1,541 research outputs found

    Improving the Acquisition and Management of Sample Curation Data

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    This paper discusses the current sample documentation processes used during and after a mission, examines the challenges and special considerations needed for designing effective sample curation data systems, and looks at the results of a simulated sample result mission and the lessons learned from this simulation. In addition, it introduces a new data architecture for an integrated sample Curation data system being implemented at the NASA Astromaterials Acquisition and Curation department and discusses how it improves on existing data management systems

    Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

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    We present initial results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra's superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the `ionization cone' in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the spatially resolved spectra as a function of distance from the nucleus.Comment: 5 pages, 2 figures, 1 video. To appear in refereed Proceedings of "X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September 7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin

    Electrostatic Interactions of Asymmetrically Charged Membranes

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    We predict the nature (attractive or repulsive) and range (exponentially screened or long-range power law) of the electrostatic interactions of oppositely charged and planar plates as a function of the salt concentration and surface charge densities (whose absolute magnitudes are not necessarily equal). An analytical expression for the crossover between attractive and repulsive pressure is obtained as a function of the salt concentration. This condition reduces to the high-salt limit of Parsegian and Gingell where the interaction is exponentially screened and to the zero salt limit of Lau and Pincus in which the important length scales are the inter-plate separation and the Gouy-Chapman length. In the regime of low salt and high surface charges we predict - for any ratio of the charges on the surfaces - that the attractive pressure is long-ranged as a function of the spacing. The attractive pressure is related to the decrease in counter-ion concentration as the inter-plate distance is decreased. Our theory predicts several scaling regimes with different scaling expressions for the pressure as function of salinity and surface charge densities. The pressure predictions can be related to surface force experiments of oppositely charged surfaces that are prepared by coating one of the mica surfaces with an oppositely charged polyelectrolyte

    NEW ENVIRONMENTALLY BENIGN LEATHER TECHNOLOGY: COMBINATION TANNING USING VEGETABLE TANNIN, NAPHTHOL AND OXAZOLIDINE

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    ABSTRACTLeather tanning is a process of converting of skin or hide protein into leather with adequate strength properties, resistance to various biological and physical agents, and capable of being used for a wide range of purposes.  Leather tanning reactions between collagen-vegetable tannin-oxazolidine and collagen-dihydroxynaphthalenes (DHNs)-oxazolidine have been investigated using hide powder and sheepskin pickled pelt. This investigation showed that some DHNs have a tanning effect on collagen.  The measurement of combined and cross-linked vegetable tannin and DHNs on collagen showed that 20-50% vegetable tannin, 1,6- and 2,6-DHNs were fixed through covalent bonding.  Shrinkage temperature of the leather changed little after the non combined vegetable tannin and DHNs had been removed from the leather, indicating that the high stability of the combination tanned leather comes from the covalent bonding formed between vegetable tannage or DHNs and collagen through oxazolidine. Covalently bound tannin on collagen was more stable and could not be extracted by lyotropic agents. Keywords: tanning, leather, hydrothermal stability, vegetable tannage, dihydroxynaphthalenes, oxazolidine

    NEW ENVIRONMENTALLY BENIGN LEATHER TECHNOLOGY: COMBINATION TANNING USING VEGETABLE TANNIN, NAPHTHOL AND OXAZOLIDINE

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    ABSTRACTLeather tanning is a process of converting of skin or hide protein into leather with adequate strength properties, resistance to various biological and physical agents, and capable of being used for a wide range of purposes.  Leather tanning reactions between collagen-vegetable tannin-oxazolidine and collagen-dihydroxynaphthalenes (DHNs)-oxazolidine have been investigated using hide powder and sheepskin pickled pelt. This investigation showed that some DHNs have a tanning effect on collagen.  The measurement of combined and cross-linked vegetable tannin and DHNs on collagen showed that 20-50% vegetable tannin, 1,6- and 2,6-DHNs were fixed through covalent bonding.  Shrinkage temperature of the leather changed little after the non combined vegetable tannin and DHNs had been removed from the leather, indicating that the high stability of the combination tanned leather comes from the covalent bonding formed between vegetable tannage or DHNs and collagen through oxazolidine. Covalently bound tannin on collagen was more stable and could not be extracted by lyotropic agents. Keywords: tanning, leather, hydrothermal stability, vegetable tannage, dihydroxynaphthalenes, oxazolidine

    Salvage Fractionated Stereotactic Re-irradiation (FSRT) for Patients with Recurrent High Grade Gliomas Progressed after Bevacizumab Treatment

