1+1- dimensional physical model of a radially-accreting protoplanetary disk was combined with a chemical model consisting of gas-phase reactions extracted from the RATE95 UMIST database for Astrochemistry, and to this, a network of gas-grain interaction and deuterated reactions were added. Influenced by the knowledge that radionuclides may have been abnormally abundant in our early solar system compared with the interstellar medium, and that the energy expelled from their decay is sufficient to ionize molecules, a 1-dimensional simulation along the disk midplane was performed, comparing the chemistry with and without radionuclides, as a function of the radionuclide ionization rate. The molecules C4H2, HC3N, C3H, HCN, CH4, C2H2 and N2 were found to be particularly sensitive. Of these, HCN and C2H2 have already been detected in protoplanetary disks. Motivated by observations which suggest that T Tauri systems vary from faster to slower accretion rates, the chemical distributions of two disks with stellar accretion rates of 10−7 M⊙ yr−1 and 10−8 M⊙ yr−1 were compared. Allowing the mass accretion rate (and thus physical conditions) to vary in time, starting from 10−7 M⊙ yr−1, and evolving to a mass accretion rate of 10−8 M⊙ yr−1, the molecules CN, HCN, H2CO and NH3 were found to be particularly sensitive when compared to a standalone 10−8 M⊙ yr−1 simulation. With the use of a 1-D CASA LTE algorithm for ALMA, the sensitivities of HCN and H2CO were transcribed into integrated intensity differences, as a function of emissivity and optical depth. The largest differences were associated with the largest feasible transitions of HCN and H2CO; J = 8-7 and JK = 10010-909 respectively, but could not be converted into potentially observable integrated fluxes due to the restrictions of this model. Both molecules were found to trace different regions of the disk. Using the stellar accretion rate-to-age linear relation evaluated from observations, the calculation times for the 10−7 M⊙ yr−1 and 10−8 M⊙ yr−1 were re-evaluated, of which CN and NH3 emerged as the most sensitive molecules. Thus, CN and NH3 may be a possible tracer of calculation time, and disk age.
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Djouani, Tahri El-batoul. "Caractérisation moléculaire de la transmission lumineuse vers l'horloge circadienne de la microalgue Ostreococcus tauri." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20150.
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Les microalgues du phytoplancton sont exposées à des variations fréquentes et rapides de la qualité et de l'intensité spectrale en milieu marin. On peut donc supposer qu'il existe des mécanismes de photoperception spécifiques aux microalgues, différents de ceux identifiés chez les organismes terrestres. L'importance de l'horloge circadienne dans la transmission de l'information lumineuse et notamment la photopériode a largement été caractérisée chez plusieurs organismes modèles terrestres. Le principal objectif de ma thèse était d'étudier les régulations des gènes de l'horloge en réponse à la lumière, chez la microalgue Ostreococcus tauri. Le développement récent des techniques de génomique fonctionnelle chez cette microalgue eucaryote l'a promue comme un nouvel organisme modèle pour l'étude de mécanismes complexes tels que horloge circadienne. Mon étude s'est focalisée sur la caractérisation d'une voie de signalisation de type système à deux composants susceptible de transmettre le signal lumineux vers l'oscillateur central de l'horloge. J'ai étudié les régulations des principaux acteurs de l'horloge d'Ostreococcus par la lumière, et en particulier celles du gène TOC1. J'ai aussi caractérisé la protéine LOV-HK, un nouveau type de photorécepteur à la lumière bleue chez les eucaryotes, dont l'activité est requise pour le bon fonctionnement de l'horloge d'Ostreococcus. L'importance des régulations transcriptionnelles de TOC1 et de LOV-HK, ainsi que leurs fonctions dans l'oscillateur central ont été abordées par l'utilisation d'un promoteur inductible. Enfin, j'ai montré que LOV-HK et plus globalement l'horloge régulent la croissance cellulaire et la biomasse, démontrant leur rôle central dans le contrôle de la physiologie d'Ostreococcus tauriLight quality and intensity change frequently in the water column. Therefore marine microalgae are exposed to large changes in light spectrum. Photoperception mechanisms in microalgae are expected to differ from those of land plants since the marine environment has unique properties of light transmission. The focus of my PhD project concerns two mains topics, circadian clock regulation and photoperception in the microalga Ostreococcus tauri. In recent years, O. tauri has emerged as a promising model organism using functional genomics approaches to study complex processes such as the circadian clock regulations. My study was focused on the involvement of a two components system in light transmission to the circadian clock of Ostreococcus. I have studied the molecular mechanisms underlying the regulation of the core clock component TOC1. I have also characterized a novel eukaryotic blue light photoreceptor called LOV-HK, which regulates circadian clock function in Ostreococcus. Using an inducible promoter system to modulate the levels of TOC1 and LOV-HK, I have analyzed the importance of their transcriptional regulations in the clock. Finally, I have shown that LOV-HK and more generally the circadian clock, regulates cell growth and biomass in Ostreococcus tauri
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Degraeve, Guilbault Charlotte. "Caractérisation des glycérolipides et de la dynamique de remodelage en chaines acyles chez Ostreococcus tauri." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0825/document.
