Дисертації з теми "Chamaeleon"

The dependence of the mass accretion rate on the stellar properties is a key constraint for star formation and disk evolution studies. Here we present a study of a sample of stars in the Chamaeleon I star-forming region carried out using spectra taken with the ESO VLT/X-shooter spectrograph. The sample is nearly complete down to stellar masses (M-star) similar to 0.1 M-circle dot for the young stars still harboring a disk in this region. We derive the stellar and accretion parameters using a self-consistent method to fit the broadband flux-calibrated medium resolution spectrum. The correlation between accretion luminosity to stellar luminosity, and of mass accretion rate to stellar mass in the logarithmic plane yields slopes of 1.9 +/- 0.1 and 2.3 +/- 0.3, respectively. These slopes and the accretion rates are consistent with previous results in various star-forming regions and with different theoretical frameworks. However, we find that a broken power-law fit, with a steeper slope for stellar luminosity lower than similar to 0.45 L-circle dot and for stellar masses lower than similar to 0.3 M-circle dot is slightly preferred according to different statistical tests, but the single power-law model is not excluded. The steeper relation for lower mass stars can be interpreted as a faster evolution in the past for accretion in disks around these objects, or as different accretion regimes in different stellar mass ranges. Finally, we find two regions on the mass accretion versus stellar mass plane that are empty of objects: one region at high mass accretion rates and low stellar masses, which is related to the steeper dependence of the two parameters we derived. The second region is located just above the observational limits imposed by chromospheric emission, at M-star similar to 0.3-0.4 M-circle dot. These are typical masses where photoevaporation is known to be effective. The mass accretion rates of this region are similar to 10(-10) M-circle dot/yr, which is compatible with the value expected for photoevaporation to rapidly dissipate the inner disk.

The mass of a protoplanetary disk limits the formation and future growth of any planet. Masses of protoplanetary disks are usually calculated from measurements of the dust continuum emission by assuming an interstellar gas-to-dust ratio. To investigate the utility of CO as an alternate probe of disk mass, we use ALMA to survey (CO)-C-13 and (CO)-O-18 J = 3-2 line emission from a sample of 93 protoplanetary disks around stars and brown dwarfs with masses from 0.03 to 2 M-circle dot in the nearby Chamaeleon I star-forming region. We detect (CO)-C-13 emission from 17 sources and (CO)-O-18 from only one source. Gas masses for disks are then estimated by comparing the CO line luminosities to results from published disk models that include CO freeze-out and isotope-selective photodissociation. Under the assumption of a typical interstellar medium CO-to-H-2 ratio of 10(-4), the resulting gas masses are implausibly low, with an average gas mass of similar to 0.05M(Jup) as inferred from the average flux of stacked (CO)-C-13 lines. The low gas masses and gas-to-dust ratios for Cha I disks are both consistent with similar results from disks in the Lupus star-forming region. The faint CO line emission may instead be explained if disks have much higher gas masses, but freeze-out of CO or complex C-bearing molecules is underestimated in disk models. The conversion of CO flux to CO gas mass also suffers from uncertainties in disk structures, which could affect gas temperatures. CO emission lines will only be a good tracer of the disk mass when models for C and CO depletion are confirmed to be accurate.

