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  • 1
    Electronic Resource
    Electronic Resource
    Conformation of C-1-Substituted Pyranos-1-yl and Pyranosan-5-yl Radicals Evidence for a Quasi-Homo-Anomeric Stabilization Effect (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1155-1160 
    Details
    ISSN: 0009-2940
    Keywords: Carbohydrate radicals ; Conformational analysis ; ESR spectroscopy ; Anomeric effect ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetylated 1-cyano- and 1-chloro-pyranos-1-yl radicals and 5-acetoxycarbonyl-, 5-methoxycarbonyl-, and 5-unsubstituted pyranosan-5-yl radicals were generated from the corresponding bromides by bromine abstraction with trimethyltin radicals. The conformation of these radicals, as deduced from the ESR hyperfine splittings, is explained by the combined action of a quasi-anomeric and a homo-anomeric stabilization effect. A captodative substitution pattern of the radical center does not influence the conformations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230532
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Rearrangements of Free Radicals, XIII[1]. Thermal and Photochemical Rearrangements of Cyclic C8H9 Radicals in Adamantane Matrix (1993)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 126 (1993), S. 1917-1927 
    Details
    ISSN: 0009-2940
    Keywords: Free radicals ; Rearrangement ; ESR spectroscopy ; Adamantane matrix ; Molecular orbital calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ESR spectra observed after X-irradiation of bicyclo-[5.1.0]octa-2,5-diene (homotropylidene) (12) in a [D16]adamantane matrix at 210 K have been identified to be mainly due to the cyclooctatrienyl radical (8), formed by thermal ring opening of the initial bicyclo[5.1.0]octa-2,5-diene-4-yl (homotropylidenyl) radical (7). The same spectrum has also been observed in X-irradiation of bromocyclooctatriene and a mixture of bromocyclooctatriene and 7-bromobicyclo[4.2.0]cycloocta-2,4-diene in a [D16]adamantane matrix. In all cases, UV irradiation of the matrix caused an irreversible transformation of radical 8 (and probably 7) into the bicyclo[3.3.0]octa-2,6-diene-4-yl radical (17). Tricyclo[3.3.0.02,4]oct-6-en-7-yl radical (19), generated by X-irradiation of tricyclo[3.3.0.02,4]oct-2-ene (20) in adamantane, is thermally stable up to 370 K, but also undergoes a facile rearrangement to the radical 17 on UV irradiation. This process is reasonably explained to occur stepwise via radicals 7 and 8. The postulated reaction paths and the spectral assignments are supported by semiempirical (AM1, PM3), abinitio (UHF/3-21G*), and molecular mechanics (MM2ERW) calculations, which are in accord with the finding that 8 is energetically more stable than 7. The quantum mechanical calculations predict that a degenerate sigmatropic circumambulation of the cyclopropane ring in radical 7 should favorably compete with its ring opening.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19931260824
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational effects in 2-deoxyglucopyranos-1-yl radicals (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1891-1898 
    Details
    ISSN: 0009-2940
    Keywords: ESR spectroscopy ; Conformational analysis ; Carbohydrate radicals ; Anomeric effect ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2-Unsubstituted and 2-substituted (fluoro, tosylamino, n-propyl) 3,4,6-tri-O-acetyl-2-deoxypyranosyl radicals are obtained by reaction of the corresponding pyranosyl bromides or phenylselenides with photolytically generated trimethyltin radicals in benzene solution. Analysis of the ESR hyperfine splittings reveals that the 2-deoxy-2-fluoroglucopyranosyl radical exists in a boat-like conformation at room temperature, whereas the others retain the 4C1 chair conformation of the starting material. The observed conformational effects are explained by a “quasi-homo-anomeric” frontier orbital interaction of the nx lone pair of the ring oxygen atom with the σ* MO of the β-C-O bond, in which the singly occupied p orbital at C-1 acts as a mediator for this 1,3-anomeric interaction.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19901230922
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  • 4
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    First All-Sky Search for Continuous Gravitational Waves from Unknown Sources in Binary Systems (2014)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to 2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from 0.6 10(exp 3) ls to 6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3 10(exp 24) at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN22620 , Physical Review D (ISSN 0031-899X) (e-ISSN 1536-6065); 90; 6; 062010
    Format: text
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  • 5
