1,115 results on '"Boyd, David"'
Search Results
2. Diet-induced obesity affects influenza disease severity and transmission dynamics in ferrets.
- Author
-
Meliopoulos, Victoria, Honce, Rebekah, Livingston, Brandi, Hargest, Virginia, Freiden, Pamela, Lazure, Lauren, Brigleb, Pamela, Karlsson, Erik, Sheppard, Heather, Allen, E, Boyd, David, Thomas, Paul, and Schultz-Cherry, Stacey
- Subjects
Animals ,Ferrets ,Obesity ,Orthomyxoviridae Infections ,Disease Models ,Animal ,Lung ,Severity of Illness Index ,Diet ,Humans ,Virus Shedding ,Influenza ,Human - Abstract
Obesity, and the associated metabolic syndrome, is a risk factor for increased disease severity with a variety of infectious agents, including influenza virus. Yet, the mechanisms are only partially understood. As the number of people, particularly children, living with obesity continues to rise, it is critical to understand the role of host status on disease pathogenesis. In these studies, we use a diet-induced obese ferret model and tools to demonstrate that, like humans, obesity resulted in notable changes to the lung microenvironment, leading to increased clinical disease and viral spread to the lower respiratory tract. The decreased antiviral responses also resulted in obese animals shedding higher infectious virus for a longer period, making them more likely to transmit to contacts. These data suggest that the obese ferret model may be crucial to understanding obesitys impact on influenza disease severity and community transmission and a key tool for therapeutic and intervention development for this high-risk population.
- Published
- 2024
3. A Dragon's Flame of Many Colours: Multi-wavelength Observations of Flares from the Active M Binary CR Draconis
- Author
-
Jackman, James A. G., Shkolnik, Evgenya L., Loyd, R. O. Parke, Richey-Yowell, Tyler, Llama, Joe, Boyd, David, Buchheim, Bob, Iadevaia, David, Martin, Jack, Sims, Forrest, Walker, Gary, and Wetmore, John
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We present the results of a multi-wavelength Pro-Am campaign to study the behaviour of flares from the active M1.5V star binary CR Draconis. CR Dra was observed with TESS 20-s photometry, Swift near-UV (NUV) grism spectroscopy and with ground-based optical photometry and spectroscopy from a global collaboration of amateur astronomers. We detected 14 flares with TESS and Swift simultaneously, one of which also had simultaneous ground-based photometry and spectroscopy. We used the simultaneous two-colour optical and NUV observations to characterise the temperature evolution of the flare and test the accuracy of using optical data to predict NUV emission. We measured a peak temperature of $7100^{+150}_{-130}$ K for this flare, cooler than the typically assumed 9000 K blackbody model used by flare studies. We also found that the 9000 K blackbody overestimated the NUV flux for other flares in our sample, which we attributed to our Swift observations occurring during flare decays, highlighting the phase-dependence for the accuracy of flare models., Comment: Accepted for publication in Monthly Notices of the Royal Astronomical Society
- Published
- 2024
4. Spectroscopic and Photometric Study of the Asymptotic Giant Branch Star T Cephei
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Spectroscopy and photometry of the Asymptotic Giant Branch star T Cephei were recorded concurrently on 36 nights during its 387 day pulsation cycle in 2022. Photometry was used to calibrate all spectra in absolute flux. We report on the variation of B and V magnitudes, B-V colour index, spectral type, effective temperature and Balmer emission line flux during one complete pulsation cycle., Comment: 7 pages, 10 figures, accepted for publication in the Journal of the AAVSO. arXiv admin note: text overlap with arXiv:2107.10061
- Published
- 2023
5. TESS photometry of the nova eruption in V606 Vul: asymmetric photosphere and multiple ejections?
- Author
-
Sokolovsky, Kirill V., Aydi, Elias, Malanchev, Konstantin, Burke, Colin J., Mukai, Koji, Sokoloski, J. L., Metzger, Brian D., Atapin, Kirill E., Belinski, Aleksandre A., Chen, Yu-Ching, Chomiuk, Laura, Dubovsky, Pavol A., Faucher-Giguere, Claude-Andre, Hounsell, Rebekah A., Ikonnikova, Natalia P., Lander, Vsevolod Yu., Li, Junyao, Linford, Justin D., Mioduszewski, Amy J., Molina, Isabella, Munari, Ulisse, Potanin, Sergey A., Quimby, Robert M., Rupen, Michael P., Scaringi, Simone, Shatsky, Nicolai I., Shen, Yue, Steinberg, Elad, Stone, Zachary, Tatarnikov, Andrey M., Vurm, Indrek, Williams, Montana N., Azcona, Antonio Agudo, Boyd, David, Bean, Stewart, Braunwarth, Horst, Blackwell, John, Bolzoni, Simone, Casas, Ricard, Fernandez, David Cejudo, Dubois, Franky, Foster, James, Farfan, Rafael, Galdies, Charles, Hodge, John, Gallego, Jose Prieto, Lane, David J., Larsson, Magnus, Lindner, Peter, Logie, Ludwig, Mantero, Andrea, Aimar, Mario Morales, Menzies, Kenneth, Nakonechny, Keith, Philpot, Jerry, Filho, Antonio Padilla, Ramey, Brian, Rau, Steve, Reina, Esteban, Romanov, Filipp D., Ruocco, Nello, Shears, Jeremy, Serreau, Marc, Schmidt, Richard, Solomonov, Yuri, Tracy, Bob, Tulloch, Gord, Tomlin, Ray, Tordai, Tamas, Vanaverbeke, Siegfried, and Wenzel, Klaus
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Lightcurves of many classical novae deviate from the canonical "fast rise - smooth decline" pattern and display complex variability behavior. We present the first TESS-space-photometry-based investigation of this phenomenon. We use TESS Sector 41 full-frame images to extract a lightcurve of the slow Galactic nova V606 Vul that erupted nine days prior to the start of the TESS observations. The lightcurve covers the first of two major peaks of V606 Vul that was reached 19 days after the start of the eruption. The nova reached its brightest visual magnitude V=9.9 in its second peak 64 days after the eruption onset, following the completion of Sector 41 observations. To increase the confidence level of the extracted lightcurve, we performed the analysis using four different codes implementing the aperture photometry (Lightkurve, VaST) and image subtraction (TESSreduce, tequila_shots) and find good agreement between them. We performed ground-based photometric and spectroscopic monitoring to complement the TESS data. The TESS lightcurve reveals two features: periodic variations (0.12771d, 0.01mag average peak-to-peak amplitude) that disappeared when the source was within 1mag of peak optical brightness and a series of isolated mini-flares (with peak-to-peak amplitudes of up to 0.5mag) appearing at seemingly random times. We interpret the periodic variations as the result of azimuthal asymmetry of the photosphere engulfing the nova-hosting binary that was distorted by and rotating with the binary. Whereas we use spectra to associate the two major peaks in the nova lightcurve with distinct episodes of mass ejection, the origin of mini-flares remains elusive., Comment: 31 pages, 10 figures, submitted to ApJ; comments welcome
- Published
- 2023
6. Necroptosis blockade prevents lung injury in severe influenza
- Author
-
Gautam, Avishekh, Boyd, David F., Nikhar, Sameer, Zhang, Ting, Siokas, Ioannis, Van de Velde, Lee-Ann, Gaevert, Jessica, Meliopoulos, Victoria, Thapa, Bikash, Rodriguez, Diego A., Cai, Kathy Q., Yin, Chaoran, Schnepf, Daniel, Beer, Julius, DeAntoneo, Carly, Williams, Riley M., Shubina, Maria, Livingston, Brandi, Zhang, Dingqiang, Andrake, Mark D., Lee, Seungheon, Boda, Raghavender, Duddupudi, Anantha L., Crawford, Jeremy Chase, Vogel, Peter, Loch, Christian, Schwemmle, Martin, Fritz, Lawrence C., Schultz-Cherry, Stacey, Green, Douglas R., Cuny, Gregory D., Thomas, Paul G., Degterev, Alexei, and Balachandran, Siddharth
- Published
- 2024
- Full Text
- View/download PDF
7. TU Tau B: The Peculiar 'Eclipse' of a possible proto-Barium Giant
- Author
-
Gray, Richard O., Corbally, Christopher J., Briley, Michael M., McKay, Adam, Sims, Forrest, Boyd, David, Boussin, Christophe, McGahee, Courtney E., Buchheim, Robert, Walker, Gary, Iadevaia, David, Fernandez, David Cejudo, Lemay, Damien, Martin, Jack, Grubb, Jim, Stiewing, Albert, Daglen, Joseph, Shank, Keith, Andrews, Sydney, Barnhardt, Nick, Clark, Rebekah, Corman, Hunter, Gomes, Sabina, Jonnalagadda, Agastya, McDaries, Theo, Mills, Ava, Newsom, Will, Slate, Andrew, and Watts, Michael