Recent investigations of the colour excess distribution towards the geometric center of the Chamaeleon-Musca dark clouds complex and the Southern Coalsack dark cloud have suggested that, although being apart by more than 15, these clouds might be physically associated. In order to sustain such hypothesis a new photometric programme has been carried out to trace the extinction between the features. We used the Str¨omgren Automatic Telescope at the European Southern Observatory (ESO), in La Silla (Chile), to obtain uvby_ photometry for all stars, earlier than G0 in the catalog of the Smithsonian Astronomical Observatory, covering the area defined by the Galactic coordinates 308 l 294 and 20 b 5. The programme has resulted on very precise uvby_ data for 1017 stars. Analysis of the colour excess E(by) vs. distance diagrams for these stars has indicated the presence of a local low absorption volume limited at 150 ?30 pc from the Sun by an extended interstellar dust sheet-like structure, that is followed by a region where almost no additional reddening is measured for another 350 pc. The existence of such absorbing feature, at a distance identical to the molecular clouds, has suggested that Coalsack, Chamaeleon and Musca might be dense condensations embbeded in the diffuse medium composing the feature. Furthermore, the minimum column density of the absorbing structure seemed to increase with the Galactic latitude, but without clear dependence on the Galactic longitude. Such effect suggested either an inhomogeneous sheet-like structure, that could be perpendicular to the Galactic plane, or a sheet-like structure of same minimum column density, curved away from the Sun. When viewed in connection to the other data on the local ISM, the existence of these two low-reddening volumes has led to the idea that the dust sheet could be part of a large scale structure, probably related to the interface of the Local and Loop I Bubbles. To investigate the local interstellar medium (ISM) components towards the Southern Coalsack and Chamaeleon-Musca dark clouds we have used the 1.4m Coud´e Auxiliary Telescope at ESO to obtain high-resolution (R 60 000) spectra of the interstellar NaI D absorption lines towards 64 B-type stars (d 500 pc) selected to cover these clouds. The radial velocities, column densities, velocity dispersions, colour excess and distances to the stars have been used to understand the kinematics and distribution of the interstellar cloud components. The analysis indicates that the interstellar gas is distributed in two extended sheet-like structures permeating the whole area, one at d 60 pc and another, that corresponds to the dust sheet observed photometrically, around 120-150 pc from the Sun. The nearby feature is approaching the Sun with average radial velocity of -7 kms1, has low average column density logNNa i 11.2 cm2 and is subject to supersonic turbulent motion as indicated by the velocity dispersion b 5 kms1. The more distant feature has column densities between 12.3 logNNa i 13.2 cm2, average velocity dispersion b 2.5 kms1. Its velocity is centered around 0 kms1, but there is a trend for increasing from -3 kms1 near b = 1 to 3 kms1 near b = 18. The nearby low column density feature indicates a general outflow from the Sco-Cen association, in aggreement with several independent lines of data in the general searched direction. From the radial velocities point of view, the component around 120 150 pc has column densities that suggest neutral gas associated to the dust sheet-like feature observed towards the studied clouds. The fact that the velocities observed in this work (4 km s1 VLSR +3 km s1) are also observed in adjacent directions, supposedly related to the interface of the Local and Loop I bubbles, suggest that Coalsack, Chamaeleon and Musca seem to be part of such interaction zone.
Investigações recentes da distribuição dos excessos de cor na direção do centro geométrico do complexo de nuvens Chamaeleon-Musca e da nuvem escura Saco de Carvão sugeriram que, apesar de estarem separadas por mais de 15o no céu, estas nuvens poderiam estar fisicamente associadas. Para se comprovar tal hipótese um novo programa fotométrico foi realizado, utilizando-se o telescópio dinamarquês de 50 cm instalado no European Southern Observatory (ESO), em La Silla (Chile). Foram selecionadas todas as estrelas dos tipos espectrais anteriores a G0 do catálogo do Smithsonian Astronomical Observatory (SAO) cobrindo a área definida pelas coordenadas Galácticas: 294o  l 307o, 20o  b 5o, que contém as nuvens em questão. Este novo programa resultou em um total de 1017 estrelas com dados uvby de excelente qualidade. A análise dos vários diagramas de excesso de cor E(b-y) por distncia indica que existe um volume local de baixa densidade, limitado por uma extensa estrutura de poeira interestelar que dista cerca de 150 ±30 pc do Sol, e é seguida por uma segunda região onde pouco avermelhamento é detectado por 350 pc. A presença dessa estrutura de poeira interestelar, à mesma distncia das nuvens estudadas, sugere que as nuvens Saco de Carvão, Chamaeleon e Musca (SCCM) podem ser regiões de maior densidade embebidas em uma estrutura de grande escala, provavelmente relacionada com a interface entre as Bolhas Local e Loop I. Além disso a distribuição do avermelhamento indica que o excesso de cor mínimo E(b-y)min, causado pela estrutura de poeira, apesar de não apresentar uma dependência com a longitude Galáctica, parece aumentar com a latitude Galáctica. Tal aumento sugere que a lâmina pode não ser homogênea, estando quase que perpendicular ao plano Galáctico, ou que a lâmina tem uma mesma coluna de densidade mínima, mas está curvada na direção oposta ao Sol. Para se investigar a cinemática das componentes do meio interestelar local na direção das nuvens SCCM, foi realizado um programa espectroscópico, visando a obtenção de espectros de alta resolução (R ~ 60 000) das linhas de absorção interestelar do doubleto de sódio neutro. Utilizando-se o telescópio CAT (Coudé Auxiliary Telescope) de 1.4m, também instalado no ESO, foram observadas 64 estrelas do tipo espectral B localizadas até 500 pc do Sol, e cujos valores de excesso de cor e distância foram precisamente determinados na investigação fotométrica acima. A análise das componentes do gás interestelar na direção das nuvens SCCM indica que o material está distribuído em duas estruturas tipo-lâmina, que se estendem por toda a área estudada. Uma delas está situada a distâncias menores do que 60 pc, enquanto a outra, correspondendo à lâmina de poeira observada fotometricamente, está localizada em torno de 120 a 150 pc do Sol. A componente mais próxima tem baixa coluna de densidade (log NNa ~ H11.2 cm-1 ), está se aproximando do Sol, em relação ao padrão local de repouso (LSR), a uma velocidade média VLSR~ 7 km s-1, e está sujeita a movimentos supersônicos turbulentos, como indicado pelo paraocirc;metro de dispersão de velocidades b ~ 5 km s-1. Já a estrutura mais distante tem coluna de densidade entre 12.3 log NNa  13.2 cm-2 e tem menor dispersão de velocidades b ~ 2.5 km s-1. A sua velocidade está centrada em torno de 0 km s-1, em relação ao LSR, mas existe uma tendência de aumento desde -3 km s-1 em torno do plano Galáctico para +3 km s-1 pr´oximo à latitude Galáctica b = -18o. A estrutura de menor coluna de densidade é consistente com outras observações de um fluxo de matéria vindo da direção da associação Sco-Cen. Do ponto de vista das velocidades radiais, a componente densa em torno de 120 - 150 pc tem coluna de densidade que sugere gás neutro associado com a lâmina de poeira observada na direção das nuvens SCCM. O fato de que as velocidades observadas neste trabalho (-4 km s-1  VLSR +3 km s-1) são também observadas em direções adjacentes, supostamente relacionadas com a interface entre as bolhas Local e Loop I, sugere que a lâmina densa de poeira e gás também faz parte da zona de interação entre as bolhas.

Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de Agronomia
In 2013, a new Ophelimus sp. was detected in a Eucalyptus arboretum in Lisbon. This study aims to study the bio-ecological characteristics of Ophelimus sp. as basic knowledge for its management. We further compare it with the previous introduced species Ophelimus maskelli. Our results showed morphological differences on the galls and adults of O. maskelli and Ophelimus sp., and on the host species. Eucalyptus globulus and E. viminalis were the most susceptible species to Ophelimus sp., whereas it was confirmed a preference of O. maskelli for E. camaldulensis, E. rudis and E. tereticornis. Intraspecific differences regarding gall size and infestation levels of Ophelimus sp. within E. globulus were further registered. Ophelimus sp. has one generation per year and about 30% of larvae and pre-adult mortality was registered due to unknown factors. These traits will contribute to a slower growth rate of its populations when compared to those of O. maskelli. In the North of Portugal, Ophelimus sp. seems to be better adapted, as indicated by the higher population levels compared to those observed in the South. From our surveys, we did not find galls with Closterocerus chamaeleon or any other parasitoid that could allow for the biocontrol of Ophelimus sp.

While substrate-borne vibrations are utilized by different reptile species, true conspecific communication via biotremors has not yet been demonstrated in reptiles. This study follows a preliminary report that the veiled chameleon (Chamaeleo calyptratus) could produce biotremors in communicative contexts. I tested chameleon behavioral sensitivity to vibrations by placing them on a dowel attached to a shaker emitting vibrations of 25, 50, 150, 300, and 600 Hz and then measured their changes in velocity before and after the stimulus. I then paired chameleons in various social contexts [anthropogenic disturbance (human disruption of animal); dominance (malemale; female-female C. calyptratus); courtship (male-female C. calyptratus); heterospecific (C. calyptratus + C. gracilis); and predator-prey (adult + juvenile C. calyptratus)] and used a video camera and accelerometers to record their behavior. This study demonstrates that chameleons produce biotremors and that receivers exhibit a freeze response when exposed to a simulated biotremor stimulus. Furthermore, veiled chameleons produce biotremors in anthropogenic disturbance, conspecific dominance and courtship contexts, and these biotremors are elicited by visual contact with another adult conspecific and heterospecifics. Overall, two classes of biotremor were identified, "hoots” and “rumbles,” which differ significantly in dominant frequency and waveform. No correlation was identified between animal size and dominant frequency of the biotremors they produced as biotremors originate from rapid muscle contractions. Juvenile chameleons of two months of age are able to produce biotremors, suggesting this behavior may have multiple functions. Overall, the data suggest that the veiled chameleon has the potential to utilize substrate-borne vibrational communication during conspecific and possibly heterospecific interactions.

Vibratory communication has evolved in numerous animal groups, including insects, spiders, fishes, mammals, and was recently discovered in veiled chameleons (Chamaeleo calyptratus). I examined the mechanism by which C. calyptratus produce these biotremors. Muscle activity data were gathered during simulated anti-predator responses via electromyography (EMG) with simultaneous recordings of biotremor production using an accelerometer. I correlated EMG data with the accelerometer data to implicate the muscles responsible for the production of the biotremors. Mixed-effect linear regression models described the mechanism, and a model selection framework determined which model fit the data best. I then used an analysis of variance to partition the variance to each variable to determine which muscles were most important in the biotremor producing mechanism. The Mm. sternohyoideus superficialis et profundus, Mm. mandibulohyoideus, and M. levator scapulae were active during the production of biotremors. Mean latency calculations revealed that the M. levator scapulae and Mm. mandibulohyoideus activated prior to the vibration onset, and the Mm. sternohyoideus superficialis et profundus activated after the vibration onset. The M. sternohyoideus superficialis then ceased activity prior to vibration cessation, and the M. sternohyoideus profundus, Mm. mandibulohyoideus, and M. levator scapulae ceased activity after the vibration had ended. The description of the biotremor producing mechanism further supports that C. calyptratus can produce biotremors, possibly for communication.

