Organismal tolerance to abiotic environmental stresses contributes significantly to setting the distribution limits of organisms, as demonstrated by vertical zonation patterns in the marine ...intertidal zone. In this thesis, the ultimate (evolutionary) and proximate (mechanistic) causes of tolerance to temperature and emersion stresses associated with the intertidal zone were examined using porcelain crabs, genus Petrolisthes. Species of Petrolisthes from intertidal and subtidal microhabitats of four biogeographic regions of the Eastern Pacific were used in phylogenetically-based comparative analyses of morphological, physiological, and biochemical adaptation to environmental stress. A phylogenetic tree based on the sequence of the 16sRNA gene was developed to facilitate these analyses. Organismal thermal tolerance limits are adapted to match maximal microhabitat temperatures. Acclimation of thermal tolerance limits suggests that temperate intertidal zone species are living close to their thermal maximum in nature. Respiratory responses to emersion vary among species from different vertical zones. Experimental examination of oxygen consumption rates and lactate accumulation during emersion suggests that intertidal species are able to respire in air using thin membranousregions on the ventral meral segments of their legs (leg membranes). Leg membrane sizeis positively correlated with body size across species, but not within a single species. Evolutionary analyses indicate that leg membranes may not have evolved for purposes of aerial respiration, but their presence may have allowed intertidal and subtidal species to achieve larger body sizes and higher metabolic rates. The thermal stabilities of an enzyme, lactate dehydrogenase (LDH), from 22 species of Petrolisthes varied widely, butwere not correlated with maximal habitat temperatures. Comparative analyses did not indicate any evolutionary relationship between LDH thermal stability and microhabitat conditions. Experimental evidence suggests that interspecific differences in LDH stability are genetically based, and are due both to intrinsic properties of the LDH molecules and extrinsic protein stabilizers. Elucidation of the mechanism(s) of LDH stabilization in Petrolisthes may provide novel insight to the field of protein stabilization. These results studies suggest that individual traits may be subjected to differing levels of selection, and thus the analysis of environmental adaptation requires careful consideration of the biological significance of the traits being examined.
We report the results of our spectrophotometric monitoring campaign for AT~2017be in NGC~2537. Its lightcurve reveals a fast rise to an optical maximum, followed by a plateau lasting about 30 days, ...and finally a fast decline. Its absolute peak magnitude (\(M_{r}\) \(\simeq\) \(-\)12 \(\rm{mag}\)) is fainter than that of core-collapse supernovae, and is consistent with those of supernova impostors and other Intermediate-Luminosity Optical Transients. The quasi-bolometric lightcurve peaks at \(\sim\) 2 \(\times\) 10\(^{40}\) erg s\(^{-1}\), and the late-time photometry allows us to constrain an ejected \(^{56}\)Ni mass of \(\sim\) 8 \(\times\) 10\(^{-4}\)\msun. The spectra of AT~2017be show minor evolution over the observational period, a relatively blue continuum showing at early phases, which becomes redder with time. A prominent H\(\alpha\) emission line always dominates over other Balmer lines. Weak Fe {\sc ii} features, Ca~{\sc ii} H\(\&\)K and the Ca {\sc ii} NIR triplet are also visible, while P-Cygni absorption troughs are found in a high resolution spectrum. In addition, the Ca~{\sc ii} \(\lambda\)7291,7324 doublet is visible in all spectra. This feature is typical of Intermediate-Luminosity Red Transients (ILRTs), similar to SN~2008S. The relatively shallow archival Spitzer data are not particularly constraining. On the other hand, a non-detection in deeper near-infrared HST images disfavours a massive Luminous Blue Variable eruption as the origin for AT~2017be. As has been suggested for other ILRTs, we propose that AT~2017be is a candidate for a weak electron-capture supernova explosion of a super-asymptotic giant branch star, still embedded in a thick dusty envelope.
(Abridged) X1822-371 is the prototypical accretion disc corona X-ray source, a low-mass X-ray binary viewed at very high inclination, thereby allowing the disc structure and extended disc coronal ...regions to be visible. We study the structure of the accretion disc in X1822-371 by modelling the phase-resolved spectra both in optical and X-ray regime. We analyse high time resolution optical ESO/VLT spectra of X1822-371 to study the variability in the emission line profiles. In addition, we use data from XMM-Newton space observatory to study phase-resolved as well as high resolution X-ray spectra. We apply the Doppler tomography technique to reconstruct a map of the optical emission distribution in the system. We fit multi-component models to the X-ray spectra. We find that our results from both the optical and X-ray analysis can be explained with a model where the accretion disc has a thick rim in the region where the accretion stream impacts the disc. The behaviour of the H_beta line complex implies that some of the accreting matter creates an outburst around the accretion stream impact location and that the resulting outflow of matter moves both away from the accretion disc and towards the centre of the disc. Such behaviour can be explained by an almost isotropic outflow of matter from the accretion stream impact region. The optical emission lines of HeII 4686 and 5411 show double peaked profiles, typical for an accretion disc at high inclination. However, their velocities are slower than expected for an accretion disc in a system like X1822-371. This, combined with the fact that the HeII emission lines do not get eclipsed during the partial eclipse in the continuum, suggests that the line emission does not originate in the orbital plane and is more likely to come from above the accretion disc, for example the accretion disc wind.