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
TU Tau (= HD 38218 = HIP 27135) is a binary system consisting of a C-N carbon star primary and an A-type secondary. We report on new photometry and spectroscopy which tracked the recent disappearance of the A-star secondary. The dimming of the A-star was gradual and irregular, with one or more brief brightenings, implying the presence of nonhomogeneities in the carbon star outflow. We also present evidence that the A-star is actively accreting s-process enriched material from the carbon star and suggest that it will therefore eventually evolve into a Barium giant. This is an important system as well because the A-type star can serve as a probe of the outer atmosphere of the carbon star., Comment: 9 pages, 9 figures, 4 tables, a number of amateur observatories made significant contributions to this research. Paper accepted for publication in The Astronomical Journal
- Published
- 2023
- Full Text
- View/download PDF
8. Long-term Study of Changes in the Orbital Periods of 18 Eclipsing SW Sextantis Stars
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
SW Sex stars are an informal sub-class of eclipsing nova-like cataclysmic variables. We report 934 new eclipse times measured over the past 17 years for HS 0728+6738 (V482 Cam), SW Sex, DW UMa, HS 0129+2933 (TT Tri), V1315 Aql, PX And, HS 0455+8315, HS 0220+0603, BP Lyn, BH Lyn, LX Ser, UU Aqr, V1776 Cyg, RW Tri, 1RXS J064434.5+334451, AC Cnc, V363 Aur, and BT Mon. When combined with published eclipse times going back in some cases many decades, we show that these binary systems exhibit a range of behaviors, including increasing, decreasing, and possibly oscillating orbital periods. Nevertheless, the duration of these observations is still not long enough to be able to make reliable quantitative statements about their long term behaviors. In addition to these long term trends, we also observed rapid and unusual decreases in the orbital periods of SW Sex and RW Tri during 2017 and 2018, respectively., Comment: 17 pages, 6 figures
- Published
- 2023
9. Combined Spectroscopic and Photometric Analysis of Flares in the Dwarf M Star EV Lacertae
- Author
-
Boyd, David, Buchheim, Robert, Curry, Sean, Parks, Frank, Shank, Keith, Sims, Forrest, Walker, Gary, Wetmore, John, and Jackman, James
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We report results of an observing campaign to study the dwarf M flare star EV Lacertae. Between October 2021 and January 2022 we obtained concurrent B band photometry and low resolution spectroscopy of EV Lac on 39 occasions during 10 of which we observed flares with amplitude greater than 0.1 magnitude. Spectra were calibrated in absolute flux using concurrent photometry and flare-only spectra obtained by subtracting mean quiescent spectra. We measured B band flare energies between Log E = 30.8 and 32.6 erg. In the brightest flares we measured temporal development of flare flux in H I and He I emission lines and in the adjacent continuum and found that flux in the continuum subsided more rapidly than in the emission lines. Although our time resolution was limited, in our brightest flare we saw flux in the continuum clearly peaking before flux in the emission lines. We observed a progressive decrease in flare energy from H\b{eta} to H{\delta}. On average we found 37% of B band flare energy appeared in the H\b{eta} to H{\epsilon} emission lines with the remainder contributing to a rise in continuum flux. We measured black-body temperatures for the brightest flares between 10,500 +- 700 K and 19,500 +- 500 K and found a linear relationship between flare temperature and continuum flux at 4170 {\AA}. Balmer lines in flare-only spectra were well fitted by Gaussian profiles with some evidence of additional short-lived blue-shifted emission at the flare peak., Comment: 12 pages, 13 figures, accepted for publication in the Journal of the AAVSO
- Published
- 2023
10. Pulmonary inflammation and fibroblast immunoregulation: from bench to bedside.
- Author
-
Ghonim, Mohamed, Boyd, David, Flerlage, Tim, and Thomas, Paul
- Subjects
Humans ,Pneumonia ,Inflammation ,Fibroblasts ,Asthma ,Pulmonary Disease ,Chronic Obstructive - Abstract
In recent years, there has been an explosion of interest in how fibroblasts initiate, sustain, and resolve inflammation across disease states. Fibroblasts contain heterogeneous subsets with diverse functionality. The phenotypes of these populations vary depending on their spatial distribution within the tissue and the immunopathologic cues contributing to disease progression. In addition to their roles in structurally supporting organs and remodeling tissue, fibroblasts mediate critical interactions with diverse immune cells. These interactions have important implications for defining mechanisms of disease and identifying potential therapeutic targets. Fibroblasts in the respiratory tract, in particular, determine the severity and outcome of numerous acute and chronic lung diseases, including asthma, chronic obstructive pulmonary disease, acute respiratory distress syndrome, and idiopathic pulmonary fibrosis. Here, we review recent studies defining the spatiotemporal identity of the lung-derived fibroblasts and the mechanisms by which these subsets regulate immune responses to insult exposures and highlight past, current, and future therapeutic targets with relevance to fibroblast biology in the context of acute and chronic human respiratory diseases. This perspective highlights the importance of tissue context in defining fibroblast-immune crosstalk and paves the way for identifying therapeutic approaches to benefit patients with acute and chronic pulmonary disorders.
- Published
- 2023
11. Indoleamine 2,3-dioxygenase 1 regulates cell permissivity to astrovirus infection
- Author
-
Cortez, Valerie, Livingston, Brandi, Sharp, Bridgett, Hargest, Virginia, Papizan, James B, Pedicino, Natalie, Lanning, Sarah, Jordan, Summer Vaughn, Gulman, Jacob, Vogel, Peter, DuBois, Rebecca M, Crawford, Jeremy Chase, Boyd, David F, Pruett-Miller, Shondra M, Thomas, Paul G, and Schultz-Cherry, Stacey
- Subjects
Medical Microbiology ,Biomedical and Clinical Sciences ,Immunology ,Infectious Diseases ,Digestive Diseases ,2.1 Biological and endogenous factors ,Aetiology ,Infection ,Animals ,Humans ,Mice ,Astroviridae Infections ,Caco-2 Cells ,Indoleamine-Pyrrole 2 ,3 ,-Dioxygenase ,Interferons ,Tryptophan ,Biological Sciences ,Medical and Health Sciences - Abstract
Astroviruses cause a spectrum of diseases spanning asymptomatic infections to severe diarrhea, but little is understood about their pathogenesis. We previously determined that small intestinal goblet cells were the main cell type infected by murine astrovirus-1. Here, we focused on the host immune response to infection and inadvertently discovered a role for indoleamine 2,3-dioxygenase 1 (Ido1), a host tryptophan catabolizing enzyme, in the cellular tropism of murine and human astroviruses. We identified that Ido1 expression was highly enriched among infected goblet cells, and spatially corresponded to the zonation of infection. Because Ido1 can act as a negative regulator of inflammation, we hypothesized it could dampen host antiviral responses. Despite robust interferon signaling in goblet cells, as well as tuft cell and enterocyte bystanders, we observed delayed cytokine induction and suppressed levels of fecal lipocalin-2. Although we found Ido-/- animals were more resistant to infection, this was not associated with fewer goblet cells nor could it be rescued by knocking out interferon responses, suggesting that IDO1 instead regulates cell permissivity. We characterized IDO1-/- Caco-2 cells and observed significantly reduced human astrovirus-1 infection. Together this study highlights a role for Ido1 in astrovirus infection and epithelial cell maturation.
