Factors Governing Patterns Of Brood Defense In Male Smallmouth Bass (micropterus Dolomieui)

I examined the effects of offspring stage, brood size, and parental age on the patterns of brood defense in nesting male smallmouth bass (Micropterus dolomieui), a centrarchid fish with male parental care, in Lake Opeongo, Ontario. Parental defense against conspecific models of equal length ((+OR-)1 cm) was used as a measure of parental commitment to the brood. Based on Williams\u27 principle, or the trade-off between present and future reproduction, parental males should adjust their level of brood defense to reflect the value of current offspring relative to their expected future reproduction.;Parental defense increased as a model intruder approached the nest and as offspring progressed from egg to hatched embryo stages (wrigglers), and peaked prior to \u27swim-up\u27 of fry from the nest. This pattern of brood defense over a nest cycle demonstrates the changing value of present offspring relative to the parent\u27s expected future reproduction within a season.;In response to manipulating brood size, parental males increased their defense for augmented broods and decreased their defense for reduced broods, relative to a control. This demonstrates that parental males can adjust their level of brood defense to reflect future prospects of reproductive success.;Long-term data on population estimates and tagged nesting males in Lake Opeongo provided the necessary life history information to predict patterns of parental defense based on the reproductive value of males. Reproductive value at the age of first nesting for males in different age groups was partitioned into current reproduction (wrigglers in the nest) and to future reproduction (residual reproductive value). This index indicated that young nesting males (age 4, 5, and 6) should be more aggressive than older males (age 8+). The prediction was not supported; older males were more aggressive than young males. This discrepancy can be interpreted as either reduced reproductive effort in young males or increased effort in older males because of possibly larger resource budgets. The life history of this population suggests that size-based energetic constraints are important in determining patterns of brood defense between different age classes

Properties of the CO and H2_2O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observations

Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is well suited for studying the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims. We intend to investigate the shape and composition of the close molecular layer (also known as the MOLsphere) that surrounds the star. This analysis is part of a wider program that aims at understanding the dynamics of the circumstellar envelope of Betelgeuse. Methods. On January and February 2011, Betelgeuse was observed using the Astronomical Multi-BEam combineR (AMBER) instrument of the Very Large Telescope Interferometer (VLTI) in the H and K bands. Using the medium spectral resolution of the instrument (R $\sim$ 1500), we were able to investigate the carbon monoxide band heads and the water-vapor bands. We used two different approaches to analyse our data: a model fit in both the continuum and absorption lines and then a fit with a Radiative HydroDynamics (RHD) simulation. Results. Using the continuum data, we derive a uniform disk diameter of $41.01 \pm 0.41$~mas, a power law type limb-darkened disk diameter of $42.28 \pm 0.43$~mas and a limb-darkening exponent of $0.155 \pm 0.009$. Within the absorption lines, using a single layer model, we obtain parameters of the MOLsphere. Using a RHD simulation, we unveil the convection pattern in the visibilities. Conclusions. We derived a new value of the angular diameter of Betelgeuse in the K band continuum. Our observations in the absorption lines are well reproduced by a molecular layer at 1.2 stellar radii containing both CO and H$_2$O. The visibilities at higher spatial frequencies are matching a convection pattern in a RHD simulation.Comment: 13 pages, 11 figures, accepted for publication in Astronomy & Astrophysics; Language editin

Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. Principle

Using 2 aspheric mirrors, it is possible to apodize a telescope beam without losing light or angular resolution: the output beam is produced by ``remapping'' the entrance beam to produce the desired light intensity distribution in a new pupil. We present the Phase-Induced Amplitude Apodization Coronagraph (PIAAC) concept, which uses this technique, and we show that it allows efficient direct imaging of extrasolar terrestrial planets with a small-size telescope in space. The suitability of the PIAAC for exoplanet imaging is due to a unique combination of achromaticity, small inner working angle (about 1.5 $\lambda/d$), high throughput, high angular resolution and large field of view. 3D geometrical raytracing is used to investigate the off-axis aberrations of PIAAC configurations, and show that a field of view of more than 100 $\lambda/d$ in radius is available thanks to the correcting optics of the PIAAC. Angular diameter of the star and tip-tilt errors can be compensated for by slightly increasing the size of the occulting mask in the focal plane, with minimal impact on the system performance. Earth-size planets at 10 pc can be detected in less than 30s with a 4m telescope. Wavefront quality requirements are similar to classical techniques.Comment: 35 pages, 16 figures, Accepted for publication in Ap

