Metal-Rich SX Phe Stars in theKeplerField

High-resolution spectroscopic observations have been made for 32 of the 34 candidate SX Phe stars identified in the Kepler field by Balona & Nemec (2012). All available long- and short-cadence Q0-Q17 Kepler photometry has been analyzed for the 34 candidates. Radial velocities (RVs), space motions (U, V, W), projected rotation veloc- ities (v sin i), spectral types, and atmospheric characteristics (Teff , log g, [M/H], vmic, etc.) were derived from ∼160 spectra taken with the ESPaDOnS spectrograph on the Canada- France-Hawaii 3.6-m telescope and with the ARCES spectrograph on the Apache Point Observatory 3.5-m telescope. Two thirds of the stars are fast rotators with v sin i > 50 km/s, including four stars with v sin i > 200 km/s. Three of the stars have (negative) RVs > 250 km/s and retrograde space motions, and seven stars have total space motions > 400 km/s. All the spectroscopically measured SX Phe candidates have positions in a Toomre diagram that are consistent with being bona fide halo and thick-disk stars. Although several stars show a marked metal weakness, the mean [Fe/H] of the sample is near 0.0 dex (σ ∼ 0.25 dex), which is considerably more metal-rich than is normally expected for a sample of Pop. II stars. Observed pulsation frequency modulations and optical time delays suggest that at least eight of the SX Phe stars are in binary systems, some of which show signif- icant RV variations. Six of the time-delay binaries have secondary masses ranging from 0.05 to 0.70 Mo and orbital periods in the range 9 to 1570 days. Another star appears to be an ellipsoidal variable with a 2.3-day orbital period; and two other systems have orbital periods longer than the ∼4-year sampling interval of the Kepler data

Signaling mechanisms for gene regulation by metals and metal mixtures

Numerous epidemiological studies associate chronic inhalation of metal mixtures with increased risk of pulmonary diseases. Although exposure to metal mixtures is of great public health relevance, the integration of cellular responses to metals within these mixtures that promote disease is poorly understood. This dissertation investigated the hypothesis that chromium (VI) (Cr(VI)) stimulates signaling that alters transcriptional complexes to silence protective gene induction by nickel (Ni). In airway epithelial (BEAS-2B) cells, Cr(VI) activated signal transducer and activator of transcription 1 (STAT1)-dependent signaling within 1 h of exposure. This activation was dependent on Src family kinases (SFKs) since inhibiting SFKs prevented Cr(VI)-stimulated STAT1 signaling. Moreover, Cr(VI) activated STAT1 in wild-type mouse embryonic fibroblast (MEF) cells, but no response was observed in MEF cells null for the SFKs, Src, Yes, and Fyn. However, reconstituting human Fyn in the deficient MEF cells restored the Cr(VI) response. These data indicate that Cr(VI)-activated STAT1 is mediated by Fyn. This signaling may be detrimental as STAT1 has been implicated as an inflammatory mediator in asthma patients that is specifically activated in bronchial epithelial cells (1). Metallothionein (MT) and vascular endothelial growth factor A (VEGFA) are involved in protecting the lung from injury by sequestering metals and promoting wound repair, respectively. Ni-induced MT2A, the most abundant human isoform, required zinc (Zn) redistribution which directly activated metal transcription factor-1 (MTF-1). A prolonged induction was mediated by secondary signaling pathways. Cr(VI) negatively regulated the secondary pathway and had no effect on Zn mobilization. For VEGFA induction, Ni activated a complex signaling cascade involving ERK. Ni-stimulated ERK was upstream of hypoxia-inducible factor-1á (HIF-1á) and Src-mediated Sp1 transactivation. Cr(VI) inhibited Ni-activated ERK, HIF-1á stabilization, Src phosphorylation, and VEGFA induction. The current study demonstrated that Cr(VI)-activated STAT1 is responsible for the silencing of inducible genes. In BEAS-2B cells stably expressing STAT1 shRNA, Cr(VI) no longer had an inhibitory effect on Ni-induced MT or VEGFA mRNA expression and positively interacted with Ni to induce both genes. These data indicate that Cr(VI)-activated STAT1 may play a role in the pathogenesis of Cr(VI)-induced pulmonary diseases by silencing the protective gene transcription in the airway epithelium

CCD time-series photometry of the globular cluster NGC 5053: RR Lyrae, Blue Stragglers and SX Phoenicis stars revisited

