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43 results on '"Young, Timothy R."'

2. Peculiar Type II Supernovae from Blue Supergiants

Author

Kleiser, Io K. W., Poznanski, Dovi, Kasen, Daniel, Young, Timothy R., Chornock, Ryan, Filippenko, Alexei V., Challis, Peter, Ganeshalingam, Mohan, Kirshner, Robert P., Li, Weidong, Matheson, Thomas, Nugent, Peter E., and Silverman, Jeffrey M.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics
Abstract

The vast majority of Type II supernovae (SNe) are produced by red supergiants (RSGs), but SN 1987A revealed that blue supergiants (BSGs) can produce members of this class as well, albeit with some peculiar properties. This best studied event revolutionized our understanding of SNe, and linking it to the bulk of Type II events is essential. We present here optical photometry and spectroscopy gathered for SN 2000cb, which is clearly not a standard Type II SN and yet is not a SN 1987A analog. The light curve of SN 2000cb is reminiscent of that of SN 1987A in shape, with a slow rise to a late optical peak, but on substantially different time scales. Spectroscopically, SN 2000cb resembles a normal SN II but with ejecta velocities that far exceed those measured for SN 1987A or normal SNe II, above 18000 km/s for H-alpha at early times. The red colours, high velocities, late photometric peak, and our modeling of this object all point toward a scenario involving the high-energy explosion of a small-radius star, most likely a BSG, producing 0.1 solar masses of Ni-56. Adding a similar object to the sample, SN 2005ci, we derive a rate of about 2% of the core-collapse rate for this loosely defined class of BSG explosions., Comment: Accepted to MNRAS on March 14, 2011

Published
2011
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3. Hydrogen in Type Ic Supernovae?

Author

Branch, David, Jeffery, David J., Young, Timothy R., and Baron, E.

Subjects
Astrophysics
Abstract

By definition, a Type Ic supernova (SN Ic) does not have conspicuous lines of hydrogen or helium in its optical spectrum. SNe Ic usually are modelled in terms of the gravitational collapse of bare carbon-oxygen cores. We consider the possibility that the spectra of ordinary (SN 1994I-like) SNe Ic have been misinterpreted, and that SNe Ic eject hydrogen. An absorption feature usually attributed to a blend of Si II 6355 and C II 6580 may be produced by H-alpha. If SN 1994I-like SNe Ic eject hydrogen, the possibility that hypernova (SN 1998bw-like) SNe Ic, some of which are associated with gamma-ray bursts, also eject hydrogen should be considered. The implications of hydrogen for SN Ic progenitors and explosion models are briefly discussed., Comment: Accepted by PASP. Several significant changes including one additional figure

Published
2006
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4. A Parameter Study of Type II Supernova Light Curves Using 6 M_odot He Cores

Author

Young, Timothy R.

Subjects
Astrophysics
Abstract

Results of numerical calculations of Type II supernova light curves are presented. The model progenitor stars have 6 $M{_\odot}$ cores and various envelopes, originating from a numerically evolved 20 $M{_\odot}$ star. Five parameters that affect the light curves are examined: the ejected mass, the progenitor radius, the explosion energy, the $^{56}$Ni mass, and the extent of $^{56}$Ni mixing. The following affects have been found: 1) the larger the progenitor radius the brighter the early--time light curve, with little affect on the late--time light curve, 2) the larger the envelope mass the fainter the early light curve and the flatter the slope of the late light curve, 3) the larger the explosion energy the brighter the early light curve and the steeper the slope of the late light curve, 4) the larger the $^{56}$Ni mass the brighter the overall light curve after 20 to 50 days, with no affect on the early light curve, 5) the more extensive the $^{56}$Ni mixing the brighter the early light curve and the steeper the late light curve. The primary parameters affecting the light curve shape are the progenitor radius and the ejected mass. The secondary parameters are the explosion energy, $^{56}$Ni mass and $^{56}$Ni mixing. I find that while in principle the general shape and absolute magnitude of a light curve indicate a unique set of parameters, in practice it is difficult to avoid some ambiguity in the parameters. I find that the nickel--powered diffusion wave and the recombination of helium produce a prominent secondary peak in all our calculations. The feature is less prominent when compositional mixing, both $^{56}$Ni mixing and mixing between the hydrogen and helium layers, occurs. The model photospheric temperatures and velocities are presented, for comparison to observation., Comment: 39 pages, 15 figures. Astrophysical Journal (Accepted, Dec. 20, 2004)

Published
2004
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6. Comprehensive literature review on the radiographic findings, imaging modalities, and the role of radiology in the COVID-19 pandemic

Author

Pal, Aman, primary, Ali, Abulhassan, additional, Young, Timothy R, additional, Oostenbrink, Juan, additional, Prabhakar, Akul, additional, Prabhakar, Amogh, additional, Deacon, Nina, additional, Arnold, Amar, additional, Eltayeb, Ahmed, additional, Yap, Charles, additional, Young, David M, additional, Tang, Alan, additional, Lakshmanan, Subramanian, additional, Lim, Ying Yi, additional, Pokarowski, Martha, additional, and Kakodkar, Pramath, additional

Published
2021
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7. LETTERS

Author

Waters, Elwood L., Stam, Paul N., Michaels, Mariann, Young, Timothy R., Steiner, Alison, Angelucci, Marc, Rooney, John P., Beatty, Georgia A., Protokowicz, Stan, and Goetzinger, Patrick G.