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La picoalgue verte marine Ostreococcus tauri est un eucaryote minimal développé en système modèle et qui a servi de ressource de gènes en biologie des lipides. Des informations détaillées sur ces caractéristiques lipidiques étaient cependant manquantes. Lors de ma thèse j’ai caractérisé le glycérolipidome d’O. tauri et ai cherché à déterminer quelles sont les cibles enzymatiques responsables de la dynamique des acides gras (FA) et de la régulation du métabolisme lipidique en réponse à des modifications de l’environnement (carences nutritives et refroidissement). O. tauri présente des caractéristiques uniques de composition en lipides et en FA mixtes entre les algues vertes et les Chromalveolates, et a été validé comme espèce modèle pour la classe des Mamiellophyceae. L’acide docosahexaénoïque (DHA) est confiné dans les lipides présumés extraplastidiaux : le phosphatidyldimethylpropanethiol (PDPT) et le bétaïne-lipide diacylglyceryl-hydroxymethyl-trimethyl-β-alanine (DGTA), tous deux marqueurs lipidiques des Chromalveolates. Les lipides plastidiaux de type procaryotique sont caractérisés par une prépondérance de FA polyinsaturés (PUFA) en C18 n-3, le 18:5 n-3 étant restreint aux galactolipides. Le 16:4 n-3, PUFA typique des galactolipides des microalgues vertes, est également un composant majoritaire des lipides extraplastidiaux chez O. tauri. Les triacylglycérols (TAG) présentent tout le panel d’acides gras d’O. tauri et leurs combinaisons moléculaires indiquent une origine plastidiale majoritaire. La carence azote provoque une forte accumulation de TAG, notamment des espèces présentant des combinaisons sn-1/sn-2 en 18:X/16:X et s'accompagne d'un transfert de carbone du phosphatidylglycérol (PG) et du monogalactosyldiacylglycérol (MGDG) aux TAG ce qui indique une contribution croissante de la voie plastidiale à la synthèse des TAG. Des expériences préliminaires de RT-qPCR sur des gènes du métabolisme des TAG révèlent une forte activation transcriptionnelle de certaines diacylglycérol acyltransférases (DAGT). Les carences nutritives répriment sévèrement l’activité Δ6 désaturase, générant une inversion du ratio 18:3/18:4 dans les lipides plastidiaux qui se répercute dans les TAG. La régulation fine et dynamique de ce ratio suggère un rôle important du 18:3 et du 18:4 dans les membranes plastidiales. Le refroidissement engendre une augmentation spécifique du 18:5 des galactolipides. La recherche active de la désaturase responsable de ce phénotype par une approche d'expression de gènes candidats en systèmes homologue et hétérologues (S. cerevisiae, N. Benthamiana) a conduit à l’indentification de deux Δ6 désaturases plastidiales jamais caractérisées dans d'autres systèmes. Celles-ci possèdent des spécificités non redondantes et originales entre elles et par rapport à l'acyl-CoA-Δ6 d'O. tauriThe marine green picoalga Ostreococcus tauri is a minimal eukaryote implemented as model system that has been used as gene resource for lipid biology. Detailed information about its lipidic features was however missing. During my PhD, I characterized O. tauri glycerolipidome and associated dynamics under environmental stresses such as nutrient starvations and chilling and investigated transcriptional variations of putative target enzymes responsible for these changes. O. tauri which could be validated as model for related species of the class Mamiellophyceae, was found to display unique lipidic features related to both green and Chromalveolates microalgae. Docosahexaenoic acid (DHA) is confined to presumed extraplastidial lipids i.e. phosphatidyldimethylpropanethiol (PDPT) and the betaine lipid diacylglyceryl-hydroxymethyl-trimethyl-β-alanine (DGTA); all of these compounds are hallmarks of Chromalveolates. Plastidial lipids found to be of prokaryotic type are characterized by the overwhelming presence of C18 n-3 polyunsaturated FA (PUFA), 18:5 n-3 being restricted to galactolipids. C16:4 n-3, an FA typical of green microalgae galactolipids, also was a major component of O. tauri extraplastidial lipids. Triacylglycerols (TAGs) display the complete panel of FAs, and their molecular combinations designate a major plastidial origin of DAG precursors. Nitrate starvation greatly increases TAG content, in particular 18:X/16:X (sn-1/sn-2) combinations, and was associated with the transfer of carbon from phosphatidylglycerol (PG) and monogalactosyldiacylglycerol (MGDG) to TAG indicating an increased contribution of the plastidial pathway to the TAG synthesis. Preliminary RT-qPCR experiments on TAG metabolism genes revealed an important transcriptional activation of some diacylglycerol acyltransferases (DGAT). Nutrient starvations severely repress Δ6 desaturase activity and result in the inversion of the 18:3/18:4 ratio in plastidial lipids that was feedback into TAG. The fine-tuning and dynamic regulation of the 18:3/18:4 ratio suggests an important physiological role of these FAs in photosynthetic membranes. Chilling generates an increase of 18:5 in galactolipids. The active quest for the desaturases responsible for this phenotype was achieved by expressing candidate genes in homologuous and heterologous (S. cerevisiae, N. Benthamiana) systems and led to the identification of two yet uncharacterized plastidial Δ6 desaturases. These desaturases display original and non-redundant specificity between each other and with the previously characterized in O. tauri Δ6 acyl-CoA desaturase
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Meng, Huan Y. A., Peter Plavchan, George H. Rieke, Ann Marie Cody, Tina Güth, John Stauffer, Kevin Covey, et al. "PHOTO-REVERBERATION MAPPING OF A PROTOPLANETARY ACCRETION DISK AROUND A T TAURI STAR." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621264.
