Physical Characteristics and Classification of the Large Amplitude Variable Star V1719 Cygni

Pulsating stars are used as standard candles which are helpful in determining distances to stellar objects along with the relationship between their period and apparent luminosity. The focus of this study was the variable star, V1719 Cygni, which is often classified as a Delta (δ) Scuti star, but there exists debate that it should be classified as a RR Lyrae star due to its abnormal light curve and similar characteristics between the two variable star categories. Observational data was taken in 2019 using the Las Cumbres Observatory international telescope network. The resulting data were calibrated using comparison stars in the field of known magnitude. We performed aperture photometry in the V-, B-, i- and z- photometric bands. The period was then found using the string method which determines the most probable period. The average period was found to be 0.269 days with an error of 0.0005. The distance was calculated using the previously established period-luminosity relation for both δ Scuti and RR Lyrae stars to determine which classification fits our data best. The distance calculation was more closely aligned with previous results when using the δ Scuti relationship as compared to the RR Lyrae relationship. Based on these results, we conclude that V1719 Cygni should be classified as a high-amplitude δ Scuti variable star. It is important to note that period-luminosity relationships have not been established in all photometric bands, but the period measurements obtained in the B-, i-, and z- bands will help to establish that relationship

On the Bartnik extension problem for the static vacuum Einstein equations

We develop a framework for understanding the existence of asymptotically flat solutions to the static vacuum Einstein equations with prescribed boundary data consisting of the induced metric and mean curvature on a 2-sphere. A partial existence result is obtained, giving a partial resolution of a conjecture of Bartnik on such static vacuum extensions. The existence and uniqueness of such extensions is closely related to Bartnik's definition of quasi-local mass.Comment: 33 pages, 1 figure. Minor revision of v2. Final version, to appear in Class. Quantum Gravit

The haloes and environments of nearby galaxies (HERON) -- III. A 45 kpc spiral structure in the GLSB galaxy UGC 4599

We use a 0.7-m telescope in the framework of the Halos and Environments of Nearby Galaxies (HERON) survey to probe low surface brightness structures in nearby galaxies. One of our targets, UGC 4599, is usually classified as an early-type galaxy surrounded by a blue ring making it a potential Hoag's Object analog. Prior photometric studies of UGC 4599 were focused on its bright core and the blue ring. However, the HERON survey allows us to study its faint extended regions. With an eight hour integration, we detect an extremely faint outer disk with an extrapolated central surface brightness of $\mu_\mathrm{0,d}(r)=25.5$ mag arcsec$^{-2}$ down to 31 mag arcsec$^{-2}$ and a scale length of 15 kpc. We identify two distinct spiral arms of pitch angle ~6{\deg} surrounding the ring. The spiral arms are detected out to ~45 kpc in radius and the faint disk continues to ~70 kpc. These features are also seen in the GALEX FUV and NUV bands, in a deep u-band image from the 4.3m Lowell Discovery Telescope (which reveals inner spiral structure emerging from the core), and in HI. We compare this galaxy to ordinary spiral and elliptical galaxies, giant low surface brightness (GLSB) galaxies, and Hoag's Object itself using several standard galaxy scaling relations. We conclude that the pseudobulge and disk properties of UGC 4599 significantly differ from those of Hoag's Object and of normal galaxies, pointing toward a GLSB galaxy nature and filamentary accretion of gas to generate its outer disk.Comment: 17 pages, 14 figures, accepted for publication in MNRA

The Halos and Environments of Nearby Galaxies (HERON) Survey

We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L* and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as M_V=-18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitously discovered a dwarf galaxy undergoing tidal disruption in the halo of NGC 4449, we found no comparable examples in our general survey. A search for similar examples in the Local Volume identified hcc087, a tidally disrupting dwarf galaxy in the Hercules Cluster, but we do not confirm an anomalously large half-light radius reported for the dwarf VCC 1661

Systematic overviews of partnership principles and strategies identified from health research about spinal cord injury and related health conditions:A scoping review

