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Search Results: 1 - 10 of 195196 matches for " Joel D. Offenberg "
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Ultraviolet Signatures of Tidal Interaction in the Giant Spiral Galaxy, M101
William H. Waller,Ralph C. Bohlin,Robert H. Cornett,Michael N. Fanelli,Wendy L. Freedman,Jesse K. Hill,Barry F. Madore,Susan G. Neff,Joel D. Offenberg,Robert W. O'Connell,Morton S. Roberts,Andrew M. Smith,Theodore P. Stecher
Physics , 1996, DOI: 10.1086/304057
Abstract: We present new evidence for tidal interactions having occurred in the disk of M101 in the last 10^8 - 10^9 years. Recent imaging of the far-ultraviolet emission from M101 by the Shuttle-borne Ultraviolet Imaging Telescope (UIT) reveals with unprecedented clarity a disk-wide pattern of multiple linear arm segments (``crooked arms''). The deep FUV image also shows a faint outer spiral arm with a (``curly tail'') feature that appears to loop around the supergiant HII region NGC 5471 - linking this outlying starburst with the rest of the galaxy. These FUV-bright features most likely trace hot O & B-type stars along with scattered light from associated nebular dust. Counterparts of the outermost ``crooked arms'' are evident in maps at visible wavelengths and in the 21-cm line of HI. The inner-disk FUV arms are most closely associated with H$\alpha$ knots and the outer (downstream) sides of CO arms. Comparisons of the ``crooked arm'' and ``curly tail'' morphologies with dynamical simulations yield the greatest similitude, when the non- axisymmetric forcing comes from a combination of ``external interactions'' with one or more companion galaxies and ``internal perturbations'' from massive objects orbiting within the disk. We speculate that NGC 5471 represents one of these ``massive disturbers'' within the disk, whose formation followed from a tidal interaction between M101 and a smaller galaxy.
Ultraviolet Signposts of Resonant Dynamics in the Starburst-Ringed Sab Galaxy, M94 (NGC 4736)
William H. Waller,Michael N. Fanelli,William C. Keel,Ralph Bohlin,Nicholas R. Collins,Barry F. Madore,Pamela M. Marcum,Susan G. Neff,Robert W. O'Connell,Joel D. Offenberg,Morton S. Roberts,Andrew M. Smith,Theodore P. Stecher
Physics , 2000, DOI: 10.1086/319384
Abstract: M94 (NGC 4736) is investigated using images from the Ultraviolet Imaging Telescope (FUV-band), Hubble Space Telescope (NUV-band), Kitt Peak 0.9-m telescope (H-alpha, R, and I bands), and Palomar 5-m telescope (B-band), along with spectra from the International Ultraviolet Explorer and Lick 1-m telescopes. The wide-field UIT image shows FUV emission from (a) an elongated nucleus, (b) a diffuse inner disk, where H-alpha is observed in absorption, (c) a bright inner ring of H II regions at the perimeter of the inner disk (R = 48 arcsec. = 1.1 kpc), and (d) two 500-pc size knots of hot stars exterior to the ring on diametrically opposite sides of the nucleus (R= 130 arcsec. = 2.9 kpc). The HST/FOC image resolves the NUV emission from the nuclear region into a bright core and a faint 20 arcsec. long ``mini-bar'' at a position angle of 30 deg. Optical and IUE spectroscopy of the nucleus and diffuse inner disk indicates an approximately 10^7 or 10^8 yr-old stellar population from low-level starbirth activity blended with some LINER activity. Analysis of the H-alpha, FUV, NUV, B, R, and I-band emission along with other observed tracers of stars and gas in M94 indicates that most of the star formation is being orchestrated via ring-bar dynamics involving the nuclear mini-bar, inner ring, oval disk, and outer ring. The inner starburst ring and bi-symmetric knots at intermediate radius, in particular, argue for bar-mediated resonances as the primary drivers of evolution in M94 at the present epoch. Similar processes may be governing the evolution of the ``core-dominated'' galaxies that have been observed at high redshift. The gravitationally-lensed ``Pretzel Galaxy'' (0024+1654) at a redshift of approximately 1.5 provides an important precedent in this regard.