We present ultraviolet, optical and infrared photometry and optical spectroscopy of the type Ic superluminous supernova (SLSN) Gaia16apd (= SN 2016eay), covering its evolution from 26 d before the ...\(g\)-band peak to 234.1 d after the peak. Gaia16apd was followed as a part of the NOT Unbiased Transient Survey (NUTS). It is one of the closest SLSNe known (\(z = 0.102\pm0.001\)), with detailed optical and ultraviolet (UV) observations covering the peak. Gaia16apd is a spectroscopically typical type Ic SLSN, exhibiting the characteristic blue early spectra with O II absorption, and reaches a peak \(M_{g} = -21.8 \pm 0.1\) mag. However, photometrically it exhibits an evolution intermediate between the fast- and slowly-declining type Ic SLSNe, with an early evolution closer to the fast-declining events. Together with LSQ12dlf, another SLSN with similar properties, it demonstrates a possible continuum between fast- and slowly-declining events. It is unusually UV-bright even for a SLSN, reaching a non-\(K\)-corrected \(M_{uvm2} \simeq -23.3\) mag, the only other type Ic SLSN with similar UV brightness being SN 2010gx. Assuming that Gaia16apd was powered by magnetar spin-down, we derive a period of \(P = 1.9\pm0.2\) ms and a magnetic field of \(B = 1.9\pm0.2 \times 10^{14}\) G for the magnetar. The estimated ejecta mass is between 8 and 16 \(\mathrm{M}_{\odot}\) and the kinetic energy between 1.3 and \(2.5 \times 10^{52}\) erg, depending on opacity and assuming that the entire ejecta is swept up into a thin shell. Despite the early photometric differences, the spectra at late times are similar to slowly-declining type Ic SLSNe, implying that the two subclasses originate from similar progenitors.
Master files scanned at 600 ppi (256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9080C in TIF format. PDF derivative scanned at 300 ppi (256 B&W, 256 Grayscale), using Capture Perfect 3.0, on ...a Canon DR-9080C. CVista PdfCompressor 3.1 was used for pdf compression and textual OCR.
The influence of large-scale processes on natural communities has become one of the central issues of modern ecology. I combined field and laboratory studies to investigate the effects of variation in coastal upwelling on rocky intertidal communities along the central Oregon coast. I examined whether the growth of intertidal barnacles (Balanus glandula and Chthamalus dalli) at two sites was linked to nearshore phytoplankton abundance. Short-term growth rates were low during a persistent upwelling event and increased two to three-fold during the subsequent relaxation of upwelling. Although this increase coincided with a large phytoplankton bloom at one site, parallel increases in growth occurred at a second site where no bloom was recorded. Published analyses of barnacle stomach contents suggest that zooplankton may be an important component of barnacle diets. Barnacle growth may thus be enhanced during upwelling relaxations through the combined benefits of more phytoplankton, more zooplankton, and warmer water temperatures. In laboratory studies, I tested the hypothesis that upwelling-related variation in water temperature regulates the feeding, growth, and energetics of two intertidal predators, the sea star Pisaster ochraceus and whelk Nucella canaliculata. Sea stars and whelks maintained at 9°C generally consumed 30% fewer mussels than those at 12°C. Animals that were exposed to cyclic temperatures (alternating between 12°C and 9°C every two weeks) tended to grow faster than those held at constant temperatures. Consumers in upwelling systems may thus feed intensely during periods of warmer water while benefiting from reduced metabolic costs during cold-water intrusions. I conducted field experiments to quantify the effect of small changes in water temperature on the interaction between a keystone predator, Pisaster ochraceus, and the intertidal mussel Mytilus californianus. Per capita and per population effects of sea stars on transplanted mussels were sharply reduced during a persistent cold-water upwellingevent. Interannual variation in the frequency and intensity of upwelling may thus altercommunity dynamics through effects on this keystone interaction. Taken together, these studies suggest that upwelling-related variation in nearshore conditions can profoundly influence intertidal systems at the organismal, population, and community level.