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    Purpose/Objectives: Bevacizumab failure is a major clinical problem in the manage- ment of high grade gliomas (HGG), with a median overall survival of less than 4 months (m). This study evaluated the efficacy of fractionated stereotactic re-irradiation (FSRT) for patients with HGG after progression on Bevacizumab. Materials/Methods: Retrospective review was conducted of patients treated with FSRT after progression on bevacizumab. A total of 36 patients were identified. FSRT was most commonly delivered in 3.5 Gy fractions to a total dose of 35 Gy. Survival from initial diagnosis, as well as from recurrence and re-irradiation, were utilized as study endpoints. Univariate and multivariate analysis was performed. Results: Among the 36 patients, 31 patients had recurrent glioblastoma, and 5 patients had recurrent anaplastic astrocytoma. The median time from initial bevacizumab treatment to FSRT was 8.5 m (range 2.3 – 32.0 m). The median plan target volume for FSRT was 27.5 cc (range 1.95 – 165 cc). With a median follow up of 20.4 m, the overall survival of the patients since initial diagnosis was also 24.9 m. The median overall survival after initiation of bevacizumab was 13.4 months. The median overall survival from FSRT was 4.8 m. FSRT treatment was well tolerated with no Grade \u3e3 toxicity. Conclusions: Favorable outcomes were observed in patients with recurrent HGG who received salvage FSRT after bevacizumab failure. The treatment was well tolerated. Prospective study is warranted to further evaluate the efficacy of salvage FSRT for selected patients with recurrent HGG amenable to FSRT, who had failed bevacizumab treatment

    Possible Evidence for MeV Dark Matter In Dwarf Spheroidals

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    It has been recently proposed that the observed 511 keV emission from the Galactic bulge could be the product of very light (1-100 MeV) annihilating dark matter particles. Other possible explanations for this signal are associated with stellar objects, such as hypernovae. In order to distinguish between annihilating light dark matter scenario and more conventional astrophysical sources for the bulge emission, we here propose the study of dwarf spheroidals such as Sagittarius. These galaxies have typical luminosities of 105L⊙10^5 L_\odot but mass-to-light ratios of ∼100\sim 100. As there are comparatively few stars, the prospects for 511 keV emission from standard astrophysical scenarios are minimal. The dwarf spheroidals do, however, contain copious amounts of dark matter. INTEGRAL/SPI has observed the Sagittarius region. Analysis of this data for 511 keV emission will provide a test of MeV dark matter which can distinguish between annihilating dark matter and more standard astrophysics. The observation of such a signal from Sagittarius should be a ``smoking gun'' for MeV dark matter.Comment: 4 pages, no figures. Version accepted by Physical Review Letter

    Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

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    We present initial results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra's superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the `ionization cone' in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the spatially resolved spectra as a function of distance from the nucleus

    Time-resolved Neutron-gamma-ray Data Acquisition for in Situ Subsurface Planetary Geochemistry

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    The current gamma-ray/neutron instrumentation development effort at NASA Goddard Space Flight Center aims to extend the use of active pulsed neutron interrogation techniques to probe the subsurface elemental composition of planetary bodies in situ. Previous NASA planetary science missions, that used neutron and/or gamma-ray spectroscopy instruments, have relied on neutrons produced from galactic cosmic rays. One of the distinguishing features of this effort is the inclusion of a high intensity 14.1 MeV pulsed neutron generator synchronized with a custom data acquisition system to time each event relative to the pulse. With usually only one opportunity to collect data, it is difficult to set a priori time-gating windows to obtain the best possible results. Acquiring time-tagged, event-by-event data from nuclear induced reactions provides raw data sets containing channel/energy, and event time for each gamma ray or neutron detected. The resulting data set can be plotted as a function of time or energy using optimized analysis windows after the data are acquired. Time windows can now be chosen to produce energy spectra that yield the most statistically significant and accurate elemental composition results that can be derived from the complete data set. The advantages of post-processing gamma-ray time-tagged event-by-event data in experimental tests using our prototype instrument will be demonstrated

    Searching for AGN Outflows: Spatially Resolved Chandra HETG Spectroscopy of the NLR Ionization Cone in NGC 1068

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    We present initial results from a new 440-ks Chandra HETG GTO observation of the canonical Seyfert 2 galaxy NGC 1068. The proximity of NGC 1068, together with Chandra’s superb spatial and spectral resolution, allow an unprecedented view of its nucleus and circumnuclear NLR. We perform the first spatially resolved high-resolution X-ray spectroscopy of the ‘ionization cone’ in any AGN, and use the sensitive line diagnostics offered by the HETG to measure the ionization state, density, and temperature at discrete points along the ionized NLR. We argue that the NLR takes the form of outflowing photoionized gas, rather than gas that has been collisionally ionized by the small-scale radio jet in NGC 1068. We investigate evidence for any velocity gradients in the outflow, and describe our next steps in modeling the spatially resolved spectra as a function of distance from the nucleus
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