CC Bootis: QSO, Not Variable Halo Giant

The poorly-studied, faint (18<m_pg<19.5) variable star CC Bootis has been noted in the literature as a candidate for a halo red giant. It proves instead to be a quasi-stellar object of redshift z=0.172, and is detected as an X-ray source by ROSAT. In addition to its odd heritage, CC Boo exhibits unusually high amplitude optical variability for an optically-selected QSO.Comment: 6 pages including 1 table and 2 figures; Accepted for publication in Pub. Astr. Soc. Pacific, Vol 109, June 199

Measuring Biomarkers of Friedreich Ataxia: Implications for Clinical Research

Friedreich ataxia (FRDA) is a neurodegenerative disease caused by mutations in the frataxin (FXN) gene, resulting in reduced expression of the mitochondrial protein frataxin. While there currently is no cure for FRDA, our increasing understanding of the pathophysiology of disease has led to a surge in the development of potential treatments. As a result, there is a growing need for biological markers of disease progression and patient response to therapeutic intervention. In this thesis, we developed and validated a lateral flow “dipstick” immunoassay for the measurement of frataxin protein in multiple peripheral cell types. We measured significant differences in frataxin levels between controls, carriers, and FRDA patients, and found correlations between frataxin levels and GAA1 repeat length and age of onset. We then compared the utility of the dipstick assay as a population screening and diagnostic tool to a separate, Luminex xMAP-based immunoassay, and discuss the advantages and disadvantages of each assay in different clinical settings. The dipstick assay showed utility in a variety of clinical applications, including preliminary diagnosis of atypical FRDA patients, analysis of longitudinal frataxin measurements, correlations with changes in neurological severity, patient response to HDAC inhibitor treatment, response to chemotherapy in an FRDA case with comorbid osteosarcoma, and assessment of HDAC and SIRT gene polymorphisms on frataxin protein expression. Finally, we used Stable Isotope Labeling with Essential nutrients in Cell culture (SILEC) methodology to assess metabolic changes in transfected cells as well as primary fibroblasts and platelets isolated from FRDA patients. Using SILEC internal standards, we found that acetyl-CoA:succinyl-CoA ratios were significantly decreased in FRDA patients compared to controls, consistent with in vitro siRNA knockdown models of frataxin. Changes in CoA profiles, coupled with isotopic tracer analysis using [U-13C6]-glucose and [U-13C16]-palmitic acid, provided us with further insight into possible metabolic dysfunction in FRDA. Taken together, the results from this thesis show utility for frataxin measurements from peripheral tissues as a biomarker, and potentially provide researchers with a novel set of markers to assess metabolic dysfunction in unaffected tissues, not just in FRDA, but in any mitochondrial disorder

Observations of Post-wildfire Landcover Trends in Boreal Alaska Using a Suite of Remote Sensing Approaches

Wildfires are a common occurrence in the boreal ecosystems of the Pacific Northwest. Studies suggest that anthropogenic climate change has fostered more frequent and higher severity fires in recent decades in these forests, which may result in substantial changes in vegetation structure and ecosystem functioning. However, large-scale studies examining the linkages between changing boreal wildfire regimes and vegetation structure have historically been limited in spatial scope due to the broad area and inaccessibility of many boreal regions, including the Alaskan interior. The development and advancement of satellite remote sensing instruments and geospatial analysis techniques provide researchers with unmatched abilities to conduct large-scale studies of boreal fire-vegetation dynamics. This research utilizes publicly available multispectral Landsat imagery, Synthetic Aperture Radar imagery, Digital Elevation Models, wildfire perimeter data, and landcover classification products to gain insights into the linkages between climate, wildfire, and vegetation throughout the entire boreal ecoregion of Alaska. Analyses utilizing existing wildfire and landcover geospatial products suggest significant declines in both fire-adapted black spruce-dominated forests and fire-resistant deciduous forests from 2001 to 2016, of -50.0% and -19.3% landcover area, respectively. However, post-fire recruitment of deciduous forests far exceeds evergreen forest types in regions that had experienced one fire (3.4 times more likely) and two or more fires (4.9 times more likely), between 1970 and 2019. Novel spectral unmixing and fractional coverage analyses using evergreen, deciduous, and early successional endmembers yielded significant monotonic declines in the change in pixel proportion of evergreen forests as a function of wildfire frequency, with -2.36%, -25.35%, and -35.15% for areas of zero, one, and two or more fires, respectively. In contrast, deciduous changes in pixel proportion exhibited higher degradation in non-fire regions (-6.23%) than evergreens, lower magnitude decreases in single-fire areas (-21.59%), and a significant rebound in coverage in regions that burned two or more times over the study period (-10.04%). These findings suggest that deciduous forests are more resistant to wildfire than evergreen-dominated systems, and their recruitment following evergreen-fueled wildfires may moderate the frequency and severity of subsequent local fire regimes

An Ultraviolet-Excess Optical Candidate for the Luminous Globular Cluster X-ray Source in NGC1851