El camaleó vetllat (Chamaeleo calyptratus) i el camaleó pantera (Furcifer pardalis) són dues de les espècies de camaleó més populars al món, i en conseqüència, dues de les que més freqüentment s’atenen a les consultes veterinàries. Les diferents tècniques de diagnòstic per imatge solen incloure’s de forma rutinària als protocols diagnòstics en medicina herpetològica com són la radiografia, la ecografia, la tomografia computeritzada y la ressonància magnètica. Tot i així, els estudis publicats sobre descripció anatòmica mitjançant tècniques d’imatge són escassos, i la interpretació d’aquestes últimes es basa en l’experiència pròpia del clínic o bé per extrapolació d’altres espècies prèviament estudiades. Per aquest motiu, els objectius d’aquest estudi anatòmic prospectiu van ser desenvolupar protocols de diagnòstic per imatge en aquestes espècies i descriure l’anatomia dels òrgans de la cavitat celòmica en animals sans, mitjançant l’ús de la radiografia, l’ecografia i la tomografia computeritzada. Es van incloure disset camaleons vetllats (7 mascles i 10 femelles) i quinze camaleons pantera (13 mascles i 2 femelles) sans en base als resultats de l’examen físic general i de l’estudi corològic. L’estudi es va realitzar en camaleons sedats mitjançant l’administració d’alfaxalona (Alfaxan®, Crawley, UK) 4-6 mg/kg IV a la vena ventral de la cua. Un cop sedats, es va realitzar un estudi radiogràfic amb dues projeccions (lateral dreta i dorsoventral) amb xassís de mamografia. Seguidament, es va realitzar un estudi ecogràfic complet de la cavitat celòmica amb l’ús de sonda lineal de 15 a 18-MHz en decúbit lateral dret. Finalment, es va realitzar una tomografia computeritzada helicoidal amb un escàner de 16 talls en decúbit esternal. Es va realitzar l’estudi postmortem d’un exemplar de cada espècie per tal d’aclarir, il·lustrar i avaluar les troballes de les proves d’imatge. Els resultats obtinguts suggereixen que les diferents tècniques d’imatge estudiades permeten la visualització del fetge (incloent la vena cava caudal i las venes hepàtiques), la vesícula biliar, l’estómac, els intestins, les gònades, els cossos grassos i els ronyons en camaleons vetllats i pantera. La bufeta de la orina només es va identificar mitjançant ecografia i tomografia. La melsa, el pàncrees i les glàndules adrenals van ser identificades als estudis postmortem però no van poder visualitzar-se mitjançant cap tècnica d’imatge. En conclusió, aquest estudi proporciona una guia de les característiques anatòmiques normals dels òrgans celòmics mitjançant tècniques de diagnòstic per imatge en camaleons vetllats i camaleons pantera. D’aquesta manera, les troballes poden ser utilitzades com a referència durant els exàmens de pacients malalts o per a futurs estudis d’investigació.
El camaleón velado (Chamaeleo calyptratus) y el camaleón pantera (Furcifer pardalis) son dos de las especies de camaleón más populares en el mundo, y en consecuencia, dos de las que más frecuentemente se atienden en la consulta veterinaria. Las diferentes técnicas de diagnóstico por imagen suelen incluirse de forma rutinaria en los protocolos diagnósticos en medicina herpetológica, entre ellas la radiografía, la ecografía, la tomografía computerizada y la resonancia magnética. Sin embargo, los estudios publicados sobre descripción anatómica mediante técnicas de imagen son escasos, y la interpretación de estas últimas se basa en la experiencia propia del clínico o bien por extrapolación de otras especies ya estudiadas. Por este motivo, los objetivos de este estudio anatómico prospectivo fueron desarrollar protocolos de diagnóstico por imagen en estas especies y describir la anatomía de los órganos de la cavidad celómica en animales sanos, mediante el uso de radiografía, ecografía y tomografía computerizada. Se incluyeron diecisiete camaleones velados (7 machos y 10 hembras) y quince camaleones pantera (13 machos y 2 hembras) sanos en base a los resultados del examen físico general y del estudio coprológico. El estudio se realizó en camaleones sedados tras la administración de alfaxalona (Alfaxan®, Crawley, UK) 4-6 mg/kg IV en la vena ventral de la cola. Una vez sedados, se realizó un estudio radiográfico con dos proyecciones (lateral derecha y dorsoventral) con chasis de mamografía. Seguidamente, se realizó un estudio ecográfico completo de la cavidad celómica mediante sonda lineal de 15 a 18-MHz en decúbito lateral derecho. Finalmente, se realizó una tomografía computerizada helicoidal con un scanner de 16 cortes en decúbito esternal. Se realizó el estudio post mortem de un ejemplar de cada especie por tal de esclarecer, ilustrar y evaluar los hallazgos de imagen. Los resultados obtenidos sugieren que las diferentes técnicas de imagen estudiadas permiten la visualización del hígado (incluyendo la vena cava caudal y las venas hepáticas), la vesícula biliar, el estómago, los intestinos, las gónadas, los cuerpos grasos y los riñones en camaleones velados y pantera. La vejiga de la orina solo pudo identificarse mediante ecografía y tomografía. El bazo, el páncreas y las glándulas adrenales fueron identificados en los estudios post mortem pero no pudieron ser visualizados mediante ninguna de las técnicas de imagen. En conclusión, este estudio proporciona una guía de las características anatómicas normales de los órganos celómicos mediante técnicas de diagnóstico por imagen en camaleones velados y camaleones pantera. De esta forma, los hallazgos pueden ser utilizados como referencia para exámenes de pacientes enfermos o para futuros estudios de investigación.
Veiled chameleon (Chamaeleo calyptratus) and Panther chameleon (Furcifer pardalis) are the most popular chameleons over the world, and consequently, two of the most frequently species attended in veterinary practice. The most commonly used imaging techniques in diagnostic protocols in herpetology include radiography, ultrasonography (US), computed tomography (CT) and magnetic resonance imaging (MRI). However, few studies about imaging description in reptiles have been published. The objectives of this prospective anatomic study were to develop imaging techniques for these species and to describe the normal anatomy of the coelomic organs using radiography, US and CT scan. Seventeen healthy veiled chameleons (7 males and 10 females) and fifteen healthy panther chameleons (13 males and 2 females) were included in the study. Animals were considered to be healthy on the basis of the results of a complete physical examination and coprology testing. The imaging study was performed in sedated chameleons after the administration of alfaxalone (Alfaxan®, Crawley, UK) 4-6 mg/kg IV in the ventral vein of the tail. A right lateral and dorsoventral radiographic views were performed with a mammography cassette plate in all animals. Then, an ultrasound was performed in right lateral recumbency using a linear 15 to 18-MHz transducer. Finally, a CT examination was performed with a 16-slice helical CT scanner in sternal recumbency. Post-mortem study of one chameleon of each species were used to clarify and illustrate coelomic anatomy and to assess imaging findings. The results of the current study suggest that the different imaging techniques (radiography, ultrasonography and computed tomography) allow the visualization of the liver (including caudal vena cava and hepatic veins), gallbladder, stomach, intestines, gonads, fat bodies and kidneys in healthy veiled and panther chameleons. The urinary bladder was identified using US and CT examination. The spleen, pancreas and adrenal glands were identified in post-mortem studies, but could not be visualized with any imaging technique. In conclusion, this study provides a guide of the normal imaging anatomic features of the coelomic organs in veiled chameleons and panther chameleons. Findings can be used as a reference for future research studies or for examinations of clinically ill patients.