The Ultraviolet Imaging Telescope: Instrument and Data Characteristics
Theodore P. Stecher,Robert H. Cornett,Michael R. Greason,Wayne B. Landsman,Jesse K. Hill,Robert S. Hill,Ralph C. Bohlin,Peter C. Chen,Nicholas R. Collins,Michael N. Fanelli,Joan I. Hollis,Susan G. Neff,Robert W. O'Connell,Joel D. Offenberg,Ronald A. Parise,Joel Wm. Parker,Morton S. Roberts,Andrew M. Smith,William H. Waller
Physics , 1997, DOI: 10.1086/133917
Abstract: The Ultraviolet Imaging Telescope (UIT) was flown as part of the Astro observatory on the Space Shuttle Columbia in December 1990 and again on the Space Shuttle Endeavor in March 1995. Ultraviolet (1200-3300 Angstroms) images of a variety of astronomical objects, with a 40 arcmin field of view and a resolution of about 3 arcsec, were recorded on photographic film. The data recorded during the first flight are available to the astronomical community through the National Space Science Data Center (NSSDC); the data recorded during the second flight will soon be available as well. This paper discusses in detail the design, operation, data reduction, and calibration of UIT, providing the user of the data with information for understanding and using the data. It also provides guidelines for analyzing other astronomical imagery made with image intensifiers and photographic film.
Resonant multi-photon IR dissociation spectroscopy of a trapped and sympathetically cooled biomolecular ion species
Ch. Wellers,A. Borodin,S. Vasilyev,D. Offenberg,S. Schiller
Physics , 2011, DOI: 10.1039/c1cp22428j
Abstract: In this work we demonstrate vibrational spectroscopy of polyatomic ions that are trapped and sympathetically cooled by laser-cooled atomic ions. We use the protonated dipeptide tryptophane-alanine (HTyrAla+) as a model system, cooled by Barium ions to less than 800mK secular temperature. The spectroscopy is performed on the fundamental vibrational transition of a local vibrational mode at 2.74 {\mu}m using a continuous-wave optical parametric oscillator (OPO). Resonant multi-photon IR dissociation spectroscopy (without the use of a UV laser) generates charged molecular fragments, which are sympathetically cooled and trapped, and subsequently released from the trap and counted. We measured the cross section for R-IRMPD under conditions of low intensity, and found it to be approximately two orders smaller than the vibrational excitation cross section. The observed rotational bandwidth of the vibrational transition is larger than the one expected from the combined effects of 300 K black-body temperature, conformer-dependent line shifts, and intermolecular vibrational relaxation broadening (J. Stearns et al., J. Chem. Phys., 127, 154322-7 (2007)). This indicates that as the internal energy of the molecule grows, an increase of the rotational temperature of the molecular ions well above room temperature (up to on the order of 1000K), and/or an appreciable shift of the vibrational transition frequency (approx. 6-8 cm$^{-1}$) occurs.
Translational cooling and storage of protonated proteins in an ion trap at subkelvin temperatures
D. Offenberg,C. B. Zhang,Ch. Wellers,B. Roth,S. Schiller
Physics , 2008, DOI: 10.1103/PhysRevA.78.061401
Abstract: Gas-phase multiply charged proteins have been sympathetically cooled to translational temperatures below 1 K by Coulomb interaction with laser-cooled barium ions in a linear ion trap. In one case, an ensemble of 53 cytochrome c molecules (mass ~ 12390 amu, charge +17 e) was cooled by ~ 160 laser-cooled barium ions to less than 0.75 K. Storage times of more than 20 minutes have been observed and could easily be extended to more than an hour. The technique is applicable to a wide variety of complex molecules.
Measurement of small photodestruction rates of cold, charged biomolecules in an ion trap
D. Offenberg,Ch. Wellers,C. B. Zhang,B. Roth,S. Schiller
Physics , 2008, DOI: 10.1088/0953-4075/42/3/035101
Abstract: In this work, we demonstrate measurements of photodestruction rates of translationally cold, charged biomolecules. The long-term stable storage of the molecular ions in an ion trap at ultra-high vacuum conditions allows measurement of small rates and verification that rates are linear in photodestruction laser intensity. Measurements were performed on singly protonated molecules of the organic compound glycyrrhetinic acid (C30H46O4), dissociated by a continuous-wave UV laser (266 nm) using different intensities. The molecules were sympathetically cooled by simultaneously trapped laser-cooled barium ions to translational temperatures of below 150 mK. Destruction rates of less than 0.05 s^-1 and a cross section of (1.1 +/- 0.1) * 10^-17 cm^2 have been determined. An extension to tunable UV laser sources would permit high-resolution dissociation spectroscopic studies on a wide variety of cold complex molecules.