The intense, bursting X-ray source in the globular cluster NGC 1851 was one of the first cluster sources discovered, but has remained optically unidentified for 25 years. We report here on results from Hubble Space Telescope WFPC2 multicolor images in NGC 1851. Our high spatial resolution images resolve ~200 objects in the 3'' radius Einstein X-ray error circle, 40 times as many as in previous ground-based work. A color-magnitude diagram of the cluster clearly reveals a markedly UV-excess object with B~21, (U-B) ~ -0.9 only 2'' from the X-ray position. The UV-excess candidate is 0.12'' distant from a second, unremarkable star that is 0.5 mag brighter in B; thus ground-based studies of this field are probably impractical. Three other UV-excess objects are also present among the ~16,000 objects in the surveyed region of the cluster, leaving a ~5% probability that a UV-excess object has fallen in the X-ray error circle by chance. No variability of the candidate is seen in these data, although a more complete study is required. If this object is in fact the counterpart of the X-ray source, previous inferences that some globular cluster X-ray sources are optically subluminous with respect to low-mass X-ray binaries in the field are now strengthened.Comment: 13 pages including 1 table and 3 figures in AASTeX 4.0; To appear in The Astrophysical Journal Letters, volume 472 (1996 December 1). Preprint with full-resolution figures available at http://www.astro.washington.edu/deutsch/pubs/pubs.htm

Empirical Uncertainty Estimators for Astrometry from Digital Databases

In order to understand the positional uncertainties of arbitrary objects in several of the current major databases containing astrometric information, a sample of extragalactic radio sources with precise positions in the International Celestial Reference Frame (ICRF) is compared with the available positions of their optical counterparts. The discrepancies between the radio and various optical positions are used to derive empirical uncertainty estimators for the USNO-A2.0, USNO-A1.0, Guide Star Selection System (GSSS) images, and the first and second Digitized Sky Surveys (DSS-I and DSS-II). In addition, an estimate of the uncertainty when the USNO-A2.0 catalog is transferred to different image data is provided. These optical astrometric frame uncertainties can in some cases be the dominant error term when cross-identifying sources at different wavelengths.Comment: 12 pages including 2 figures and 1 table. Accepted for publication in The Astronomical Journal, October 1999. Values in Table 1 for DSS I corrected 99-07-1

Complex Velocity Fields in the Shell of T Pyxidis

We present spatially-resolved, moderate-resolution spectrophotometry of the recurrent nova T Pyx and a portion of the surrounding shell. The spectrum extracted from a strip of width 10'' centered on the star shows well-known, strong emission lines typical of old novae, plus a prominent, unfamiliar emission line at 6590 Angstroms. This line, and a weaker companion at 6540 Angstroms which we also detect, have been previously reported by Shahbaz et al., and attributed to Doppler-shifted H alpha emission from a collimated jet emerging from T Pyx. We demonstrate that these lines are instead due to [NII] 6548, 6584 from a complex velocity field in the surrounding nebula. The comments of past workers concerning the great strength of HeII 4686 in T Pyx itself are also reiterated.Comment: 8 pages including 2 figures; Accepted for publication in The Astrophysical Journal Letter

Time-Resolved Ultraviolet Observations of the Globular Cluster X-ray Source in NGC 6624: The Shortest Known Period Binary System

Using the Faint Object Spectrograph (FOS) aboard the Hubble Space Telescope, we have obtained the first time-resolved spectra of the King et al. ultraviolet-bright counterpart to the 11-minute binary X-ray source in the core of the globular cluster NGC 6624. This object cannot be readily observed in the visible, even from HST, due to a much brighter star superposed <0.1'' distant. Our FOS data show a highly statistically significant UV flux modulation with a period of 11.46+-0.04 min, very similar to the 685 sec period of the known X-ray modulation, definitively confirming the association between the King et al. UV counterpart and the intense X-ray source. The UV amplitude is very large compared with the observed X-ray oscillations: X-ray variations are generally reported as 2-3% peak-to-peak, whereas our data show an amplitude of about 16% in the 126-251 nm range. A model for the system by Arons & King predicts periodic UV fluctuations in this shortest-known period binary system, due to the cyclically changing aspect of the X-ray heated face of the secondary star (perhaps a very low mass helium degenerate). However, prior to our observations, this predicted modulation has not been detected. Employing the Arons & King formalism, which invokes a number of different physical assumptions, we infer a system orbital inclination 35deg<i<50 deg. Amongst the three best-studied UV/optical counterparts to the intense globular cluster X-ray sources, two are now thought to consist of exotic double-degenerate ultrashort period binary systems.Comment: 10 pages including 2 figures in Latex (AASTeX 4.0). Accepted for publication in vol. 482 (1997 June 10 issue) of The Astrophysical Journal (Letters

The impact of yoga on atrial fibrillation: A review of The Yoga My Heart Study

AbstractAtrial fibrillation is a common arrhythmia affecting thousands of individuals worldwide. It is a conduction disorder that causes the heart to beat irregularly and rapidly. There are a few medical approaches to manage this costly health care burden: antiarrhythmics to maintain normal sinus rhythm, beta blockers to achieve rate control while allowing atrial fibrillation to persist, and electro-physiologic intervention for rate and rhythm control. These treatments can be costly and are not without side effects. Yoga, an intervention that is available to people worldwide, has shown some promise in combating this widespread heart disorder

Pattern avoidance in binary trees

This paper considers the enumeration of trees avoiding a contiguous pattern. We provide an algorithm for computing the generating function that counts n-leaf binary trees avoiding a given binary tree pattern t. Equipped with this counting mechanism, we study the analogue of Wilf equivalence in which two tree patterns are equivalent if the respective n-leaf trees that avoid them are equinumerous. We investigate the equivalence classes combinatorially. Toward establishing bijective proofs of tree pattern equivalence, we develop a general method of restructuring trees that conjecturally succeeds to produce an explicit bijection for each pair of equivalent tree patterns.Comment: 19 pages, many images; published versio