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    Parameter Estimation for Compact Binary Coalescence Signals with the First Generation Gravitational-Wave Detector Network (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Compact binary systems with neutron stars or black holes are one of the most promising sources for ground-based gravitational-wave detectors. Gravitational radiation encodes rich information about source physics; thus parameter estimation and model selection are crucial analysis steps for any detection candidate events. Detailed models of the anticipated waveforms enable inference on several parameters, such as component masses, spins, sky location and distance, that are essential for new astrophysical studies of these sources. However, accurate measurements of these parameters and discrimination of models describing the underlying physics are complicated by artifacts in the data, uncertainties in the waveform models and in the calibration of the detectors. Here we report such measurements on a selection of simulated signals added either in hardware or software to the data collected by the two LIGO instruments and the Virgo detector during their most recent joint science run, including a blind injection where the signal was not initially revealed to the collaboration. We exemplify the ability to extract information about the source physics on signals that cover the neutron-star and black-hole binary parameter space over the component mass range 1M25M and the full range of spin parameters. The cases reported in this study provide a snapshot of the status of parameter estimation in preparation for the operation of advanced detectors.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN12729 , Physical Review D (ISSN 2470-0010) (e-ISSN 2470-0029); 88; 062001
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  • 6
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    Remote and In Situ Observations of an Unusual Earth-Directed Coronal Mass Ejection from Multiple Viewpoints (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: During June 16-21, 2010, an Earth-directed Coronal Mass Ejection (CME) event was observed by instruments onboard STEREO, SOHO, MESSENGER and Wind. This event was the first direct detection of a rotating CME in the middle and outer corona. Here, we carry out a comprehensive analysis of the evolution of the CME in the interplanetary medium comparing in-situ and remote observations, with analytical models and three-dimensional reconstructions. In particular, we investigate the parallel and perpendicular cross section expansion of the CME from the corona through the heliosphere up to 1 AU. We use height-time measurements and the Gradual Cylindrical Shell (GCS) technique to model the imaging observations, remove the projection effects, and derive the 3-dimensional extent of the event. Then, we compare the results with in-situ analytical Magnetic Cloud (MC) models, and with geometrical predictions from past works. We nd that the parallel (along the propagation plane) cross section expansion agrees well with the in-situ model and with the Bothmer & Schwenn [1998] empirical relationship based on in-situ observations between 0.3 and 1 AU. Our results effectively extend this empirical relationship to about 5 solar radii. The expansion of the perpendicular diameter agrees very well with the in-situ results at MESSENGER ( 0:5 AU) but not at 1 AU. We also find a slightly different, from Bothmer & Schwenn [1998], empirical relationship for the perpendicular expansion. More importantly, we find no evidence that the CME undergoes a significant latitudinal over-expansion as it is commonly assumed
    Keywords: Astrophysics
    Type: GSFC.JA.00285.2012
    Format: application/pdf
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  • 7
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    Supplement: The Rate of Binary Black Hole Mergers Inferred from Advanced LIGO Observations Surrounding GW150914 (2016)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This article provides supplemental information for a Letter reporting the rate of (BBH) coalescences inferred from 16 days of coincident Advanced LIGO observations surrounding the transient (GW) signal GW150914. In that work wereported various rate estimates whose 90% confidence intervals fell in the range 2600 Gpc(exp -3) yr(exp -1). Here we givedetails on our method and computations, including information about our search pipelines, a derivation of ourlikelihood function for the analysis, a description of the astrophysical search trigger distribution expected frommerging BBHs, details on our computational methods, a description of the effects and our model for calibrationuncertainty, and an analytic method for estimating our detector sensitivity, which is calibrated to our measurements.
    Keywords: Astrophysics
    Type: GSFC-E-DAA-TN44086 , The Astrophysical Journal: Supplement Series (ISSN 0067-0049) (e-ISSN 1538-4365); 227; 2; 14
    Format: text
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