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Theoretical models and spectroscopic observations of newborn stars suggest that protoplantary disks have an inner "wall" at a distance set by the disk interaction with the star. Around T Tauri stars, the size of this disk hole is expected to be on a 0.1 au scale that is unresolved by current adaptive optics imaging, though some model-dependent constraints have been obtained by near-infrared interferometry. Here we report the first measurement of the inner disk wall around a solar-mass young stellar object, YLW 16B in the rho Ophiuchi star-forming region, by detecting the light-travel time of the variable radiation from the stellar surface to the disk. Consistent time lags were detected on two nights, when the time series in H (1.6 mu m) and K (2.2 mu m) bands were synchronized while the 4.5 mu m emission lagged by 74.5 +/- 3.2 s. Considering the nearly edge-on geometry of the disk, the inner rim should be 0.084 au from the protostar on average, with an error of order 0.01 au. This size is likely larger than the range of magnetospheric truncations and consistent with an optically and geometrically thick disk front at the dust sublimation radius at similar to 1500 K. The widths of the cross-correlation functions between the data in different wavebands place possible new constraints on the geometry of the disk.
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Simon, M. N., I. Pascucci, S. Edwards, W. Feng, U. Gorti, D. Hollenbach, E. Rigliaco, and J. T. Keane. "TRACING SLOW WINDS FROM T TAURI STARS VIA LOW-VELOCITY FORBIDDEN LINE EMISSION." IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/622166.
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Using Keck/HIRES spectra (Delta v similar to 7 km s(-1)) we analyze forbidden lines of [O I] 6300 angstrom, [O I] 5577 angstrom. and [S II] 6731 angstrom. from 33 T Tauri stars covering a range of disk evolutionary stages. After removing a high-velocity component (HVC) associated with microjets, we study the properties of the low-velocity component (LVC). The LVC can be attributed to slow disk winds that could be magnetically (magnetohydrodynamic) or thermally (photoevaporative) driven. Both of these winds play an important role in the evolution and dispersal of protoplanetary material. LVC emission is seen in all 30 stars with detected [O. I] but only in two out of eight with detected [S. II], so our analysis is largely based on the properties of the [O. I] LVC. The LVC itself is resolved into broad (BC) and narrow (NC) kinematic components. Both components are found over a wide range of accretion rates and their luminosity is correlated with the accretion luminosity, but the NC is proportionately stronger than the BC in transition disks. The full width at half maximum of both the BC and NC correlates with disk inclination, consistent with Keplerian broadening from radii of 0.05 to 0.5 au and 0.5 to 5 au, respectively. The velocity centroids of the BC suggest formation in an MHD disk wind, with the largest blueshifts found in sources with closer to face-on orientations. The velocity centroids of the NC, however, show no dependence on disk inclination. The origin of this component is less clear and the evidence for photoevaporation is not conclusive.
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Horrobin, Matthew. "A study of T Tauri stars with multiple spectral types and their surface temperatures." Thesis, University of Edinburgh, 2000. http://hdl.handle.net/1842/28248.