Published
2000

11. Peculiar Type II supernovae from blue supergiants

Author

Kleiser, Io K. W., primary, Poznanski, Dovi, additional, Kasen, Daniel, additional, Young, Timothy R., additional, Chornock, Ryan, additional, Filippenko, Alexei V., additional, Challis, Peter, additional, Ganeshalingam, Mohan, additional, Kirshner, Robert P., additional, Li, Weidong, additional, Matheson, Thomas, additional, Nugent, Peter E., additional, and Silverman, Jeffrey M., additional

Published
2011
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17. Identification of T Cell-Restricted Genes, and Signatures for Different T Cell Responses, Using a Comprehensive Collection of Microarray Datasets

Author

Chtanova, Tatyana, primary, Newton, Rebecca, additional, Liu, Sue M., additional, Weininger, Lilach, additional, Young, Timothy R., additional, Silva, Diego G., additional, Bertoni, Francesco, additional, Rinaldi, Andrea, additional, Chappaz, Stephane, additional, Sallusto, Federica, additional, Rolph, Michael S., additional, and Mackay, Charles R., additional

Published
2005
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28. Instabilities and Mixing in SN 1993J

Author

Iwamoto, Kohichi, primary, Young, Timothy R., additional, Nakasato, Naohito, additional, Shigeyama, Toshikazu, additional, Nomoto, Ken'ichi, additional, Hachisu, Izumi, additional, and Saio, Hideyuki, additional

Published
1997
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32. Ten-m2 Is Required for the Generation of Binocular Visual Circuits.

Author

Young, Timothy R., Bourke, Michael, Xiaohong Zhou, Oohashi, Toshitaka, Sawatari, Atomu, Fässler, Reinhard, and Leamey, Catherine A.

Subjects
*BINOCULAR vision, *RETINA, *LABORATORY mice, *GENICULATE bodies, *IMMUNOHISTOCHEMISTRY
Abstract

Functional binocular vision requires that inputs arising from the two retinae are integrated and precisely organized within central visual areas. Previous studies have demonstrated an important role for one member of the Ten-m/Odz/teneurin family, Ten-m3, in the mapping of ipsilateral retinal projections. Here, we have identified a distinct role for another closely related family member, Ten-m2, in the formation of the ipsilateral projection in the mouse visual system. Ten-m2 expression was observed in the retina, dorsal lateral geniculate nucleus (dLGN), superior colliculus (SC), and primary visual cortex (VI) of the developing mouse. Anterograde and retrograde tracing experiments in Ten-m2 knock-out (KO) mice revealed a specific decrease in ipsilateral retinal ganglion cells projecting to dLGN and SC. This reduction was most prominent in regions corresponding to ventral retina. No change in the topography of ipsilateral or contralateral projections was observed. While expression of a critical ipsilateral fate determinant, Zic2, appeared unaltered, a notable reduction in one of its downstream targets, EphBl, was observed in ventral retina, suggesting that Ten-m2 may interact with this molecular pathway. Immunohistochemistry for c-fos, a neural activity marker, revealed that the area of VI driven by ipsilateral inputs was reduced in KOs, while the ratio of ipsilateral-to-contralateral responses contributing to binocular activation during visually evoked potential recordings was also diminished. Finally, a novel two-alternative swim task revealed specific deficits associated with dorsal visual field. These data demonstrate a requirement for Ten-m2 in the establishment of ipsilateral projections, and thus the generation of binocular circuits, critical for mammalian visual function. [ABSTRACT FROM AUTHOR]

Published
2013
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37. Presentation of Gamma-Irradiated-in-Air Polyethylene Wear in the Form of a Synovial Cyst.

Author

Edwards, Bryan T., Leach, Patrick B., Zura, Robert, Scott Corpe, R., and Young, Timothy R.

Subjects
SYNOVITIS, POLYETHYLENE, TOTAL knee replacement, KNEE surgery, ARTHROPLASTY, CYSTS (Pathology), STERILIZATION (Disinfection), SYNOVIAL membrane diseases
Abstract

The increased wear of polyethylene sterilized with gamma irradiation in air has well been documented in the total knee arthroplasty literature. Our case report describes a patient with a well-functioning total knee replacement presenting with wear debris synovitis in the form of a large synovial cyst. We discuss this patient's preoperative evaluation, intraoperative findings, and postoperative outcome after synovectomy and polyethylene exchange. We also review the current literature on appropriate polyethylene sterilization methods. [ABSTRACT FROM AUTHOR]

Published
2003
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40. The effects of state regulation on the use of DSM resources by electric utilities

Author

Schweitzer, Martin and Young, Timothy R.

Abstract

Support from regulators, coming in a variety of forms, has led to substantial utility efforts to secure demand-side management cost and energy savings, but without continued regulatory support these utility efforts could fall off sharply. Regulators that wish to continue to promote cost-effective DSM must understand the changing dynamics of the new competitive industry and the factors that will influence utility actions.

Published
1995
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41. Supernova 1909A: a precedent for SN1987A?

Author

Branch, David and Young, Timothy R.

Subjects
Supernovae -- Research, Astronomical research -- Analysis, Environmental issues, Science and technology, Zoology and wildlife conservation
Published
1988

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