- Published
- 2023
12. The human right to a clean, healthy and sustainable ocean
- Author
-
Bennett, Nathan J., Morgera, Elisa, and Boyd, David
- Published
- 2024
- Full Text
- View/download PDF
13. Evidence of abrupt changes in the orbital periods of two cataclysmic variables
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We report evidence from eclipse timing that two otherwise apparently normal cataclysmic variables have experienced abrupt changes in their orbital periods. The orbital period of HS 2325+8205 increased by 22.15 msec (1.3 x 10-6 of the orbital period) around 1 February 2011 and the orbital period of EP Dra increased by 4.51 msec (7.2 x 10-7 of the orbital period) around 7 December 2001. In neither case was there any apparent change in the subsequent behaviour of the system. These changes are currently unexplained., Comment: 10 pages, 4 figures, accepted for publication in the Journal of the British Astronomical Association
- Published
- 2022
14. Kitses Rides Again
- Author
-
Boyd, David
- Published
- 2007
- Full Text
- View/download PDF
15. Hospital entrance smoking is reduced by broadcasting recorded antitobacco messages from Australian primary school children over entrance public address system
- Author
-
Webb, Ashley, Tascone, Belinda, Wickham, Lucy, Webb, Gemma, Wijeyaratne, Avisha, Boyd, David Thomas, and Leong, Samuel
- Published
- 2021
16. Investigating the low-flux states in six Intermediate Polars
- Author
-
Covington, Ava E., Shaw, Aarran W., Mukai, Koji, Littlefield, Colin, Heinke, Craig O., Plotkin, Richard M., Barrett, Doug, Boardman, James, Boyd, David, Brincat, Stephen M., Carstens, Rolf, Collins, Donald F., Cook, Lewis M., Cooney, Walter R., Fernández, David Cejudo, Dufoer, Sjoerd, Dvorak, Shawn, Galdies, Charles, Goff, William, Hambsch, Franz-Josef, Johnston, Steve, Jones, Jim, Menzies, Kenneth, Monard, Libert A. G., Morelle, Etienne, Nelson, Peter, Öğmen, Yenal, Rock, John W., Sabo, Richard, Seargeant, Jim, Stone, Geoffrey, Ulowetz, Joseph, and Vanmunster, Tonny
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
We present optical photometry of six intermediate polars that exhibit transitions to a low-flux state. For four of these systems, DW Cnc, V515 And, V1223 Sgr and RX J2133.7+5107, we are able to perform timing analysis in and out of the low states. We find that, for DW Cnc and V515 And, the dominant periodicities in the light curves change as the flux decreases, indicating a change in the sources' accretion properties as they transition to the low state. For V1223 Sgr we find that the variability is almost completely quenched at the lowest flux, but do not find evidence for a changing accretion geometry. For RX J2133.7+5107, the temporal properties do not change in the low state, but we do see a period of enhanced accretion that is coincident with increased variability on the beat frequency, which we do not associate with a change in the accretion mechanisms in the system., Comment: 19 pages, 10 figures, accepted for publication in ApJ. The authors recommend downloading the PDF of this paper, as it takes a while to render online
- Published
- 2022
- Full Text
- View/download PDF
17. ASAS J071404+7004.3 -- a close, bright nova-like cataclysmic variable with gusty winds
- Author
-
Inight, keith, Gaensicke, Boris, Blondel, Dominic, Boyd, David, Ashley, Richard, Knigge, Christian, Long, Knox, Marsh, Tom, McCleery, Jack, Scaringi, Simone, Steeghs, Danny, Thorstensen, John, Vanmunster, Tonny, and Wheatley, Peter
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - High Energy Astrophysical Phenomena - Abstract
Despite being bright ($V=12$) and nearby ($d=212$ pc) ASAS J071404+7004.3 has only recently been identified as a nova-like cataclysmic variable. We present time-resolved optical spectroscopy obtained at the Isaac Newton Telescope together with $\textit{Swift}$ X-ray and ultraviolet observations. We combined these with $\textit{TESS}$ photometry and find a period of 3.28h and a mass transfer rate of $4-9 \times 10^{-9} M_{sun}/yr$. Historical photometry shows at least one low state establishing the system as a VY Scl star. Our high-cadence spectroscopy also revealed rapidly changing winds emanating from the accretion disc. We have modelled these using the Monte Carlo PYTHON code and shown that all the emission lines could emanate from the wind - which would explain the lack of double-peaked lines in such systems. In passing,we discuss the effect of variability on the position of cataclysmic variables in the $\textit{Gaia}$ Hertzsprung-Russell diagram., Comment: Accepted for publication by MNRAS. 20 pages, 14 figures
- Published
- 2021
- Full Text
- View/download PDF
18. Spectroscopic and photometric study of the Mira stars SU Camelopardalis and RY Cephei
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Miras are fascinating stars. A kappa-mechanism in their atmosphere drives pulsations which produce changes in their photometric brightness, apparent spectral type and effective temperature. These pulsations also drive the formation of Balmer emission lines in the spectrum. This behaviour can be observed and investigated with small telescopes. We report on a three-year project combining spectroscopy and photometry to analyse the behaviour of Mira stars SU Cam and RY Cep, and describe how their brightness, colour, spectral type, effective temperature and Balmer emission vary over four pulsation cycles., Comment: 18 pages, 12 figures, 5 tables, accepted for publication in Journal of the AAVSO, references updated for consistency with published version
- Published
- 2021
19. WTO must ban harmful fisheries subsidies
- Author
-
Sumaila, U Rashid, Skerritt, Daniel J, Schuhbauer, Anna, Villasante, Sebastian, Cisneros-Montemayor, Andrés M, Sinan, Hussain, Burnside, Duncan, Abdallah, Patrízia Raggi, Abe, Keita, Addo, Kwasi A, Adelsheim, Julia, Adewumi, Ibukun J, Adeyemo, Olanike K, Adger, Neil, Adotey, Joshua, Advani, Sahir, Afrin, Zahidah, Aheto, Denis, Akintola, Shehu L, Akpalu, Wisdom, Alam, Lubna, Alava, Juan José, Allison, Edward H, Amon, Diva J, Anderies, John M, Anderson, Christopher M, Andrews, Evan, Angelini, Ronaldo, Anna, Zuzy, Antweiler, Werner, Arizi, Evans K, Armitage, Derek, Arthur, Robert I, Asare, Noble, Asche, Frank, Asiedu, Berchie, Asuquo, Francis, Badmus, Lanre, Bailey, Megan, Ban, Natalie, Barbier, Edward B, Barley, Shanta, Barnes, Colin, Barrett, Scott, Basurto, Xavier, Belhabib, Dyhia, Bennett, Elena, Bennett, Nathan J, Benzaken, Dominique, Blasiak, Robert, Bohorquez, John J, Bordehore, Cesar, Bornarel, Virginie, Boyd, David R, Breitburg, Denise, Brooks, Cassandra, Brotz, Lucas, Campbell, Donovan, Cannon, Sara, Cao, Ling, Cardenas Campo, Juan C, Carpenter, Steve, Carpenter, Griffin, Carson, Richard T, Carvalho, Adriana R, Castrejón, Mauricio, Caveen, Alex J, Chabi, M Nicole, Chan, Kai MA, Chapin, F Stuart, Charles, Tony, Cheung, William, Christensen, Villy, Chuku, Ernest O, Church, Trevor, Clark, Colin, Clarke, Tayler M, Cojocaru, Andreea L, Copeland, Brian, Crawford, Brian, Crépin, Anne-Sophie, Crowder, Larry B, Cury, Philippe, Cutting, Allison N, Daily, Gretchen C, Da-Rocha, Jose Maria, Das, Abhipsita, de la Puente, Santiago, de Zeeuw, Aart, Deikumah, Savior KS, Deith, Mairin, Dewitte, Boris, Doubleday, Nancy, Duarte, Carlos M, Dulvy, Nicholas K, Eddy, Tyler, Efford, Meaghan, Ehrlich, Paul R, Elsler, Laura G, and Fakoya, Kafayat A