Tese de mestrado em Biologia da Conservação, apresentada à Universidade de Lisboa, através da Faculdade de Ciências, 2017
O objectivo dos centros de recuperação de animais selvagens é tratar e devolver à Natureza animais feridos, doentes ou órfãos. Contudo, geralmente não se sabe o que acontece aos animais recuperados após a devolução ao seu habitat natural. Esta situação torna-se particularmente problemática quando se trata de espécies ameaçadas ou sobre as quais se desconhece os seus movimentos e requisitos ambientais. O camaleão-comum ( Chamaeleo chamaeleon ) é um réptil que, em Portugal, se distribui exclusivamente pelo litoral algarvio, onde as suas populações têm vindo a sofrer com o aumento da urbanização e do turismo. O RIAS é o único centro de recuperação de animais selvagens no Algarve, recebendo por ano uma média de 30 indivíduos desta espécie. Apesar de o camaleão-comum ser uma espécie emblemática desta região e de existirem vários estudos sobre a sua biologia, ainda permanecem desconhecidos alguns dados referentes à sua área vital e capacidade de dispersão. De forma a compreender o estado da população local, bem como quais os habitats preferenciais, realizou-se previamente um censo de camaleão-comum na área de estudo – a Quinta de Marim, Olhão. Os movimentos de 9 camaleões foram monitorizados com recurso a telemetria, 3 residentes e 6 recuperados no RIAS. Observou-se que camaleões residentes têm preferência por zonas de transição entre sapal e ambiente terrestre, enquanto que os indivíduos introduzidos percorreram vários habitats dentro da Quinta de Marim. Os camaleões introduzidos apresentaram áreas vitais muito superiores às dos residentes, o que corresponde a comportamentos anteriormente observados aquando da introdução de outras espécies em zonas desconhecidas. Apesar das movimentações algo erráticas, os camaleões libertados nunca abandonaram a área de estudo, o que poderá indicar que o procedimento de devolução à Natureza de camaleão-comum no RIAS é executado com sucesso.
The main objective of wildlife rehabilitation centers is to heal and then release back to Nature wounded, ill or orphan wild animals. However, in most cases it is not known what happens to rehabilitated animals when returned to their natural habitats. This is a particularly problematic situation when it concerns endangered species or when there is little information about its movements and environmental requirements. The common chameleon ( Chamaeleo chamaeleon ) is a reptile which, in Portugal, is distributed exclusively along the Algarve coast, where its populations have been impacted with the increasing urbanization and tourism in this region. RIAS is the only wildlife rehabilitation center in Algarve and the main common chameleon receiver, with an average of 30 admissions per year. Even though the common chameleon is an emblematic species of this region and several studies regarding its biology had already been done, there is little information about its vital areas and dispersion capacity. In order to understand the status of the local population, as well as which are the preferred habitats, a common chameleon census was conducted in the study area – Quinta de Marim, Olhão. The movements of 9 chameleons were monitored using telemetry: 3 residents and 6 recovered at RIAS. Resident chameleons have a preference for transition zones between marshland and terrestrial habitats, while introduced individuals wandered through several habitats within Quinta de Marim. Introduced chameleons presented vital areas far superior to the resident ones, which corresponds to behaviors previously observed when introducing other species in unknown areas. Despite the somewhat erratic movements, the released chameleons never left the study area, which may indicate that RIAS’ reintroduction procedure of common chameleon is executed successfully.