We report the results of CCD $V$, $r$ and $I$ time-series photometry of the globular cluster NGC 5053. New times of maximum light are given for the eight known RR Lyrae stars in the field of our images and their periods are revised. Their $V$ light curves were Fourier decomposed to estimate their physical parameters. A discussion on the accuracy of the Fourier-based iron abundances, temperatures, masses and radii is given. New periods are found for the 5 known SX Phe stars and a critical discussion of their secular period changes is offered. The mean iron abundance for the RR Lyrae stars is found to be [Fe/H] $\sim -1.97 \pm 0.16$ and lower values are not supported by the present analysis. The absolute magnitude calibrations of the RR Lyrae stars yield an average true distance modulus of $16.12 \pm 0.04$ or a distance of $16.7 \pm 0.3$ kpc. Comparison of the observational CMD with theoretical isochrones indicates an age of $12.5 \pm 2.0$ Gyrs for the cluster. A careful identification of all reported Blue Stragglers (BS) and their $V,I$ magnitudes leads to the conclusion that BS12, BS22, BS23 and BS24 are not BS. On the other hand, three new BS are reported. Variability was found in seven BS, very likely of the SX Phe type in five of them, and in one red giant star. The new SX Phe stars follow established $PL$ relationships and indicate a distance in agreement with the distance from the RR Lyrae stars.Comment: 21 pages, 16 figures, 11 tables. Accepted for publication in MNRA

Dakotah Poesy (1991)

A literary magazine presenting the creative work of the students, staff, and friends of Dakota State University

Antimicrobial resistance and clonality in Acinetobacter baumannii

The aim of this thesis was to obtain insight into the epidemiology and molecular basis of multidrug resistance of Acinetobacter baumannii at the population level. To this aim a number of studies were performed on strains mainly from the Czech Republic (CR) which have shown in particular that (i) the vast majority of multidrug resistant (MDR) clinical isolates of A. baumannii from CR belong to clonal lineages termed EU clone I and II; (ii) these two clones have predominated among MDR hospital isolates in CR since at least 1991; (iii) recent emergence of A. baumannii resistance to carbapenems in CR was associated with the country-wide spread of a subclone of EU clone II; (iv) multidrug resistance is a general feature of strains of EU clones I and II, yet strains belonging to one clone may vary in the content of resistance genes; (v) upregulation of genes intrinsic to A. baumannii as well as horizontal acquisition of resistance genes can be sources of development of multidrug resistance and intraclonal diversification; (vi) the genes encoding the non-specific efflux system AdeABC are present in nearly all A. baumannii strains, yet the AdeABC overexpression is seen mostly in MDR strains harbouring additional resistance genes.UBL - phd migration 201

Human PrimPol mutation associated with high myopia has a DNA replication defect

PrimPol is a primase-polymerase found in humans, and other eukaryotes, involved in bypassing lesions encountered during DNA replication. PrimPol employs both translesion synthesis and repriming mechanisms to facilitate lesion bypass by the replisome. PrimPol has been reported to be a potential susceptibility gene associated with the development of myopia. Mutation of tyrosine 89 to aspartic acid (PrimPolY89D) has been identified in a number of cases of high myopia, implicating it in the aetiology of this disorder. Here, we examined whether this mutation resulted in any changes in the molecular and cellular activities associated with human PrimPol. We show that PrimPolY89D has a striking decrease in primase and polymerase activities. The hydrophobic ring of tyrosine is important for retaining wild-type extension activity. We also demonstrate that the decreased activity of PrimPolY89D is associated with reduced affinities for DNA and nucleotides, resulting in diminished catalytic efficiency. Although the structure and stability of PrimPolY89D is altered, its fidelity remains unchanged. This mutation also reduces cell viability after DNA damage and significantly slows replication fork rates in vivo. Together, these findings establish that the major DNA replication defect associated with this PrimPol mutant is likely to contribute to the onset of high myopia

The Star Formation History of the Carina Dwarf Galaxy

We have analyzed deep B and V photometry of the Carina dwarf spheroidal reaching below the old main-sequence turnoff to about V = 25. Using simulated color-magnitude diagrams to model a range of star formation scenarios, we have extracted a detailed, global star formation history. Carina experienced three significant episodes of star formation at about 15 Gyr, 7 Gyr, and 3 Gyr. Contrary to the generic picture of galaxy evolution, however, the bulk of star formation, at least 50%, occured during the episode 7 Gyr ago, which may have lasted as long as 2 Gyr. For unknown reasons, Carina formed only 10-20% of its stars at an ancient epoch and then remained quiescent for more than 4 Gyr. The remainder (~30%) formed relatively recently, only 3 Gyr ago. Interest in the local population of dwarf galaxies has increased lately due to their potential importance in the understanding of faint galaxy counts. We surmise that objects like Carina, which exhibits the most extreme episodic behavior of any of the dwarf spheroidal companions to the Galaxy, are capable of contributing to the observed excess of blue galaxies at B = 24 only if the star formation occurred instantaneously.Comment: 23 pages of text, 20 figures, 8 tables. AJ, in pres