- Subjects
General Science & Technology - Published
- 2021
20. The Unusual Eruption of the Extragalactic Classical Nova M31N 2017-09a
- Author
-
Lloyd, Christopher, Cook, Lewis M., Kiyota, Seiichiro, Tan, Hanjie, Hu, Di, Shi, Wei, Zhang, Mi, Zhang, Shenwei, Zhang, Xiaowei, Zhao, Jingyuan, Sun, Guoyou, Gao, Xing, and Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
M31N 2017-09a is a classical nova and was observed for some 160 days following its initial eruption, during which time it underwent a number of bright secondary outbursts. The light-curve is characterized by continual variation with excursions of at least 0.5 magnitudes on a daily time-scale. The lower envelope of the eruption suggests that a single power-law can describe the decline rate. The eruption is relatively long with $t_2 = 111$, and $t_3 = 153$ days., Comment: 8 pages, 3 figures
- Published
- 2020
21. Precise Measures of Orbital Period, Before and After Nova Eruption for QZ Aurigae
- Author
-
Schaefer, Bradley E., Boyd, David, Clayton, Geoffrey C., Frank, Juhan, Johnson, Christopher, Kemp, Jonathan, Pagnotta, Ashley, Patterson, Joseph O., Marco, Miguel Rodriguez, and Xiao, Limin
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
For the ordinary classical nova QZ Aurigae (which erupted in 1964), we report 1317 magnitudes from 1912--2016, including four eclipses detected on archival photographic plates from long before the eruption. We have accurate and robust measures of the orbital period both pre-eruption and post-eruption, and we find that the orbital period decreased, with a fractional change of -290.71+-0.28 parts-per-million across the eruption, with the orbit necessarily getting smaller. Further, we find that the light curve outside of eclipses and eruption is flat at near B=17.14 from 1912--1981, whereupon the average light curve starts fading down to B=17.49 with large variability. QZ Aur is a robust counter-example against the Hibernation model for the evolution of cataclysmic variables, where the model requires that all novae have their period increase across eruptions. Large period decreases across eruptions can easily arise from mass imbalances in the ejecta, as are commonly seen in asymmetric nova shells., Comment: MNRAS in press, 24 pages, 5 tables, 6 figures
- Published
- 2019
- Full Text
- View/download PDF
22. Astrovirus infects actively secreting goblet cells and alters the gut mucus barrier.
- Author
-
Cortez, Valerie, Boyd, David F, Crawford, Jeremy Chase, Sharp, Bridgett, Livingston, Brandi, Rowe, Hannah M, Davis, Amy, Alsallaq, Ramzi, Robinson, Camenzind G, Vogel, Peter, Rosch, Jason W, Margolis, Elisa, Thomas, Paul G, and Schultz-Cherry, Stacey
- Subjects
Gastrointestinal Tract ,Goblet Cells ,Epithelial Cells ,Mucus ,Animals ,Mice ,Inbred C57BL ,Escherichia coli ,Astroviridae ,Astroviridae Infections ,Virus Replication ,Virus Shedding ,Female ,Male ,Transcriptome - Abstract
Astroviruses are a global cause of pediatric diarrhea, but they are largely understudied, and it is unclear how and where they replicate in the gut. Using an in vivo model, here we report that murine astrovirus preferentially infects actively secreting small intestinal goblet cells, specialized epithelial cells that maintain the mucus barrier. Consequently, virus infection alters mucus production, leading to an increase in mucus-associated bacteria and resistance to enteropathogenic E. coli colonization. These studies establish the main target cell type and region of the gut for productive murine astrovirus infection. They further define a mechanism by which an enteric virus can regulate the mucus barrier, induce functional changes to commensal microbial communities, and alter host susceptibility to pathogenic bacteria.
- Published
- 2020
23. Soulful bodies and superflat temporalities : a nomadology of the otaku database of world history at the ends of history
- Author
-
Boyd, David John
- Subjects
777 ,B Philosophy (General) ,D History (General) ,DS Asia ,N Visual arts (General) ,PN0080 Criticism ,PN1993 Motion Pictures - Abstract
This thesis is a philosophical engagement with the popular, low, and vernacular theories of History performed and expressed within contemporary Japanese manga ('comics') and anime ('limited animation'), and most importantly, in the global production and consumption of otaku ('manga and anime fan') cultural and media ecologies. My project is rooted in a reading of the post-structural theoretical inquiries of Gilles Deleuze in parallel with what media theorist McKenzie Wark calls 'otaku philosophy' to examine how both high and low theories articulate anxieties and fascinations with the global theoretical discourses on 'the ends of History' and the imminent demise of industrial modernity. The first portion of the thesis is dedicated to a reading of the Japanese counter-cultural manga movement called gekiga ('dramatic pictures'). In traversing gekiga's post-war lineages to its revival in the medievalism of otaku artists Miura Kentarō and Yukimura Makoto, the first part postulates on what an anti-modern, anti-historical approach - or what Deleuze and Guattari call a nomadology - might look and feel like as it is mediated in the manga form. The second portion of the thesis examines the way in which Japanese anime mobilises the philosophies of nomadology in its filmic form and transmedial properties. In a critical assessment of the anime works of the otaku-founded media corporation Type-Moon, this section explores the Fate series alongside Deleuzian film and media philosophies to explore the infinite potentialities and recursive limitations of otaku nomadologies as they materialise beyond the screen. By reassessing the rise of otaku culture as a vernacular, global, and cosmopolitan rise in the critique of modernity and History, this thesis hopes to explore how transcultural and transmedial fan philosophies of historicity, memory, and temporality can be recontextualised within current academic debates about the efficacy of post-national historiographic pedagogies explored in the fields of postcolonial studies, comparative studies, global studies, and media studies.
- Published
- 2019
- Full Text
- View/download PDF
24. Photometry and spectrophotometry of the Herbig Ae star RR Tauri
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Multicolour broadband photometry and flux calibrated low resolution spectroscopy between 2014 and 2018 are used to investigate the behaviour of the highly variable Herbig Ae star RR Tauri. As the star experienced a deep Algol-like fade by a factor of over 10 in flux, we found the change in spectral continuum to be grey while H{\alpha} emission flux halved. We also observed the (V-Rc) colour index reddening as the star faded suggesting emission detectable in the Rc-band but beyond our spectral response. We confirm that the circumstellar reddening of RR Tau is consistent with an extinction ratio Rv = 5 and that its spectral type is close to A0. According to its luminosity and temperature RR Tau is located in the H-R diagram among other HAEBE stars contracting onto the Zero Age Main Sequence and has a mass between 4 and 5 MSun., Comment: 12 pages, 8 figures, accepted for publication in the Journal of the British Astronomical Association
- Published
- 2018
25. New measurements and analysis of the \b{eta} Cephei star V909 Cassiopeiae
- Author
-
Boyd, David R. S. and Koff, Robert A.
