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Search Results: 1 - 10 of 593291 matches for " A. L. Hungerford "
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Gamma-Ray Lines from Asymmetric Supernovae
A. L. Hungerford,C. L. Fryer,M. S. Warren
Physics , 2003, DOI: 10.1086/376776
Abstract: We present 3-dimensional SPH simulations of supernova explosions from 100 seconds to 1 year after core-bounce. By extending our modelling efforts to a 3-dimensional hydrodynamics treatment, we are able to investigate the effects of explosion asymmetries on mixing and gamma-ray line emergence in supernovae. A series of initial explosion conditions are implemented, including jet-like and equatorial asymmetries of varying degree. For comparison, symmetric explosion models are also calculated. A series of time slices from the explosion evolution are further analyzed using a 3-dimensional Monte Carlo gamma-ray transport code. The emergent hard X- and gamma-ray spectra are calculated as a function of both viewing angle and time, including trends in the gamma-ray line profiles. We find significant differences in the velocity distribution of radioactive nickel between the symmetric and asymmetric explosion models. The effects of this spatial distribution change are reflected in the overall high energy spectrum, as well as in the individual gamma-ray line profiles.
Choroidal Metastasis from Follicular Cell Thyroid Carcinoma Masquerading as Circumscribed Choroidal Haemangioma
V. P. Papastefanou,A. K. Arora,J. L. Hungerford,V. M. L. Cohen
Case Reports in Oncological Medicine , 2014, DOI: 10.1155/2014/251817
Abstract: Choroidal metastases from follicular thyroid carcinoma are uncommon and usually present as an amelanotic lesion against a background of known systemic disease. We present the case of a 56-year-old woman with a thyroid metastatic focus with unusual clinical presentation, systemic involvement, and early response to systemic treatment. A review of the literature accompanies this case presentation. 1. Case Presentation A 56-year-old lady was referred to the Ocular Oncology Service with a seven-year history of deteriorating visual acuity in the left eye. Patient had a 15-year history of sarcoidosis associated with recurrent uveitis. Best-corrected visual acuity was at 6/36?OS 6/6?OD. At presentation there was no active uveitis. Posterior segment examination revealed an elevated lesion inferotemporally to the macula of the left eye measuring 6.5 × 6.8?mm that was pale orange in colour and difficult to discern clinically from the surrounding retina (Figure 1(a)). A fundus fluorescein angiogram indicated early hyperfluorescence. B-scan ultrasound demonstrated a dome-shaped lesion with high internal reflectivity measuring 2.7?mm in elevation. A Doppler B-scan ultrasound indicated the presence of internal blood flow. Clinical appearance at presentation was typical of a circumscribed choroidal haemangioma although a metastatic deposit remained within the differential diagnosis. No ocular treatment was performed but review was arranged in 3 months pending ongoing investigations for a thyroid gland mass discovered on a routine CT scan of the neck and chest. Figure 1: (a) Pale orange lesion involving the macula and extending inferotemporally before treatment. Clinical appearance is consistent with a circumscribed choroidal haemangioma. (b) After four months a pale, fibrotic scar has developed in the site of the original lesion following treatment. Thyroid gland biopsy proved the mass was a follicular cell carcinoma of the thyroid and systemic staging revealed stage 4 disease due to the presence of bone metastases in the left iliac crest and in the right femur, the latter causing a pathologic fracture. Patient underwent total thyroidectomy. Excision was incomplete and patient received 2 initial sessions of adjuvant treatment of radioactive iodine (131I) therapy (4.9 and 5.8?GBq, resp.). The pathologic fracture was managed with internal fixation and adjuvant external beam radiotherapy (EBRT) with 35?Gy at 15 sessions in the iliac crest and 20?Gy in the femur. Following radioactive treatment of the thyroid gland the visual acuity reduced to counting fingers. Fundus
Trends in Ti44 and Ni56 from Core-Collapse Supernovae
Georgios Magkotsios,Francis X. Timmes,Aimee L. Hungerford,Christopher L. Fryer,Patrick A. Young,Michael Wiescher
Physics , 2010, DOI: 10.1088/0067-0049/191/1/66
Abstract: We compare the yields of Ti44 and Ni56 produced from post-processing the thermodynamic trajectories from three different core-collapse models -- a Cassiopeia A progenitor, a double shock hypernova progenitor, and a rotating 2D explosion -- with the yields from exponential and power-law trajectories. The peak temperatures and densities achieved in these core-collapse models span several of the distinct nucleosynthesis regions we identify, resulting in different trends in the Ti44 and Ni56 yields for different mass elements. The Ti44 and Ni56 mass fraction profiles from the exponential and power-law profiles generally explain the tendencies of the post-processed yields, depending on which regions are traversed by the model. We find integrated yields of Ti44 and Ni56 from the exponential and power-law trajectories are generally within a factor 2 or less of the post-process yields. We also analyze the influence of specific nuclear reactions on the Ti44 and Ni56 abundance evolution. Reactions that affect all yields globally are the 3a, p(e-,nu)n and n(e+,nubar)p. The rest of the reactions are ranked according to their degree of impact on the synthesis of Ti44. The primary ones include Ti44(a,p)V47, Ca40(a,g)Ti44, V45(p,g)Cr46, Ca40(a,p)Sc43, F17(a,p)Ne20, Na21(a,p)Mg24, Sc41(p,g)Ti42, Sc43(p,g)Ti44, Ti44(p,g)V45, and Ni57(p,g)Cu58, along with numerous weak reactions. Our analysis suggests that not all Ti44 need be produced in an a-rich freeze-out in core-collapse events, and that reaction rate equilibria in combination with timescale effects for the expansion profile may account for the paucity of Ti44 observed in supernovae remnants.