Assessment of Newly Released and Well-Established Rabbiteye Blueberry ( Vaccinium ashei Reade) Cultivars in North Alabama  [PDF]
Richard Joel Potter, Elina D. Coneva
Agricultural Sciences (AS) , 2018, DOI: 10.4236/as.2018.91007
Abstract: Many cultivars of rabbiteye blueberry (Vaccinium ashei Reade) have been recently developed with diverse vegetative and cropping characteristics, but scientific data on their performance in Alabama is limited. An experiment was established at the North Alabama Horticulture Research Center, Cullman, AL (lat. 34°11'N, long. -86°47'E), USDA Hardiness Zone 7B, to evaluate the performance and horticultural value of the following rabbiteye blueberry cultivars: “Alapaha”, “Baldwin”, “Brightwell”, “Climax”, “Ira”, “Montgomery”, “Onslow”, “Powderblue”, “Premier”, “Tifblue”, and “Yadkin”. Cultivar flowering and ripening season, yield potential, fruit quality characteristics, and vegetative growth were investigated during 2009 and 2010. “Alapaha”, “Climax”, and “Premier” were found to have early ripening in north Alabama. “Alapaha” flowered later than the earliest flowering cultivars, but ripened consistently early, and this later flowering can serve to protect “Alapaha” crop from late freeze damage. Cultivars were not found to differ with respect to their cumulative yield in their fifth and sixth leaf. “Brightwell” and “Climax” had the firmest berries, while “Climax” and “Premier” had the sweetest berries.
A Correlation Between Stellar Activity and the Surface Gravity of Hot Jupiters
Joel D. Hartman
Physics , 2010, DOI: 10.1088/2041-8205/717/2/L138
Abstract: Recently Knutson et al. (2010) have demonstrated a correlation between the presence of temperature inversions in the atmospheres of hot Jupiters, and the chromospheric activity levels of the host stars. Here we show that there is also a correlation, with greater than 99.5% confidence, between the surface gravity of hot Jupiters and the activity levels of the host stars, such that high surface gravity planets tend be found around high activity stars. We also find a less significant positive correlation between planet mass and chromospheric activity, but no significant correlation is seen between planet radius and chromospheric activity. We consider the possibility that this may be due to an observational bias against detecting lower mass planets around higher activity stars, but conclude that this bias is only likely to affect the detection of planets much smaller than those considered here. Finally, we speculate on physical origins for the correlation, including the possibility that the effect of stellar insolation on planetary radii has been significantly underestimated, that strong UV flux evaporates planetary atmospheres, or that high mass hot Jupiters induce activity in their host stars, but do not find any of these hypotheses to be particularly compelling.
STEM and the Humanities  [PDF]
Joel D. Benson
Open Access Library Journal (OALib Journal) , 2017, DOI: 10.4236/oalib.1103476
Abstract:
Students today are told from the time they are in grade school that only by studying STEM subjects can they hope to expect a successful and meaningful career. Many people today question the value of a Liberal Arts education as outdated and elitist, insisting that students who study the Liberal Arts do not develop the skills necessary for the modern work force. To be fair, many faculty members in STEM subjects have acknowledged the importance of a well-rounded education, but we in the Humanities have our own shortcomings in this discussion. Instead of expecting the STEM subjects to recognize the importance of the Liberal Arts, the Humanities needs to reclaim its historical foundation and end this division. STEM subjects are part of the Humanities.
Cosmic Ray Rejection and Image Processing Aboard The Next Generation Space Telescope
H. S. Stockman,D. Fixsen,R. Hanisch,J. C. Mather,M. Nieto-Santisteban,J. D. Offenberg,R. Sengupta,S. Stallcup
Physics , 1998,
Abstract: The NASA Yardstick design for the Integrated Science Instrument Module (ISIM) utilizes 64 1k x 1k InSb imagers. Since multiple readouts per image are required to remove cosmic ray events and to reduce the readout noise, the implied downlink rates can approach 0.7 Tbytes per day. These would exceed the downlink capabilities of RF links from L2 or more distant orbits. Some form of on-board data analysis and compression is mandatory: a factor of 100 compression for an L2 orbit, factors of 1000-10000 for a 1 AU drift-away or 1 x 3 AU elliptical orbit. Supported by funding from JPL to study the uses of low-cost, on- board parallel processors, we are studying algorithms and architectures to perform cosmic-ray rejection and lossless compression of the NIR images, while optimizing the resulting signal- to-noise.
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