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
V909 Cas is a little-studied example of a \b{eta} Cep pulsating variable located in the OB association Cas OB8 in the Perseus spiral arm of the Milky Way. Photometric observations in 2016-7 provided 30 new times of pulsation extrema and enabled its mean pulsation period to be determined as 0.2067798(1) d. From spectroscopic observations we determined its interstellar extinction and absolute magnitude and luminosity, and located it with other \b{eta} Cep stars in the OB instability region of the H-R diagram., Comment: 8 pages, 4 figures, accepted for publication in the Journal of the British Astronomical Association
- Published
- 2018
26. SARS-CoV-2 infection results in immune responses in the respiratory tract and peripheral blood that suggest mechanisms of disease severity
- Author
-
Zhang, Wuji, Chua, Brendon Y., Selva, Kevin J., Kedzierski, Lukasz, Ashhurst, Thomas M., Haycroft, Ebene R., Shoffner-Beck, Suzanne K., Hensen, Luca, Boyd, David F., James, Fiona, Mouhtouris, Effie, Kwong, Jason C., Chua, Kyra Y. L., Drewett, George, Copaescu, Ana, Dobson, Julie E., Rowntree, Louise C., Habel, Jennifer R., Allen, Lilith F., Koay, Hui-Fern, Neil, Jessica A., Gartner, Matthew J., Lee, Christina Y., Andersson, Patiyan, Khan, Sadid F., Blakeway, Luke, Wisniewski, Jessica, McMahon, James H., Vine, Erica E., Cunningham, Anthony L., Audsley, Jennifer, Thevarajan, Irani, Seemann, Torsten, Sherry, Norelle L., Amanat, Fatima, Krammer, Florian, Londrigan, Sarah L., Wakim, Linda M., King, Nicholas J. C., Godfrey, Dale I., Mackay, Laura K., Thomas, Paul G., Nicholson, Suellen, Arnold, Kelly B., Chung, Amy W., Holmes, Natasha E., Smibert, Olivia C., Trubiano, Jason A., Gordon, Claire L., Nguyen, Thi H. O., and Kedzierska, Katherine
- Published
- 2022
- Full Text
- View/download PDF
27. Transcriptomic changes underlying EGFR inhibitor resistance in human and mouse models of basal-like breast cancer
- Author
-
Rashid, Narmeen S., Boyd, David C., Olex, Amy L., Grible, Jacqueline M., Duong, Alex K., Alzubi, Mohammad A., Altman, Julia E., Leftwich, Tess J., Valentine, Aaron D., Hairr, Nicole S., Zboril, Emily K., Smith, Jr., Timothy M., Pfefferle, Adam D., Dozmorov, Mikhail G., and Harrell, J. Chuck
- Published
- 2022
- Full Text
- View/download PDF
28. Determining the magnitudes and spectral types of the components of the binary Mira X Ophiuchi
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Several values for the magnitudes and spectral types of the components of the binary Mira X Ophiuchi have been published in the literature over the last century. Analysis of new photometry and spectroscopy of the star between 2016 May and 2016 December indicates that the V magnitude of the constant star is 9.0 and its spectral type K1III. The spectral type of the Mira changed from M6III at maximum to M7III as it faded and passed through minimum. The V magnitude of the Mira varied between 6.47 at maximum and 9.83 at minimum, a range of 3.36 magnitudes., Comment: Accepted for publication in the Journal of the British Astronomical Association, 10 pages, 8 figures
- Published
- 2017
29. Photometric and spectroscopic observations of the outburst of the symbiotic star AG Draconis between March and June 2016
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
The symbiotic star AG Dra experienced a double-peaked outburst of 0.6 magnitudes in April and May 2016. Photometry and spectroscopy through the outburst showed the B-V colour index varying linearly with the V magnitude and enabled the temperature variation of the hot star to be calculated from the changing flux in the H beta and He II 4686A emission lines., Comment: 5 pages, 4 figures
- Published
- 2016
30. A dragon’s flame of many colours: multiwavelength observations of flares from the active M binary CR Draconis
- Author
-
Jackman, James A G, primary, Shkolnik, Evgenya L, additional, Loyd, R O Parke, additional, Richey-Yowell, Tyler, additional, Llama, Joe, additional, Boyd, David, additional, Buchheim, Bob, additional, Iadevaia, David, additional, Martin, Jack, additional, Sims, Forrest, additional, Walker, Gary, additional, and Wetmore, John, additional
- Published
- 2024
- Full Text
- View/download PDF
31. Correlating Stability-Indicating Biochemical and Biophysical Characteristics with In Vitro Cell Potency in mRNA LNP Vaccine
- Author
-
Tong, Xin, primary, Raffaele, Jessica, additional, Feller, Katrina, additional, Dornadula, Geethanjali, additional, Devlin, James, additional, Boyd, David, additional, Loughney, John W., additional, Shanter, Jon, additional, and Rustandi, Richard R., additional
- Published
- 2024
- Full Text
- View/download PDF
32. Changes in the spectrum of Z Ursae Majoris during its rise through a maximum in June 2014
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
The semiregular variable Z UMa experienced a particularly deep minimum at the end of March 2014 followed by a three month rise to maximum. The rise and subsequent decline were followed with low resolution (R~1000) spectroscopy, possibly for the first time. The spectral type of Z UMa varied between M7III at minimum and M4III at maximum while the bright hydrogen emission lines reported by observers during the last century now appear relatively weak and transitory., Comment: 5 pages, 3 figures
- Published
- 2015
33. Results of a campaign to observe outbursts of the dwarf nova CSS 121005:212625+201948
- Author
-
Shears, Jeremy, Boardman, James, Boyd, David, Buczynski, Denis, Dubovsky, Pavol, Carballo, Juan-Luis Gonzalez, Menzies, Kenneth, Miller, Ian, Pickard, Roger, Poyner, Gary, Sabo, Richard, and Sargent, Richard
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
A monitoring programme of CSS 121005:212625+201948 covering nearly two observing seasons has shown that it is a typical SU UMa dwarf nova, but it has one of the shortest supercycles of its class, at 66.9(6) d. The superoutbursts are interspersed with 3 to 7 short duration (~2 days) normal outbursts each of which are separated by a mean interval of 11 days, but can be as short as 2 days. The most intensively studied superoutburst was that of 2014 November, which lasted 14 days and had an outburst amplitude of >4.8 magnitudes, reaching magnitude 15.7 at its brightest. Time resolved photometry revealed superhumps with a peak-to-peak amplitude of 0.2 magnitudes, later declining to 0.1 magnitude. The superhump period was Psh = 0.08838(18) d. Time resolved photometry was conducted during several other superoutbursts, which gave broadly similar results., Comment: 21 pages, 8 figures. Accepted for publication in the Journal of the British Astronomical Association
- Published
- 2015
34. Faint-state transitions in the SW Sextantis nova-like variable, HS 0455+8315
- Author
-
Shears, Jeremy, Gaensicke, Boris, Rodriguez-Gil, Pablo, Boyd, David, Darlington, Graham, and Miller, Ian
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We present the fourteen year-long light curve of the SW Sextantis nova-like variable, HS 0455+8315, from 2000 November to 2015 February which reveals two deep faint states at magnitude 19 - 20, each of which lasted about 500 and 540 days. Outside these faint states, the star spent most of the time in a normal state at a magnitude of about 15.3. The second faint state was the better observed of the two and was found to have a linear decline of 0.009 mag/day, which was soon followed by a more rapid brightening at -0.020 mag/day. Time series photometry during both the normal state and near minimum light at about magnitude 18 showed that the eclipses had very similar profiles and that outside the eclipse there were irregular modulations typical of the flickering inherent to accreting CVs. Our photometry leading up to the minimum shows that accretion was still ongoing during this time., Comment: 13 pages, 5 figures. Accepted for publication in the Journal of the British Astronomical Association
- Published
- 2015
35. Photometric and spectroscopic observations of the 2014 eclipse of the complex binary EE Cephei
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We report photometric and spectroscopic observations of the 2014 eclipse of EE Cep. This proved to be one of the shallower eclipses on record rather than one of the deepest as predicted. The general shape of the eclipse light curve was similar to that of the 2003 eclipse. The spectral type before and after eclipse was consistent with B5III and became slightly later at mid-eclipse. Total flux in the H{\alpha} emission line remained relatively constant through the eclipse., Comment: 7 pages, 4 figures, submitted to the Journal of the British Astronomical Association