Spectra and Light Curves of Failed Supernovae
Chris L. Fryer,Peter J. Brown,Filomena Bufano,Jon A. Dahl,Christopher J. Fontes,Lucille H. Frey,Stephen T. Holland,Aimee L. Hungerford,Stefan Immler,Paolo Mazzali,Peter A. Milne,Evan Scannapieco,Nevin Weinberg,Patrick A. Young
Physics , 2009, DOI: 10.1088/0004-637X/707/1/193
Abstract: Astronomers have proposed a number of mechanisms to produce supernova explosions. Although many of these mechanisms are now not considered primary engines behind supernovae, they do produce transients that will be observed by upcoming ground-based surveys and NASA satellites. Here we present the first radiation-hydrodynamics calculations of the spectra and light curves from three of these "failed" supernovae: supernovae with considerable fallback, accretion induced collapse of white dwarfs, and energetic helium flashes (also known as type .Ia supernovae).
Genetically distant American Canine distemper virus lineages have recently caused epizootics with somewhat different characteristics in raccoons living around a large suburban zoo in the USA
John A Lednicky, Jean Dubach, Michael J Kinsel, Thomas P Meehan, Maurizio Bocchetta, Laura L Hungerford, Nicolene A Sarich, Kelley E Witecki, Michael D Braid, Casandra Pedrak, Christiane M Houde
Virology Journal , 2004, DOI: 10.1186/1743-422x-1-2
Abstract: Phylogenetic analyses of subgenomic CDV fusion (F) -, phosphoprotein (P) -, and complete hemagglutinin (H) – gene sequences indicated that distinct American CDV lineages caused the distemper epizootics. The 1998 outbreak was caused by viruses that are likely from an old CDV lineage that includes CDV Snyder Hill and Lederle, which are CDV strains from the early 1950's. The 2000 and 2001 viruses appear to stem from the lineage of CDV A75/17, which was isolated in the mid 1970's. Only the 2001 viruses formed large syncytia in brain and/or lung tissue, and during primary isolation in-vitro in Vero cells, demonstrating at least one phenotypic property by which they differed from the other viruses.Two different American CDV lineages caused the raccoon distemper outbreaks. The 1998 viruses are genetically distant to the 2000/2001 viruses. Since CDV does not cause persistent infections, the cycling of different CDV lineages within the same locale suggests multiple reintroductions of the virus to area raccoons. Our findings establish a precedent for determining whether the perceived differences in mortality rates are actual and attributable in part to inherent differences between CDV strains arising from different CDV lineages.Canine distemper virus (CDV) (family Paramyxoviridae, genus Morbillivirus) is a single-stranded (negative-sense) enveloped RNA virus that is highly contagious and transmitted predominantly by aerosols [1]. Long known to cause potentially lethal disease among members of the Canidae, Mustelidae, and Procyonidae, CDV has recently been detected as a cause of morbidity and mortality in large felids [2], fresh-water seals (Phoca sibirica) [3], and various other animals. CDV killed more than 10,000 Caspian seals (Phoca caspica) in year 2000 [4], and decimated an African wild dog (an endangered species) breeding pack [5], demonstrating that CDV epidemics can be catastrophic. It also killed 1/3 of the Serengeti lions (Panthera leo) in 1994, whereas mortality du
Solar neutrino detection in a large volume double-phase liquid argon experiment
D. Franco,C. Giganti,P. Agnes,L. Agostino,B. Bottino,S. Davini,S. De Cecco,A. Fan,G. Fiorillo,C. Galbiati,A. M. Goretti,E. V. Hungerford,Al. Ianni,An. Ianni,C. Jollet,L. Marini,C. J. Martoff,A. Meregaglia,L. Pagani,M. Pallavicini,E. Pantic,A. Pocar,A. L. Renshaw,B. Rossi,N. Rossi,Y. Suvorov,G. Testera,A. Tonazzo,H. Wang,S. Zavatarelli
Physics , 2015,
Abstract: The direct search for dark matter WIMP particles through their interaction with nuclei at the "neutrino floor" sensitivity, where neutrino-induced coherent scattering on nuclei starts contributing to the background, requires detectors capable of collecting exposures of the order of 1~ktonne yr free of background resulting from beta and gamma decays and cosmogenic and radiogenic neutrons. The same constraints are required for precision measurements of solar neutrinos elastically scattering on electrons. Two-phase liquid argon time projection chambers (LAr TPCs) are prime candidates for the ambitious program to explore the nature of dark matter. The large target, high scintillation light yield and good spatial resolution in all three cartesian directions concurrently allows a high precision measurement of solar neutrino fluxes. We studied the cosmogenic and radiogenic backgrounds affecting solar neutrino detection in a 300 tonne (100 tonne fiducial) LAr TPC operating at LNGS depth (3,800 meters of water equivalent). Such a detector could measure the CNO neutrino rate with 5 sigma sensitivity, and significantly improve the precision of the 7Be and pep neutrino rates compared to the currently available results from the Borexino organic liquid scintillator detector. Measurements with ~2%, ~10% and ~15% precision for 7Be, pep, and CNO neutrinos, respectively, are possible.