An edge-on translucent dust disk around the nearest AGB star L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 microns and VLTI interferometry

As the nearest known AGB star (d=64pc) and one of the brightest (mK-2), L2 Pup is a particularly interesting benchmark object to monitor the final stages of stellar evolution. We report new lucky imaging observations of this star with the VLT/NACO adaptive optics system in twelve narrow band filters covering the 1.0-4.0 microns wavelength range. These diffraction limited images reveal an extended circumstellar dust lane in front of the star, that exhibits a high opacity in the J band and becomes translucent in the H and K bands. In the L band, extended thermal emission from the dust is detected. We reproduce these observations using Monte-Carlo radiative transfer modeling of a dust disk with the RADMC-3D code. We also present new interferometric observations with the VLTI/VINCI and MIDI instruments. We measure in the K band an upper limit to the limb-darkened angular diameter of theta_LD = 17.9 +/- 1.6 mas, converting to a maximum linear radius of R = 123 +/- 14 Rsun. Considering the geometry of the extended K band emission in the NACO images, this upper limit is probably close to the actual angular diameter of the star. The position of L2 Pup in the Herzsprung-Russell diagram indicates that this star has a mass around 2 Msun and is probably experiencing an early stage of the asymptotic giant branch. We do not detect any stellar companion of L2 Pup in our adaptive optics and interferometric observations, and we attribute its apparent astrometric wobble in the Hipparcos data to variable lighting effects on its circumstellar material. We however do not exclude the presence of a binary companion, as the large loop structure extending to more than 10 AU to the North-East of the disk in our L band images may be the result of interaction between the stellar wind of L2 Pup and a hidden secondary object. The geometric configuration that we propose, with a large dust disk seen almost edge-on, appears particularly favorable to test and develop our understanding of the formation of bipolar nebulae.Comment: 16 pages, 15 figure

Investigation into the role of Aurora A kinase activity during mitosis

Aurora A is an important mitotic regulator that has been found to be up-regulated in a variety oftumours provoking a great deal of attention and the development of a number of small moleculeAurora kinase inhibitors. Most of these inhibitors though have predominantly targeted Aurora B,meaning that our understanding of the role of the kinase activity of Aurora A is comparatively lesswell developed.MLN8054 however, is a small molecule inhibitor that has been reported in vitro to have a highdegree of specificity towards Aurora A activity. In this thesis, I show in vivo that MLN8054 can beused to specifically inhibit Aurora A activity, and exploit this quality to probe the role of Aurora Aactivity in human cells. I was consequently able to show that Aurora A activity not only has a clearrole in spindle formation, where it is required for the determination of K-fibre length and in thedegree of centrosome separation, but also in the regulation of microtubule organisation. Despite thespindle deformities seen after inhibiting Aurora A activity, the majority of HeLa and DLD-1 cellswere still able to form bipolar spindles capable of attaching to kinetochores. These spindlestructures did not however, assert normal levels of force through the kinetochores, and cells wereconsequently unable to efficiently align their chromosomes, causing significant delays to mitoticprogression. Cells were still able to divide in the absence of Aurora A activity, although thedetection of segregation defects and aneuploid progeny indicates a role for Aurora A activity in thefaithful segregation of the genetic material. Importantly however, Aurora A activity was not foundto have a prominent role in the spindle assembly checkpoint.Increasing the potency of Aurora A inhibition by using a drug-resistant cell line confirmed theobservations made in HeLa and DLD-1 cells, emphasising that although Aurora A activity isrequired for spindle assembly, cells can still activate the spindle checkpoint and divide in itsabsence. I therefore propose that Aurora A activity is required for the formation of normal spindlestructures capable of efficiently aligning and evenly dividing chromosomes during cell division.These roles were attributed in part to the kinase activity of Aurora A in the regulation of TACC3and chTOG localisation on the spindle and centrosomes.Interestingly however, Aurora A activity did not appear to be required for spindle assembly in nontransformedcells, which were able to more efficiently align their chromosomes and dividefollowing Aurora A inhibition than the cancer cell lines. Furthermore, the non-transformed cellsaccumulated with 2N DNA after longer-term Aurora A inhibition, as opposed to the cancer celllines, which exhibited profound aneuploidy following the equivalent treatment. This finding isencouraging, as consistent with recently published reports, it indicates that Aurora A inhibitionmay be successfully used in order to specifically target cancer cells.EThOS - Electronic Theses Online ServiceGBUnited Kingdo