Study design: Scoping review.Objective: To identify and provide systematic overviews of partnership principles and strategies identified from health research about spinal cord injury (SCI) and related health conditions.Methods: Four health electronic databases (Medline, Embase, CINAHL, PsycINFO) were searched from inception to March 2019. We included articles that described, reflected, and/or evaluated one or more collaborative research activities in health research about SCI, stroke, multiple sclerosis, Parkinson's disease, amputation, cerebral palsy, spina bifida, amyotrophic lateral sclerosis, acquired brain injury, or wheelchair-users. Partnership principles (i.e. norms or values) and strategies (i.e. observable actions) were extracted and analyzed using directed qualitative content analysis.Results: We included 39 articles about SCI (n = 13), stroke (n = 15), multiple sclerosis (n = 5), amputation (n = 2), cerebral palsy (n = 2), Parkinson's disease (n = 1), and wheelchair users (n = 1). We extracted 110 principles and synthesized them into 13 overarching principles. Principles related to building and maintaining relationships between researchers and research users were most frequently reported. We identified 32 strategies that could be applied at various phases of the research process and 26 strategies that were specific to a research phase (planning, conduct, or dissemination).Conclusion: We provided systematic overviews of principles and strategies for research partnerships. These could be used by researchers and research users who want to work in partnership to plan, conduct and/or disseminate their SCI research. The findings informed the development of the new SCI Integrated Knowledge Translation Guiding Principles (www.iktprinciples.com) and will support the implementation of these Principles within the SCI research system.</p

High-Redshift Quasars Found in Sloan Digital Sky Survey Commissioning Data II: The Spring Equatorial Stripe

This is the second paper in a series aimed at finding high-redshift quasars from five-color (u'g'r'i'z') imaging data taken along the Celestial Equator by the Sloan Digital Sky Survey (SDSS) during its commissioning phase. In this paper, we present 22 high-redshift quasars (z>3.6) discovered from ~250 deg^2 of data in the spring Equatorial Stripe, plus photometry for two previously known high-redshift quasars in the same region of sky. Our success rate of identifying high-redshift quasars is 68%. Five of the newly discovered quasars have redshifts higher than 4.6 (z=4.62, 4.69, 4.70, 4.92 and 5.03). All the quasars have i* < 20.2 with absolute magnitude -28.8 < M_B < -26.1 (h=0.5, q_0=0.5). Several of the quasars show unusual emission and absorption features in their spectra, including an object at z=4.62 without detectable emission lines, and a Broad Absorption Line (BAL) quasar at z=4.92.Comment: 28 pages, AJ in press (Jan 2000), final version with minor changes; high resolution finding charts available at http://www.astro.princeton.edu/~fan/paper/qso2.htm

Contributions of cortical and subcortical circuits to reaction times and excitability levels in complex tasks

The way humans interact with their environment can range from simple reaching and grasping movements to remarkably complex movement patterns. Complexity increases reaction time (RT) and alters the excitability of the motor system. However, this area of research lacks a detailed description of the locus of the processes involved in the successful preparation and execution of complex movements. As the motor system can be influenced by cortical, spinal, and peripheral components, the overall purpose across the four studies of this thesis was to assess separately how they contribute to complex movement preparation and execution. The purpose of study 1 was to describe how movement complexity affected whole-body anticipatory postural adjustments (APAs). In this study, it was shown that APA onset times increased prior to an imperative stimulus (IS) as movements became more complex, demonstrating the motor system integrated movement complexity into a global motor plan. To isolate corticospinal contributions to this motor plan, study 2 used transcranial magnetic stimulation (TMS) to demonstrate that motor evoked potentials (MEPs) increased as a consequence of movement complexity. Study 3 used a combination of TMS and transmastoid stimulation to assess the cortical and spinal contributions to the increase of the MEP. This study demonstrated that increases in MEP due to movement complexity were mediated at the spinal level. Furthermore, it was shown that motoneuron excitability increases at least 50% earlier than previously described in the literature. As the spinal cord also receives descending input independent of cortical influence (e.g. extrapyramidal pathways), the purpose of study 4 was to examine if the vestibulomotor system had a role in the preparation of complex movements. This study demonstrated that vestibular-evoked responses are greater during the preparation of complex movements in both the upper and lower limbs. Prior to this study, the vestibulomotor pathway was shown to be involved in the online control of arm movements; however, this demonstrates the vestibulomotor pathway is also involved in the preparation of movement. Overall, this thesis demonstrates a complex interaction of multiple elements of the motor system in the execution of movement.Health and Social Development, Faculty of (Okanagan)Health and Exercise Sciences, School of (Okanagan)Graduat

Mean (+/− SE) motor-evoked potential (MEP) amplitude during the RT interval expressed as a percentage of maximal MEP (Mmax) for 10 ms time bins prior to EMG onset.

<p>The number of trials making up the mean for each of the time points (secondary axis) is represented by columns. The asterisk (*) denotes a significant increase in MEP amplitude as EMG onset approaches.</p