El tumor de Wilms o nefroblastoma es una neoplasia renal que se origina debido a alteraciones en la embriogénesis renal; se presenta sobre todo en edad pediátrica (solo el 3% corresponde a casos en ...adultos) y tiene un componente genético importante, pues se asocia a síndromes como el de Denys-Drash, el de Perlman y el de Beckwith-Wiedemann. Su manifestación clínica inicial suele ser una masa abdominal (detectada casi siempre en estadios avanzados de la enfermedad) acompañada de hematuria intermitente; además, es posible que debute comprometiendo órganos cercanos. El tratamiento debe ser multimodal y con un enfoque multidisciplinario, sus pilares son: cirugía, quimioterapia y radioterapia, cuya pertinencia y secuencia se determinan según la estadificación realizada de acuerdo con los protocolos internacionales de las asociaciones pediátricas referentes: el Children’s Oncology Group (COG) y la International Society of Pediatric Oncology (SIOP). A continuación se reporta un caso de tumor de Wilms en un paciente adulto, así como la descripción de sus características clínicas y paraclínicas, el abordaje quirúrgico llevado a cabo, los estudios patológicos realizados y los esquemas de quimioterapia y radioterapia elegidos.
We present results from the final six months of a survey to search for pulsations in white dwarfs and hot subdwarf stars with the Kepler spacecraft. Spectroscopic observations are used to separate ...the objects into accurate classes, and we explore the physical parameters of the subdwarf B (sdB) stars and white dwarfs in the sample. From the Kepler photometry and our spectroscopic data, we find that the sample contains 5 new pulsators of the V1093 Her type, one AM CVn type cataclysmic variable, and a number of other binary systems. This completes the survey for compact pulsators with Kepler. No V361 Hya type of short-period pulsating sdB stars were found in this half, leaving us with a total of one single multiperiodic V361 Hya and 13 V1093 Her pulsators for the full survey. Except for the sdB pulsators, no other clearly pulsating hot subdwarfs or white dwarfs were found, although a few low-amplitude candidates still remain. The most interesting targets discovered in this survey will be observed throughout the remainder of the Kepler Mission, providing the most long-term photometric datasets ever made on such compact, evolved stars. Asteroseismic investigations of these datasets will be invaluable in revealing the interior structure of these stars, and will boost our understanding of their evolutionary history.
Physiological studies can help predict effects of climate change through determining which species currently live closest to their upper thermal tolerance limits, which physiological systems set ...these limits, and how species differ in acclimatization capacities for modifying their thermal tolerances. Reductionist studies at the molecular level can contribute to this analysis by revealing how much change in sequence is needed to adapt proteins to warmer temperatures--thus providing insights into potential rates of adaptive evolution--and determining how the contents of genomes--protein-coding genes and gene regulatory mechanisms--influence capacities for adapting to acute and long-term increases in temperature. Studies of congeneric invertebrates from thermally stressful rocky intertidal habitats have shown that warm-adapted congeners are most susceptible to local extinctions because their acute upper thermal limits (LT(50) values) lie near current thermal maxima and their abilities to increase thermal tolerance through acclimation are limited. Collapse of cardiac function may underlie acute and longer-term thermal limits. Local extinctions from heat death may be offset by in-migration of genetically warm-adapted conspecifics from mid-latitude 'hot spots', where midday low tides in summer select for heat tolerance. A single amino acid replacement is sufficient to adapt a protein to a new thermal range. More challenging to adaptive evolution are lesions in genomes of stenotherms like Antarctic marine ectotherms, which have lost protein-coding genes and gene regulatory mechanisms needed for coping with rising temperature. These extreme stenotherms, along with warm-adapted eurytherms living near their thermal limits, may be the major 'losers' from climate change.
Nova V458 Vul erupted on 2007 August 8th and reached a visual magnitude of 8.1 a few days later. H\(\alpha\) images obtained six weeks before the outburst as part of the IPHAS galactic plane survey ...reveal an 18th magnitude progenitor surrounded by an extended nebula. Subsequent images and spectroscopy of the nebula reveal an inner nebular knot increasing rapidly in brightness due to flash ionization by the nova event. We derive a distance of 13 kpc based on light travel time considerations, which is supported by two other distance estimation methods. The nebula has an ionized mass of 0.2 M\(_{\odot}\) and a low expansion velocity: this rules it out as ejecta from a previous nova eruption, and is consistent with it being a ~14,000 year old planetary nebula, probably the product of a prior common envelope (CE) phase of evolution of the binary system. The large derived distance means that the mass of the erupting WD component of the binary is high. We identify two possible evolutionary scenarios, in at least one of which the system is massive enough to produce a Type Ia supernova on merging.
Global change includes alterations in ocean temperature, oxygen availability, salinity, and pH, abiotic variables with strong and interacting influences on the physiology of all taxa. Physiological ...stresses resulting from changes in these four variables may cause broad biogeographic shifts as well as localized changes in distribution in mosaic habitats. To elucidate these causal linkages, I address the following questions: What types of physiological limitations can alter species' distributions and, in cases of extreme stress, cause extinctions? Which species are most threatened by these physiological challenges--and why? How do contents of genomes establish capacities to respond to global change, notably in the case of species that have evolved in highly stable habitats? How fully can phenotypic acclimatization offset abiotic stress? Can physiological measurements, including new molecular ("-omic") approaches, provide indices of the degree of sublethal stress an organism experiences? And can physiological evolution keep pace with global change?
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