The deep southern sky surrounding the Chamaeleon dark clouds is abundant with pre-main sequence stars of various ages. Because of their youth (5-10 Myr) and proximity (d~100 pc), members of the open cluster Eta Chamaeleontis and the nearby Epsilon Chamaeleontis Association are ideal laboratories to study the formation and evolution of extrasolar planetary systems. To better understand their role as potential planet hosts, this thesis explores the formation, dynamical evolution, accretion and disk properties of both groups' low-mass members. The notable lack of low-mass stars in the young open cluster Eta Cha has long been puzzling. Two possible explanations have been suggested; a top-heavy initial mass function or dynamical evolution, which preferentially ejected the low-mass members. Previous efforts to find these stars several degrees from the cluster core have been unsuccessful. By undertaking a wider (95 sq deg) photometric and proper motion survey with extensive follow-up spectroscopy, we have identified eight low-mass stars that were ejected from Eta Cha over the past 5-10 Myr. Comparison with recent simulations shows our results are consistent with a dynamical origin for the current configuration of the cluster, without the need to invoke an initial mass function deficient in low-mass objects. Two of the dispersed members exhibited strong, variable H-alpha emission during our observations, including a star which had an event suggestive of accretion from a circumstellar disk. New infrared photometry confirms the presence of the disk. This star demonstrates that infrequent, episodic accretion can continue at low levels long after most disks around `old' pre-main sequence stars have dissipated. Another two confirmed non-members are slightly older than the cluster, but are only 42 arcseconds apart and share similar kinematics and distances. We show that they almost certainly form a wide (4000-6000 AU) ~10 Myr-old binary at 100-150 pc. The system is one of the widest pre-main sequence binaries known. Its isolation and dynamical fragility put strong constraints on any birthplace and mode of formation, which we propose was in a turbulent gas filament in the vicinity of the Scorpius-Centaurus OB Association. In addition to Eta Cha, we have also examined membership of the unbound Epsilon Chamaeleontis Association, which lies some 10 degrees to the east and has a similar age, distance and kinematics. The two groups were almost certainly born in the outer regions of Sco-Cen only a few million years apart. Many members of Epsilon Cha have been proposed in the decade since its discovery. After considering the kinematics of candidates from the literature, we have confirmed 11 further stars as likely members. Many new members possess infrared spectral energy distributions attributable to circumstellar disks, including four stars with strong H-alpha and forbidden emission which are actively accreting material. Our work on Eta and Epsilon Chamaeleontis has identified many interesting targets for follow-up studies of disk evolution, accretion, binarity, and other investigations that require samples of nearby pre-main sequence stars. Several avenues for future work are discussed, including the impact of photometry and astrometry from the forthcoming SkyMapper Southern Sky Survey.