- Published
- 2014
36. HW Bootis: an enigmatic cataclysmic variable star
- Author
-
Shears, Jeremy, Boyd, David, Darlington, Graham, Miller, Ian, Pickard, Roger, Poyner, Gary, Sabo, Richard, Simonsen, Mike, and Stein, William
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We present the 13-year light curve of HW Boo between 2001 May and 2014 May. We identified 12 outbursts, which typically lasted 2 to 5 days, with an amplitude of 2.7 to 3.6 magnitudes. Time resolved photometry during two outbursts revealed small hump-like structures which increased in size as the outburst progressed, reaching a peak-to-peak amplitude of ~0.8 mag. They occurred on timescales of 15 min to an hour, but did not exhibit a stable period. Similar irregular hump-like variations of 0.1 to 0.8 magnitudes, at intervals of 7 to 30 minutes, were also detected during quiescence. We discuss whether HW Boo might be a dwarf nova of the SU UMa family or an Intermediate Polar, but require further observations to support classification., Comment: 14 pages, 5 Figures. Accepted for publication in the Journal of the British Astronomical Association
- Published
- 2014
37. Why you should vote in the ballot
- Author
-
Cruickshanks-Boyd, David
- Published
- 2015
38. Influenza Virus Z-RNAs Induce ZBP1-Mediated Necroptosis
- Author
-
Zhang, Ting, Yin, Chaoran, Boyd, David F., Quarato, Giovanni, Ingram, Justin P., Shubina, Maria, Ragan, Katherine B., Ishizuka, Takumi, Crawford, Jeremy Chase, Tummers, Bart, Rodriguez, Diego A., Xue, Jia, Peri, Suraj, Kaiser, William J., López, Carolina B., Xu, Yan, Upton, Jason W., Thomas, Paul G., Green, Douglas R., and Balachandran, Siddharth
- Published
- 2020
- Full Text
- View/download PDF
39. Exuberant fibroblast activity compromises lung function via ADAMTS4
- Author
-
Boyd, David F., Allen, E. Kaitlynn, Randolph, Adrienne G., Guo, Xi-zhi J., Weng, Yunceng, Sanders, Catherine J., and Bajracharya, Resha
- Subjects
Proteases -- Analysis ,Fibroblasts -- Mechanical properties ,Extracellular matrix -- Models ,Pulmonary function tests -- Analysis ,Environmental issues ,Science and technology ,Zoology and wildlife conservation - Abstract
Severe respiratory infections can result in acute respiratory distress syndrome (ARDS).sup.1. There are no effective pharmacological therapies that have been shown to improve outcomes for patients with ARDS. Although the host inflammatory response limits spread of and eventually clears the pathogen, immunopathology is a major contributor to tissue damage and ARDS.sup.1,2. Here we demonstrate that respiratory viral infection induces distinct fibroblast activation states, which we term extracellular matrix (ECM)-synthesizing, damage-responsive and interferon-responsive states. We provide evidence that excess activity of damage-responsive lung fibroblasts drives lethal immunopathology during severe influenza virus infection. By producing ECM-remodelling enzymes--in particular the ECM protease ADAMTS4--and inflammatory cytokines, damage-responsive fibroblasts modify the lung microenvironment to promote robust immune cell infiltration at the expense of lung function. In three cohorts of human participants, the levels of ADAMTS4 in the lower respiratory tract were associated with the severity of infection with seasonal or avian influenza virus. A therapeutic agent that targets the ECM protease activity of damage-responsive lung fibroblasts could provide a promising approach to preserving lung function and improving clinical outcomes following severe respiratory infections. Viral infection of the respiratory system induces exuberant fibroblast activity, resulting in extensive remodelling of the extracellular matrix and cytokine release, which promote immune cell infiltration of the affected area at the expense of respiratory function., Author(s): David F. Boyd [sup.1] , E. Kaitlynn Allen [sup.1] , Adrienne G. Randolph [sup.2] [sup.3] , Xi-zhi J. Guo [sup.1] , Yunceng Weng [sup.4] , Catherine J. Sanders [sup.1] [...]
- Published
- 2020
- Full Text
- View/download PDF
40. Spectroscopic observations of the bright RV Tauri variable R Scuti
- Author
-
Boyd, David
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
A series of spectra of the RV Tauri star R Scuti taken as it rose from a deep minimum to a bright maximum during 2013 October and November reveals major changes taking place in the photosphere and outer atmosphere of the star. This may be the first such series of spectra and demonstrates the capability of amateur spectroscopy for studying these complex stars., Comment: 3 pages, 5 figures
- Published
- 2014
41. Periodic Variations in the Residual Eclipse Flux and Eclipse Timings of Asynchronous Polar V1432 Aql: Evidence of a Shifting Threading Region
- Author
-
Littlefield, Colin, Mukai, Koji, Cain, Ryan, Mumme, Raymond, Magno, Katrina C., Corpuz, Taylor, Sandefur, Davis, Boyd, David, Cook, Michael, Ulowetz, Joseph, and Martinez, Luis
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We report the results of a twenty-eight-month photometric campaign studying V1432 Aql, the only known eclipsing, asynchronous polar. Our data show that both the residual eclipse flux and eclipse O-C timings vary strongly as a function of the spin-orbit beat period. Relying upon a new model of the system, we show that cyclical changes in the location of the threading region along the ballistic trajectory of the accretion stream could produce both effects. This model predicts that the threading radius is variable, in contrast to previous studies which have assumed a constant threading radius. Additionally, we identify a very strong photometric maximum which is only visible for half of the beat cycle. The exact cause of this maximum is unclear, but we consider the possibility that it is the optical counterpart of the third accreting polecap proposed by Rana et al. (2005). Finally, the rate of change of the white dwarf's spin period is consistent with it being proportional to the difference between the spin and orbital periods, implying that the spin period is approaching the orbital period asymptotically., Comment: 28 pages, 9 figures; label on Y-axis in Fig. 2 has been corrected (was incorrect in 1408.4207v1)
- Published
- 2014
42. The asynchronous polar V1432 Aquilae and its path back to synchronism
- Author
-
Boyd, David, Patterson, Joseph, Allen, William, Bolt, Greg, Bonnardeau, Michel, Tut, Campbell, Jeannie, Cejudo, David, Cook, Michael, de Miguel, Enrique, Ding, Claire, Dvorak, Shawn, Foote, Jerrold, Fried, Robert, Hambsch, Franz-Josef, Kemp, Jonathan, Krajci, Thomas, Monard, Berto, Ogmen, Yenal, Rea, Robert, Roberts, George, Skillman, David, Starkey, Donn, Ulowetz, Joseph, Uthas, Helena, and Walker, Stan
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
V1432 Aquilae is the only known eclipsing asynchronous polar. In this respect it is unique and therefore merits our attention. We report the results of a 15-year campaign by the globally distributed Center for Backyard Astrophysics to observe V1432 Aql and investigate its return to synchronism. Originally knocked out of synchrony by a nova explosion before observing records began, the magnetic white dwarf in V1432 Aql is currently rotating slower than the orbital period but is gradually catching up. The fortuitously high inclination of the binary orbit affords us the bonus of eclipses providing a regular clock against which these temporal changes can be assessed. At the present rate, synchronism should be achieved around 2100. The continually changing trajectory of the accretion stream as it follows the magnetic field lines of the rotating white dwarf produces a complex pattern of light emission which we have measured and documented, providing comprehensive observational evidence against which physical models of the system can be tested., Comment: 14 pages, 16 figures, presented at the Society for Astronomical Sciences 33rd Annual Symposium on Telescope Science, June 2014, acknowledgements added
- Published
- 2014
43. Squarefree values of trinomial discriminants
- Author
-
Boyd, David W., Martin, Greg, and Thom, Mark
