The discovery of the nest of the Colima Warbler (Vermivora crissalis)

http://deepblue.lib.umich.edu/bitstream/2027.42/56278/4/MP033.pd

The birds of Brewster County, Texas.

http://deepblue.lib.umich.edu/bitstream/2027.42/56282/4/MP037.pd

The sub-millimetre evolution of V4334 Sgr (Sakurai's Object)

We report the results of monitoring of V4334 Sgr (Sakurai's Object) at 450 microns and 850 microns with SCUBA on the James Clerk Maxwell Telescope. The flux density at both wavelengths has increased dramatically since 2001, and is consistent with continued cooling of the dust shell in which Sakurai's Object is still enshrouded, and which still dominates the near-infrared emission. Assuming that the dust shell is optically thin at sub-millimetre wavelengths and optically thick in the near-infrared, the sub-millimetre data imply a mass-loss rate during 2003 of ~3.4(+/0.2)E-5 for a gas-to-dust ratio of 75. This is consistent with the evidence from 1-5micron observations that the mass-loss is steadily increasing.Comment: 5 pages, 4 eps figures, accepted for publication in MNRA

Cohesin regulates VSG monoallelic expression in trypanosomes

Antigenic variation allows Trypanosoma brucei to evade the host immune response by switching the expression of 1 out of ∼15 telomeric variant surface glycoprotein (VSG) expression sites (ESs). VSG ES transcription is mediated by RNA polymerase I in a discrete nuclear site named the ES body (ESB). However, nothing is known about how the monoallelic VSG ES transcriptional state is maintained over generations. In this study, we show that during S and G2 phases and early mitosis, the active VSG ES locus remains associated with the single ESB and exhibits a delay in the separation of sister chromatids relative to control loci. This delay is dependent on the cohesin complex, as partial knockdown of cohesin subunits resulted in premature separation of sister chromatids of the active VSG ES. Cohesin depletion also prompted transcriptional switching from the active to previously inactive VSG ESs. Thus, in addition to maintaining sister chromatid cohesion during mitosis, the cohesin complex plays an essential role in the correct epigenetic inheritance of the active transcriptional VSG ES state

Identification and Characterization of Novel Drug Resistance Loci in Plasmodium falciparum

Malaria has plagued mankind for millennia. Antimalarial drug use over the last century has generated highly drug-resistant parasites, which amplify the burden of this disease and pose a serious obstacle to control efforts. This dissertation is motivated by the simple fact that malaria parasites have become resistant to nearly every antimalarial drug that has ever been used, yet the precise genetic mechanisms of parasite drug resistance remain largely unknown. Our work pairs genomics-age technologies with molecular biology, genetics and molecular epidemiology in order to identify and characterize novel genes that contribute to drug resistance in P. falciparum. In the Introduction, we highlight relevant opportunities and challenges in trying to identify and understand the genetic basis of malaria drug resistance as it emerges to currently used therapies. In Chapter One, we demonstrate how genome-wide association studies (GWAS) can be applied to P. falciparum in order to identify novel drug resistance loci. Functional follow-up revealed that overexpression of the novel candidate gene PF10_0355 made parasites more resistant to the drugs halofantrine, lumefantrine and mefloquine. These findings show that PF10_0355 plays a role in parasite drug response, as well as provides validation of our GWAS approach. In Chapter Two, we further characterize PF10_0355 and show that modulation of the gene by either knockout or allelic replacement changes parasite drug sensitivity. Furthermore, we show that moderate changes in drug response measured in the short-term can have dramatic effects when parasites are competed with one another under drug pressure. In Chapter Three, we use an overexpression approach to functionally follow up other novel drug resistance genes generated by GWAS in P. falciparum. We find that overexpression is a useful way to begin to screen candidate drug resistance loci in the malaria parasite. In Chapter Four, we use a DAPI-based ex vivo drug assay to monitor drug resistance among parasites circulating in Thiés, Senegal. In the future, we will look for genetic markers of parasite drug resistance in this population by GWAS. Finally, in the Discussion we present an essay about malaria evolution and eradication written for non-specialists. Our hope is that the work presented in this dissertation furthers understanding of drug resistance in the malaria parasite, both within and beyond the malaria research community

Sakurai's Object: characterizing the near-infrared CO ejecta between 2003 and 2007

We present observations of Sakurai's Object obtained at 1–5 μm between 2003 and 2007. By fitting a radiative transfer model to an echelle spectrum of CO fundamental absorption features around 4.7 μm, we determine the excitation conditions in the line-forming region. We find 12C/13C = 3.5+2.0−1.5, consistent with CO originating in ejecta processed by the very late thermal pulse, rather than in the pre-existing planetary nebula. We demonstrate the existence of 2.2 × 10−6≤MCO≤ 2.7 × 10−6 M⊙ of CO ejecta outside the dust, forming a high-velocity wind of 500 ± 80 km s−1. We find evidence for significant weakening of the CO band and cooling of the dust around the central star between 2003 and 2005. The gas and dust temperatures are implausibly high for stellar radiation to be the sole contributor