碩士
國立臺北教育大學
藝術與造形設計學系碩士班
107
This thesis is titled “the Chamaeleon in the Spectrum of Photography” as I use chamaeleon to symbolise my works – they are in disguise in the realm of photography, appearing to be similar but actually not alike in terms of methodologies and presentation. A spectrum consists of a gradation of successive changes – not like black and white in binary oppositions – and there is no sharp division between them but gradations of successive changes. The “artificial nature” in my works fights with two different characters in the spectrum and turns to be impressive in the dialectics of images. Its multiple characters make it hard to be defined and categorised. The thesis consists of three main chapters. Chapter 1: Artificial nature. I used the Picnic series as a way to explore this concept: Is it possible for the representation of nature and the manmade installations in the environment to successfully transfer our emotion for nature elsewhere? I took shots of decorative scenes in specific areas in Taiwan with alienated perspectives, imposing a sense of conflict through the composition I made. The decoration in the rooms were like scenes on the stage, and I used them to start a visual narrative. During the process, I once had the desks and chairs re-arranged for compositional purpose, which prompted me to think about the difference between documentary and staged photography. Chapter 2: Alternative photography. The Ghost Park features animal sculptures. I made use of light to create dramatic scenes without including people in the images. I made the photos seem like being arranged while they actually stay on the grounds between that of documentary and conceptual photography so that I can explore the in-between possibilities. Based on traditional photography, I developed “light painting” techniques that involved a torch to light up the scenes, through which I created a magical moment that was real but also fictional, inviting the audience to connect with the scenes and then get alienated with them. In my experimenting with light painting, I started to ponder upon the essence of photography and decided to turn to the ideas of anti-photography in the next series. Chapter 3: Anti-traditional-photography. In the noise series, I reflected the techniques in the Ghost Park and wondered if it is possible to generate images without light and pinholes? In response to light painting, the techniques derived from traditional photography, I did not introduce light to this series. From feelings to reason, between digital and film, I tried to explore the extremity of digital photography and created noise images from the current that went through the image sensor. These glitches images became my raw materials to create star-photography-like images. Chapter 4: Conclusion. My works impose a strong force of tension against the two different characters intentionally. I aimed to break through the boundaries of techniques and visual effects that relate to traditional photography. These three series of works inspired me to think about the characters of the mediums; therefore, I will continue to experiment with the possibilities of mediums in the future.

In this thesis, we focus on obtaining and interpreting observational information on (i) the role of multiplicity on the properties of young stars; (ii) the early evolutionary influence of circumstellar disks; and (iii) the nature of accretion in young systems. To facilitate this research, we conducted an extensive multi-epoch high-resolution spectroscopic survey at optical wavelengths (3,200-10,000 A) of ~200 T Tauri stars in the ~2 Myr old Chamaeleon I, and Taurus-Auriga star-forming regions with the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan Clay 6.5 m telescope. From the spectroscopic data, we identify eight close binaries and four close triples, of which three and two, respectively, are new discoveries. We find that the multiplicity fraction for Cha I and Tau-Aur are similar to each other, and to the results of field star surveys. The frequency of systems with close companions in our sample is not seen to depend on primary mass or accretion. We probed for evidence of disk braking. We did not see a statistically significant difference between the distribution of rotational velocities with the presence of an inner disk. Also, our findings show that F-K stars in our sample have larger rotational velocities and specific angular momentum than M stars. We also analyzed accretion variability in our sample using the H\alpha 10% width and the CaII-8662 line flux as accretion diagnostics. We find that the maximum extent of accretion variability in our sample was reached on timescale of a few days, indicating that rotation could significantly contribute to the variability.