- Subjects
Mathematics - Number Theory - Abstract
The discriminant of a trinomial of the form $x^n \pm x^m \pm 1$ has the form $\pm n^n \pm (n-m)^{n-m} m^m$ if $n$ and $m$ are relatively prime. We investigate when these discriminants have nontrivial square factors. We explain various unlikely-seeming parametric families of square factors of these discriminant values: for example, when $n$ is congruent to 2 (mod 6) we have that $((n^2-n+1)/3)^2$ always divides $n^n - (n-1)^{n-1}$. In addition, we discover many other square factors of these discriminants that do not fit into these parametric families. The set of primes whose squares can divide these sporadic values as $n$ varies seems to be independent of $m$, and this set can be seen as a generalization of the Wieferich primes, those primes $p$ such that $2^{p-1}$ is congruent to 1 (mod $p^2$). We provide heuristics for the density of squarefree values of these discriminants and the density of these "sporadic" primes., Comment: 22 pages, 1 table. Minor revisions from version 1, including three new references
- Published
- 2014
- Full Text
- View/download PDF
44. Z Cam Stars in the Twenty-First Century
- Author
-
Simonsen, Mike, Boyd, David, Goff, Bill, Krajci, Tom, Menzies, Kenneth, Otero, Sebastian, Padovan, Stefano, Poyner, Gary, Roe, James, Sabo, Richard, Sjoberg, George, Staels, Bart, Stubbings, Rod, Toone, John, and Wils, Patrick
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Z Cam stars are a small subset of dwarf novae that exhibit standstills in their light curves. Most modern literature and catalogs of cataclysmic variables quote the number of known Z Cams to be on the order of 30 or so systems. After a four-year observing campaign and an exhaustive examination of the data in the AAVSO International Database we have trimmed that number by a third. One of the reasons for the misclassification of some systems is the fact that the definition of what a Z Cam is has changed over the last 85 years to what it is today. This has caused many stars formerly assumed to be Z Cams or rumored to be Z Cams to be eliminated from the final list. In this paper we present the results of our investigation into 65 stars listed at one time or another in the literature as Z Cams or possible Z Cams., Comment: 22 pages, 26 figures, 3 tables, accepted for publication in the Journal of the AAVSO
- Published
- 2014
45. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. V: The Fifth Year (2012-2013)
- Author
-
Kato, Taichi, Hambsch, Franz-Josef, Maehara, Hiroyuki, Masi, Gianluca, Nocentini, Francesca, Dubovsky, Pavol A., Kudzej, Igor, Imamura, Kazuyoshi, Ogi, Minako, Tanabe, Kenji, Akazawa, Hidehiko, Krajci, Thomas, Miller, Ian, de Miguel, Enrique, Henden, Arne, Littlefield, Colin, Noguchi, Ryo, Ishibashi, Takehiro, Ono, Rikako, Kawabata, Miho, Kobayashi, Hiroshi, Sakai, Daisuke, Nishino, Hirochika, Furukawa, Hisami, Masumoto, Kazunari, Matsumoto, Katsura, Ohshima, Tomohito, Nakata, Chikako, Honda, Satoshi, Kinugasa, Kenzo, Hashimoto, Osamu, Stein, William, Pickard, Roger D., Kiyota, Seiichiro, Pavlenko, Elena P., Antonyuk, Oksana I., Baklanov, Aleksei V., Antonyuk, Kirill, Samsonov, Denis, Pit, Nikolaj, Sosnovskij, Aleksei, Oksanen, Arto, Harlingten, Caisey, Tyyska, Jenni, Monard, Berto, Shugarov, Sergey Yu., Chochol, Drahomir, Kasai, Kiyoshi, Maeda, Yutaka, Hirosawa, Kenji, Itoh, Hiroshi, Sabo, Richard, Ulowetz, Joseph, Morelle, Etienne, Michel, Raul, Suarez, Genaro, James, Nick, Dvorak, Shawn, Voloshina, Irina B., Richmond, Michael, Staels, Bart, Boyd, David, Andreev, Maksim V., Parakhin, Nikolai, Katysheva, Natalia, Miyashita, Atsushi, Nakajima, Kazuhiro, Bolt, Greg, Padovan, Stefano, Nelson, Peter, Starkey, Donn R., Buczynski, Denis, Starr, Peter, Goff, William N., Denisenko, Denis, Kochanek, Christopher S., Shappee, Benjamin, Stanek, Krzysztof Z., Prieto, Jose L., Itagaki, Koh-ichi, Kaneko, Shizuo, Stubbings, Rod, Muyllaert, Eddy, Shears, Jeremy, Schmeer, Patrick, Poyner, Gary, and Marco, Miguel Rodriguez
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Continuing the project described by Kato et al. (2009a, arXiv:0905.1757), we collected times of superhump maxima for SU UMa-type dwarf novae mainly observed during the 2012-2013 season. We found three objects (V444 Peg, CSS J203937 and MASTER J212624) having strongly positive period derivatives despite the long orbital period (Porb). By using the period of growing stage (stage A) superhumps, we obtained mass ratios for six objects. We characterized nine new WZ Sge-type dwarf novae. We made a pilot survey of the decline rate of slowly fading part of SU UMa-type and WZ Sge-type outbursts. The decline time scale was found to generally follow the expected Porb^(1/4) dependence and WZ Sge-type outbursts also generally follow this trend. There are some objects which show slower decline rates, and we consider these objects good candidates for period bouncers. We also studied unusual behavior in some objects, including BK Lyn which made a transition from an ER UMa-type state to the novalike (standstill) state in 2013 and unusually frequent occurrence of superoutbursts in NY Ser and CR Boo. We applied least absolute shrinkage and selection operator (Lasso) power spectral analysis, which has been proven to be very effective in analyzing the Kepler data, to ground-based photometry of BK Lyn and detected the dramatic disappearance of the signal of negative superhumps in 2013. We suggested that the mass-transfer rates did not vary strongly between the ER UMa-type state and novalike state in BK Lyn, and this transition was less likely caused by a systematic variation of the mass-transfer rate., Comment: 83 pages, 95 figures, accepted for publication in PASJ
- Published
- 2013
- Full Text
- View/download PDF
46. Dodging Dysfunctional Dynamics in Power Exchange
- Author
-
Boyd, David P.
- Abstract
In today's organizations, the impetus for employee empowerment remains strong. By developing an internal talent base, companies increase the likelihood of comprehensive contributions and also engender loyalty within the ranks. A proclivity for power dispersion is evident among many pundits, with some even decreeing it an ethical mandate. Yet, if rashly executed, empowerment can result in dire outcomes for the individual and dysfunctional consequences for the firm. Through reference to the medium of film, this paper portrays four situations where empowerment efforts have gone awry, accentuating employee estrangement and eroding corporate ethics. Because the behavioral dynamics of film are frozen in time and thus susceptible to recursive scrutiny, students can glean institutional insights that will facilitate career advancement. Just as important, they will confront value conflicts that impel them to clarify their own ethical stance.
- Published
- 2010
47. A Primer for Accounting Certification: Complete Analysis of the Process with Listing of Sources
- Author
-
Boyd, David T., Boyd, Sanithia C., and Berry, Priscilla
- Abstract
As a result of globalization and the growth and complexity of both domestic and international bodies requiring accountants, the need for highly sophisticated training and specific certification is mandatory. Students seeking career positions in the field of accounting are amazingly left without the easy access to certification that one might think would be readily available. Interest in, and the quest for, certification is domestic and international and across all study fields. To be fully prepared a well-equipped accountant today will be cross functional and have "proof" of his/her knowledge in the form of certifications in other fields as well as being multi-national by holding certifications issued in countries where he/she practices or travels. Currently, because the field is being transformed so rapidly by world events and the economy, students, as well as practitioners, need more easily accessible information on what certifications are available and how to achieve them. This document identifies and reviews accounting requirements and major certifications in accounting, finance, and information technology, including the recently developed fields of fraud and forensic accounting. Basic access information is provided for each requirement and certification and web addresses for additional data relating to qualification and certification are included.