The onset of photoionization in Sakurai's Object (V4334 Sgr)

We investigate the reheating of the very late thermal pulse (VLTP) object V4334 Sgr (Sakurai's Object) using radio observations from the Very Large Array, and optical spectra obtained with the Very Large Telescope. We find a sudden rise of the radio flux at 5 and 8 GHz - from <= 90 micro-Jy and 80 +/- 30 micro-Jy in February 2005 to 320 micro-Jy and 280 micro-Jy in June 2006. Optical line emission is also evolving, but the emission lines are fading. The optical line emission and early radio flux are attributed to a fast shock (and not photoionization as was reported earlier) which occurred around 1998. The fading is due to post-shock cooling and recombination. The recent rapid increase in radio flux is evidence for the onset of photoionization of carbon starting around 2005. The current results indicate an increase in the stellar temperature to 12 kK in 2006. The mass ejected in the VLTP eruption is M_ej >= 1e-4 Msol, but could be as high as 1e-2 Msol, depending mainly on the distance and the clumping factor of the outflow. We derive a distance between 1.8 and 5 kpc. A high mass loss could expose the helium layer and yield abundances compatible with those of [WC] and PG1159 stars.Comment: 4 pages, 2 figures; accepted for publication in A&A letter

Differential effects of human activity on Hawaiian spinner dolphins in their resting bays

Hawaiian spinner dolphins display predictable daily behavior, using shallow bays to rest during the daytime, bays that are also frequented by humans. All previous research on the potential response of Hawaiian spinner dolphins to human activity has been conducted visually, at the surface. In this study we take a different approach by using passive acoustic monitoring to analyze dolphin behavior and assess whether human activity affects the behavior of the animals. We used days (n=99) and hours (n=641) when dolphins were confirmed present in visual surveys between January 9, 2011 and August 15, 2012 and metrics generated from concomitant 30-second sound recordings (n=9615). Previous research found that the dolphins were predictably silent during rest and that acoustic activity matched general activity of the dolphins with higher acoustic activity before and after rest, and silence during rest. The daily pattern of dolphin whistle activity in Bay 2 and 4 (Kealakekua and Kauhako) matched what would be expected from this earlier work. However, in Bay 1 and 3 (Makako and Honaunau) there was no drop in dolphin whistle activity during rest. After assessing the relationship between time of day and dolphin acoustic activity, data on human presence were used to determine how variability in the dolphins’ acoustic activity might be explained by human activity (i.e. the number of vessels, kayaks and swimmer snorkelers present). Bay 2, the bay with the most human activity, showed no relationship between dolphin whistle activity and human presence (either vessels, kayaks, or swimmer/snorkelers). Although the relationships were weak, Bay 1 displayed a positive relationship between dolphin whistle activity and the number of vessels and swimmer/snorkelers present in the bay. Bay 4 also showed a positive relationship between dolphin whistle activity and the number of swimmer snorkelers. We also documented less sound being added to the soundscape with each additional vessel in Bay 2 when compared to Bay 1, a bay with dolphin-focused activities. We hypothesize it is not the magnitude of the activity but the focus of the activity that matters and suggest that the effect of human activity on spinner dolphin acoustic behavior should be explored in future studies. These results have implications for designing future studies as well as for ongoing efforts to protect Hawaiian spinner dolphins in their resting bays

Passive acoustic monitoring of coastally associated Hawaiian spinner dolphins, Stenella longirostris, ground-truthed through visual surveys

Effective decision making to protect coastally associated dolphins relies on monitoring the presence of animals in areas that are critical to their survival. Hawaiian spinner dolphins forage at night and rest during the day in shallow bays. Due to their predictable presence, they are targeted by dolphin-tourism. In this study, comparisons of presence were made between passive acoustic monitoring (PAM) and vessel-based visual surveys in Hawaiian spinner dolphin resting bays. DSG-Ocean passive acoustic recording devices were deployed in four bays along the Kona Coast of Hawai'i Island between January 8, 2011 and August 30, 2012. The devices sampled at 80 kHz, making 30-s recordings every four minutes. Overall, dolphins were acoustically detected on 37.1% to 89.6% of recording days depending on the bay. Vessel-based visual surveys overlapped with the PAM surveys on 202 days across the four bays. No significant differences were found between visual and acoustic detections suggesting acoustic surveys can be used as a proxy for visual surveys. Given the need to monitor dolphin presence across sites, PAM is the most suitable and efficient tool for monitoring long-term presence/absence. Concomitant photo-identification surveys are necessary to address changes in abundance over time