The Trapezium Cluster stellar population is studied in detail using near-infrared and optical means in order to probe the clustered mode of low and high mass star formation. We determine fundamental stellar parameters such as the spectral types, ages, masses, extinctions and dust excesses for a significant number of cluster stars. Various techniques are applied to deredden the stars in the color-magnitude diagram and hence compare intrinsic positions with theoretical evolutionary tracks. Through these means, we estimate properties of the low mass stellar population to greater accuracy than has previously been achieved. Near-infrared photometry of Trapezium Cluster stars provides an initial evaluation of the nature of the cluster population. This evaluation is improved upon using optical spectroscopy to measure spectral types of a large number of Trapezium Cluster stars for the first time. We find our sample of Trapezium Cluster stars to have a mean spectral type of mid-K, in agreement with :findings for the low mass stars in the vicinity of, and external to, the central cluster. The stars are dereddened on the color-magnitude diagram using our acquired spectral types. Their intrinsic positions provide the most accurate determination for the cluster age obtained to date, -10/6 yr, confirming the pre-main sequence nature of the population. This age estimate is extended to the infrared cluster population of more than 550 stars revealed by infrared-array images. The K luminosity function for the infrared cluster is used in combination with the cluster age to derive the stellar mass distribution. The slope of the mass function obtained here is found to be comparable with the slopes of field initial mass functions. A mean stellar mass of, -0.9 Mo is estimated for the low mass stars. Our determinations for the masses, ages, and spectral types of Trapezium Cluster stars shows that they are a similar stellar population to the more extended Orion Nebula Cluster population, except in density of stars. The mass density of the Trapezium system of low mass and high mass (01 Ori) stars is found to be -4690 Mo pc-3 , approximately 1.5 times greater than previous estimates based on optical studies. The stellar mass derived for the low mass cluster is also used to calculate the star formation efficiency in the region to first order, -72%. This is similar to, but higher than, the star formation efficiencies determined in other regions of embedded cluster formation. The mean extinction estimated for the low mass cluster stars in our sample place the stars at approximately the same depth into the molecular cloud as the Trapezium OB stars, at the near-face of the cloud. Our sample is biased towards optical members of the cluster, suggesting that a significant number of the low mass stars may be embedded more deeply in the molecular cloud than the OB stars. However, using the K luminosity function for the infrared cluster we determine that the low mass cluster is most probably not spread through the whole cloud, but is pre-dominantly located close to the near-face of the cloud. Dust excess determinations show that the Trapezium Cluster stars sampled here contain a typical proportion of classical (dust-excess) T Tauri stars compared with naked (no dust-excess) T Tauri stars for a young stellar population. Approximately one-third of our sample have insignificant dust excesses. Calcium II IR triplet emission is observed in members of our Trapezium Cluster sample. We judge that the strengths of the triplet features imply a circumstellar disk origin for the emission. The frequency of calcium triplet emitting stars is estimated for our sample. We compare this estimate with the proportion of triplet emitters in a sample of Chamaeleon pre-main sequence stars. We find that 20-30 % of classical T Tauri stars in the two populations exhibit triplet emission; the frequency of triplet emission in the Trapezium Cluster sample is found to be comparable with that in Chamaeleon. We perform an approximate dynamical analysis of the Trapezium Cluster star-forming region using our estimates for stellar mass and age. The low mass cluster is found to be at an early stage in its dynamical evolution, and has not had time to completely relax as a system and lose its initial characteristics. It is too young, therefore, to exhibit mass segregation, and the observed isothermality of the stars is proposed here to arise from the distribution of the clumps from which the stars have formed. The high mass stars considered separately are determined to be old enough to have relaxed as a system. We find that, if the 01 Ori stars are located centrally with respect to the low mass cluster, then they are most likely to have formed in their present locations rather than have arrived there from larger radii through dynamical friction processes. In addition, the binding energies of the two high mass binary systems are found to be almost forty times the energy of the low mass cluster. It is suggested that the binary energies must have been acquired through their formation processes instead of through dynamical interactions with the low mass cluster. Thus, present characteristics of the stellar population of the Trapezium Cluster directly relate to the conditions under which the cluster formed, and are not due to dynamical processes among the stars themselves. The total stellar mass determined for the low mass cluster is estimated to be sufficient to bind the cluster at this time. This remains true even with future removal of gas from the region. However, continued dynamical interactions may lead to the eventual dissipation of the low mass cluster.

This study investigates the etiology, diagnosis, and treatment of follicular stasis in female veiled chameleons (Chamaeleo calyptratus). Reproductive status was assessed by enzyme immunoassay of fecal metabolites of estrogen, progesterone, testosterone, and corticosterone; ultrasonography; and male introduction trials. Ultrasonography and hormone pattern analysis confirmed follicular stasis, while female response to male presence was inconclusive. Hormone patterns of corticosterone metabolites indicated a cyclical pattern consistent with reproductive events, but there was insufficient data to compare peak levels between ovulatory and non-ovulatory cycles. Ovulation induction was unsuccessful using either chicken GnRH-II, or a combination of progesterone and prostaglandin F2α. Feed restriction induced weight loss, but this was not directly related to changes in follicle size. Prevention of follicular development (i.e. contraception) was attempted using Depo-Provera and Lupron Depot, but neither treatment was effective. The outcomes of this study supplement the information on follicular stasis in reptiles, but further research is still needed.
NSERC, Toronto Zoo

Thesis (M.Tech.: Homoeopathy)-Dept of Homoeopathy, Durban University of Technology, 2007 xiii, 315 leaves
This study was conducted by administering Chamaeleo dilepis dilepis 30CH to healthy individuals with the aim of eliciting and documenting the resulting mental, emotional and physical symptomology. Chamaeleo dilepis dilepis was chosen as a substance based on it being indigenous to South Africa and as no other members of the Chamaeleonidae species have been proven

Thesis (M.Tech.: Homoeopathy)-Dept. of Homoeopathy, Durban University of Technology, 2007 xiv, 348 leaves
The purpose of this investigation was to determine the effect of Chamaeleo dilepis dilepis on healthy volunteers (provers), and to record the signs and symptoms produced, so that it may be prescribed to those suffering from similar symptoms as determined by the Law of Similars. A further aim of the investigation was to compare the materia medica of Chamaleo dilepis dilepis as determined by proving symptoms to those remedies yielding the highest numerical value and total number of rubrics on repertorisation of the proving symptoms of Chamaeleo dilepis dilepis.