A. Fluka Study of Underground Cosmogenic Neutron Production
A Empl,E. V. Hungerford,R. Jasim,P. Mosteiro
Physics , 2014, DOI: 10.1088/1475-7516/2014/08/064
Abstract: Neutrons produced by cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically such neutrons can dominate the background, as they are particularly difficult to shield and detect. Since actual data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. Thus validation of any simulation code is necessary to assure reliable results. This work compares in detail the predictions of the FLUKA simulation code to existing data, and uses this code to report a simulation of cosmogenic backgrounds for typical detectors embedded in a water tank with liquid scintillator shielding.
Study of Cosmogenic Neutron Backgrounds at LNGS
A. Empl,R. Jasim,E. Hungerford,P. Mosteiro
Physics , 2012,
Abstract: Cosmic muon interactions are important contributors to backgrounds in underground detectors when searching for rare events. Typically neutrons dominate this background as they are particularly difficult to shield and detect in a veto system. Since actual background data is sparse and not well documented, simulation studies must be used to design shields and predict background rates. This means that validation of any simulation code is necessary to assure reliable results. This work studies the validation of the FLUKA simulation code, and reports the results of a simulation of cosmogenic background for a liquid argon two-phase detector embedded within a water tank and liquid scintillator shielding.
A New Method for Measuring Coherent Elastic Neutrino Nucleus Scattering at an Off-Axis High-Energy Neutrino Beam Target
S. J. Brice,R. L. Cooper,F. DeJongh,A. Empl,L. M. Garrison,A. Hime,E. Hungerford,T. Kobilarcik,B. Loer,C. Mariani,M. Mocko,G. Muhrer,R. Pattie,Z. Pavlovic,E. Ramberg,K. Scholberg,R. Tayloe,R. T. Thornton,J. Yoo,A. Young
Physics , 2013, DOI: 10.1103/PhysRevD.89.072004
Abstract: We present a new experimental method for measuring the process of Coherent Elastic Neutrino Nucleus Scattering (CENNS). This method uses a detector situated transverse to a high energy neutrino beam production target. This detector would be sensitive to the low energy neutrinos arising from pion decays-at-rest in the target. We discuss the physics motivation for making this measurement and outline the predicted backgrounds and sensitivities using this approach. We report a measurement of neutron backgrounds as found in an off-axis surface location of the Fermilab Booster Neutrino Beam (BNB) target. The results indicate that the Fermilab BNB target is a favorable location for a CENNS experiment.
Spectra of Type Ia Supernovae from Double Degenerate Mergers
Chris L. Fryer,Ashley J. Ruiter,Krzysztof Belczynski,Peter J. Brown,Filomena Bufano,Steven Diehl,Christopher J. Fontes,Lucille H. Frey,Stephen T. Holland,Aimee L. Hungerford,Stefan Immler,Paolo Mazzali,Casey Meakin,Peter A. Milne,Cody Raskin,Francis X. Timmes
Physics , 2010, DOI: 10.1088/0004-637X/725/1/296
Abstract: The merger of two white dwarfs (a.k.a. double degenerate merger) has often been cited as a potential progenitor of type Ia supernovae. Here we combine population synthesis, merger and explosion models with radiation-hydrodynamics light-curve models to study the implications of such a progenitor scenario on the observed type Ia supernova population. Our standard model, assuming double degenerate mergers do produce thermonuclear explosions, produces supernova light-curves that are broader than the observed type Ia sample. In addition, we discuss how the shock breakout and spectral features of these double degenerate progenitors will differ from the canonical bare Chandrasekhar-massed explosion models. We conclude with a discussion of how one might reconcile these differences with current observations.
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