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This thesis describes the results of two spectral studies of T Tauri stars. T Tauri stars are young, low mass, stars which have yet to evolve to the point where Hydrogen fusion occurs in their cores. They are normally found in groups associated with gas clouds in locations called star forming regions. Much work has been done to explain the bizarre spectral features of T Tauri stars, and this has led to the development of a standard model for their structures. Classical T Tauri stars are thought to be surrounded by large discs of accreting material, which slowly adds to the mass of the star. This accretion process results in large U.V. and I.R. fluxes for the stars when compared to their main sequence counterparts. Weak-line T Tauri stars do not display any accretion features and are thought to be more evolved than Classical T Tauri stars. Observations show that both types of T Tauri star have active chromospheres and large cool spots, which are both thought to be a result of strong magnetic fields. This thesis is motivated by two studies, one spectroscopic, one photometric, both of which suggest that some T Tauri stars display photospheric features from regions of different temperatures, or multiple spectral types (MST). The first spectral study discussed is of near-I.R. data taken with UKIRT. The spectra are of high resolution data from the region around 1.63 mm, and are of T Tauri, giant and dwarf stars of known spectral type. It is shown that a ratio of selected OH to Fe lines gives a good trend with the optically measured Teff, derived from spectral types, for both dwarfs and giants. Whilst some of the T Tauri stars fit this trend, it is found that 4 stars clearly lie above it. This is taken as an induction of cooler regions in the spectra than had previously been detected, an MST effect. The second spectral study discussed is of optical data taken with the FLAIR system on the UKST. The spectra span the entire optical region observable with this instrument, and are intended to show variation in temperature sensitive features between the blue and red optical regions. Spectra are presented from 2 consecutive nights of observations and previously discovered MST stars are found to show deeper G bands than would be predicted from the TiO bands in the red spectra. It is found that the G band of one object has varied both on a night to night basis and since the previous observations from the mid-1980's. It is also shown that no variation has occurred in the red spectra.
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Herczeg, Gregory J. "Molecular hydrogen fluorescence and accretion in far-ultraviolet spectra of classical T Tauri stars." Diss., Connect to online resource, 2005. http://wwwlib.umi.com/dissertations/fullcit/3178336.
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Pollard, Karen R. "The nature of the low mass supergiants : RV Tauri and R Coronae Borealis variables." Thesis, University of Canterbury. Astronomy, 1994. http://hdl.handle.net/10092/7632.
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A programme of photometric and spectroscopic observations has been undertaken in order to investigate the physical and chemical characteristics of the RV Tauri and R Coronae Borealis variables. These characteristics have, in turn, been used to examine a variety of theoretical models that attempt to describe the pulsation mechanisms, the underlying physical nature and the evolutionary status of these low mass supergiant variables.
Long time baseline BVRI photometry was obtained at the Mt John University Observatory (MJUO) over intervals of between 750 and 1300 days for eleven of the RV Tauri variables. RV Tauri stars from both the RVa (constant mean magnitude) and RVb (varying mean magnitude) photometric subclasses and from all three spectroscopic Preston subtypes (A, B and C types) were included in the programme.
Fourier and least-squares analyses of the light and colour variations have revealed the dominant periodicities and the stability of the pulsation in these stars. A harmonic (f + 2f) fit was found to be a good representation of the "deep-shallow" nature of both the light and colour curves in most stars. Contemporaneous high-resolution spectroscopy of these objects was acquired at MJUO and at the Mt Stromlo Observatory. This enabled us to link the photometric variations and the radial motions in these stars' atmospheres and to relate any photometric and spectral peculiarities. The appearance and phase-dependent behaviour of the Hα line profiles and the radial velocities were examined. Shock-related features, such as line doubling and recombination emission lines, were observed in all the programme stars. The observed Hα profiles were consistent with two enhancements of Hα emission following the passage of the primary and secondary shock waves through the photosphere around phases 0.2 and 0.6. In addition, the metallic lines showed profiles characteristic of an atmospheric shock wave at these phases.
The derived spectroscopic and the photometric characteristics have been used to examine a variety of theoretical models that attempt to describe the pulsation mechanisms and the underlying physical nature of the RV Tauri stars.
The nature of the RVb subclass and the interpretation that the RVa and RVb stars actually represent a continuum of properties is discussed in detail. A model of a binary system which undergoes periodic eclipses by dust or which interacts at certain orbital phases is presented. Two scenarios were proposed to explain the observed properties: an 'obscuration' model where the star is eclipsed by dust in the binary system; or an 'interaction' scenario where the two stars interact in some manner at a particular orbital phase. The interaction model generally has better agreement with the observed properties although it is quite likely, in a system where circumstellar and/or circumbinary material is known to exist, that a combination of obscuration and interaction is possible.
A detailed analysis of the chemical composition of a number of RCB stars in the Galaxy and the Large Magellanic Cloud is presented. This study made use of high-resolution echelle spectra obtained at the Anglo-Australian Telescope. The results for the galactic star, SU Tau, revealed very similar properties to a number of other warm galactic RCB stars, most notably R CrB. This was the first abundance analysis completed for any extragalactic RCB stars and showed a similar abundance distribution to the galactic RCB stars. All these objects (galactic and extragalactic) have a reasonably consistent set of properties, providing evidence that it is possible for this phenomenon to exist in different nucleosynthetic environments.