- Published
- 2009
48. Cinematic Perspectives on Organizational Mentoring
- Author
-
Boyd, David P.
- Abstract
Properly conceived and conducted, organizational mentoring can bestow benefits on the suppliant, the mentor and the firm. If prospective protégés assess the context of a mentoring relationship before they enter into one, they can enjoy a bonding experience that facilitates psychological satisfaction and furthers professional advancement. The movie medium is an educative means of appreciating and attaining these positive outcomes. The instructive lens of drama can complement traditional curricular materials in courses on behavioral dynamics. Over the past seven years, the author has assigned a film project in his Leadership classes at the undergraduate and MBA level. Of the 120 films chosen for students projects, five compellingly capture functional and dysfunctional aspects of protégé-protector linkages. After analyzing these films, the paper proposes ten precepts that will enhance the mentoring experience for workplace aspirants.
- Published
- 2009
49. BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution
- Author
-
Patterson, Joseph, Uthas, Helena, Kemp, Jonathan, de Miguel, Enrique, Krajci, Thomas, Foote, Jerry, Hambsch, Franz-Josef, Campbell, Tut, Roberts, George, Cejudo, David, Dvorak, Shawn, Vanmunster, Tonny, Koff, Robert, Skillman, David, Harvey, David, Martin, Brian, Rock, John, Boyd, David, Oksanen, Arto, Morelle, Etienne, Ulowetz, Joseph, Kroes, Anthony, Sabo, Richard, and Jensen, Lasse
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
We summarize the results of a 20-year campaign to study the light curves of BK Lyncis, a nova-like star strangely located below the 2-3 hour orbital period gap in the family of cataclysmic variables. Two apparent "superhumps" dominate the nightly light curves - with periods 4.6% longer, and 3.0% shorter, than P_orb. The first appears to be associated with the star's brighter states (V~14), while the second appears to be present throughout and becomes very dominant in the low state (V~15.7). Starting in the year 2005, the star's light curve became indistinguishable from that of a dwarf nova - in particular, that of the ER UMa subclass. Reviewing all the star's oddities, we speculate: (a) BK Lyn is the remnant of the probable nova on 30 December 101, and (b) it has been fading ever since, but has taken ~2000 years for the accretion rate to drop sufficiently to permit dwarf-nova eruptions. If such behavior is common, it can explain other puzzles of CV evolution. One: why the ER UMa class even exists (because all members can be remnants of recent novae). Two: why ER UMa stars and short-period novalikes are rare (because their lifetimes, which are essentially cooling times, are short). Three: why short-period novae all decline to luminosity states far above their true quiescence (because they're just getting started in their postnova cooling). Four: why the orbital periods, accretion rates, and white-dwarf temperatures of short-period CVs are somewhat too large to arise purely from the effects of gravitational radiation (because the unexpectedly long interval of enhanced postnova brightness boosts the mean mass-transfer rate). These are substantial rewards in return for one investment of hypothesis: that the second parameter in CV evolution, besides P_orb, is time since the last classical-nova eruption., Comment: PDF, 46 pages, 4 tables, 10 figures; in preparation; more info at http://cbastro.org/
- Published
- 2012
- Full Text
- View/download PDF
50. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. IV: The Fourth Year (2011-2012)
- Author
-
Kato, Taichi, Hambsch, Franz-Josef, Maehara, Hiroyuki, Masi, Gianluca, Miller, Ian, Noguchi, Ryo, Akasaka, Chihiro, Aoki, Tomoya, Kobayashi, Hiroshi, Matsumoto, Katsura, Nakagawa, Shinichi, Nakazato, Takuma, Nomoto, Takashi, Ogura, Kazuyuki, Ono, Rikako, Taniuchi, Keisuke, Stein, William, Henden, Arne, de Miguel, Enrique, Kiyota, Seiichiro, Dubovsky, Pavol A., Kudzej, Igor, Imamura, Kazuyoshi, Akazawa, Hidehiko, Takagi, Ryosuke, Wakabayashi, Yuya, Ogi, Minako, Tanabe, Kenji, Ulowetz, Joseph, Morelle, Etienne, Pickard, Roger D., Ohshima, Tomohito, Kasai, Kiyoshi, Pavlenko, Elena P., Antonyuk, Oksana I., Baklanov, Aleksei V., Antonyuk, Kirill, Samsonov, Denis, Pit, Nikolaj, Sosnovskij, Aleksei, Littlefield, Colin, Sabo, Richard, Ruiz, Javier, Krajci, Thomas, Dvorak, Shawn, Oksanen, Arto, Hirosawa, Kenji, Goff, William N., Monard, Berto, Shears, Jeremy, Boyd, David, Voloshina, Irina B., Shugarov, Sergey Yu., Chochol, Drahomir, Miyashita, Atsushi, Pietz, Jochen, Katysheva, Natalia, Itoh, Hiroshi, Bolt, Greg, Andreev, Maksim V., Parakhin, Nikolai, Malanushenko, Viktor, Martinelli, Fabio, Denisenko, Denis, Stockdale, Chris, Starr, Peter, Simonsen, Mike, Tristram, Paul. J., Fukui, Akihiko, Tordai, Tamas, Fidrich, Robert, Paxson, Kevin B., Itagaki, Koh-ichi, Nakashima, Youichirou, Yoshida, Seiichi, Nishimura, Hideo, Kryachko, Timur V., Samokhvalov, Andrey V., Korotkiy, Stanislav A., Satovski, Boris L., Stubbings, Rod, Poyner, Gary, Muyllaert, Eddy, Gerke, Vladimir, MacDonald II, Walter, Linnolt, Michael, Maeda, Yutaka, and Hautecler, Hubert
- Subjects
Astrophysics - Solar and Stellar Astrophysics - Abstract
Continuing the project described by Kato et al. (2009, arXiv:0905.1757), we studied 86 SU UMa-type dwarf novae. We confirmed the general trends such as the relation between period derivatives and orbital periods. There are some systems showing positive period derivatives despite the long orbital periods. We observed the 2011 outburst of the WZ Sge-type dwarf nova BW Scl, and recorded an O-C diagram similar to those of previously known WZ Sge-type dwarf novae. The WZ Sge-type dwarf nova OT J184228.1+483742 showed an unusual pattern of double outbursts composed of an outburst with early superhumps and one with ordinary superhumps. We propose an interpretation that a very small growth rate of the 3:1 resonance due to an extremely low mass-ratio led to a quenching of the superoutburst before the ordinary superhumps appeared. We studied ER UMa-type dwarf novae and found that V1159 Ori showed positive superhumps similar to ER UMa in the 1990s. The recently recognized ER UMa-type object BK Lyn dominantly showed negative superhumps, and its behavior was very similar to the present-day state of ER UMa. The pattern of period variations in AM CVn-type objects were very similar to short-period hydrogen-rich SU UMa-type dwarf novae, making them helium analogue of hydrogen-rich SU UMa-type dwarf novae. SBS 1108+574, a peculiar hydrogen-rich dwarf nova below the period minimum, showed a very similar pattern of period variations to those of short-period SU UMa-type dwarf novae. The mass-ratio derived from the detected orbital period suggests that this secondary is a somewhat evolved star whose hydrogen envelope was mostly stripped during the mass-exchange. CC Scl, MASTER OT J072948.66+593824.4 and OT J173516.9+154708 showed only low-amplitude superhumps with complex profiles. These superhumps are likely a combination of closely separated two periods., Comment: 81 pages, 92 figures, PASJ in press, correction in the author list and text
- Published
- 2012
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.