Science.gov

Sample records for exocyclic rings part

  1. Tetra-2,3-pyrazinoporphyrazines with externally appended pyridine rings. 15. Effects of the pyridyl substituents and fused exocyclic rings on the UV-visible spectroscopic properties of Mg(II)-porphyrazines: a combined experimental and DFT/TDDFT study.

    PubMed

    Donzello, Maria Pia; De Mori, Giorgia; Viola, Elisa; Ercolani, Claudio; Ricciardi, Giampaolo; Rosa, Angela

    2014-08-04

    Two new Mg(II) porphyrazine macrocycles, the octakis(2-pyridyl)porphyrazinato-magnesium(II), [Py8PzMg(H2O)], and the tetrakis-[6,7-di(2-pyridyl)quinoxalino]porphyrazinato-magnesium(II), [Py8QxPzMg(H2O)], were prepared by Mg-template macrocyclization processes, and their general physicochemical properties were examined. The previously reported porphyrazine analog, the tetrakis-2,3-[5,6-di(2-pyridyl)-pyrazino]porphyrazinato-magnesium(II), [Py8PyzPzMg(H2O)], has been also considered in the present work. The UV-visible solution spectra in nonaqueous solvents of this triad of externally octapyridinated Mg(II) complexes exhibit the usual profile observed for phthalocyanine and porphyrazine macrocycles, with intense absorptions in the Soret (300-450 nm) and Q band (600-800 nm) regions. It is observed that the Q band maximum sensibly shifts toward the red with peak values at 635 → 658 → 759 nm along the series [Py8PzMg(H2O)], [Py8PyzPzMg(H2O)], and [Py8QxPzMg(H2O)], as the extension of the macrocycle π-system increases. TDDFT calculations of the electronic absorption spectra were performed for the related water-free model compounds [Py8PzMg], [Py8PyzPzMg], and [Py8QxPzMg] to provide an interpretation of the UV-visible spectral changes occurring upon introduction of the pyrazine and quinoxaline rings at the periphery of the Pz macrocycle. To discriminate the electronic effects of the fused exocyclic rings from those of the appended 2-pyridyl rings, the UV-visible spectra of [PzMg] and [PyzPzMg] were also theoretically investigated. The theoretical results prove to agree very well with the experimental data, providing an accurate description of the UV-visible spectra. The observed spectral changes are interpreted on the basis of the electronic structure changes occurring along the series.

  2. Exocyclic push-pull conjugated compounds. Part 3. An experimental NMR and theoretical MO ab initio study of the structure, the electronic properties and barriers to rotation about the exocyclic partial double bond in 2- exo-methylene- and 2-cyanoimino-quinazolines and -benzodiazepines

    NASA Astrophysics Data System (ADS)

    Benassi, R.; Bertarini, C.; Hilfert, L.; Kempter, G.; Kleinpeter, E.; Spindler, J.; Taddei, F.; Thomas, S.

    2000-03-01

    The structure of a number of 2- exo-methylene substituted quinazolines and benzodiazepines, respectively, 1, 3a, b, 4( X=-CN, -COOEt ) and their 2-cyanoimino substituted analogues 2, 3c, d( X=-CN, -SO 2C 6H 4-Me (p) was completely assigned by the whole arsenal of 1D and 2D NMR spectroscopic methods. The E/ Z isomerism at the exo-cyclic double bond was determined by both NMR spectroscopy and confirmed by ab initio quantum chemical calculations; the Z isomer is the preferred one, its amount proved dependent on steric hindrance. Due to the push-pull effect in this part of the molecules the restricted rotation about the partial C 2,C 11 and C 2,N 11 double bonds, could also be studied and the barrier to rotation measured by dynamic NMR spectroscopy. The free energies of activation of this dynamic process proved very similar along the compounds studied but being dependent on the polarity of the solvent. Quantum chemical calculations at the ab initio level were employed to prove the stereochemistry at the exo-cyclic partial double bonds of 1- 4, to calculate the barriers to rotation but also to discuss in detail both the ground and the transition state of the latter dynamic process in order to better understand electronic, inter- and intramolecular effects on the barrier to rotation which could be determined experimentally. In the cyanoimino substituted compounds 2, 3c, d, the MO ab initio calculations evidence the isomer interconversion to be better described by the internal rotation process than by the lateral shift mechanism.

  3. Structural features of an exocyclic adduct positioned opposite an abasic site in a DNA duplex

    SciTech Connect

    Kouchakdjian, M.; Patel, D.J. ); Eisenberg, M.; Johnson, F.; Grollman, A.P. )

    1991-04-02

    Structural studies have been extended to dual lesions where an exocyclic adduct is positioned opposite an abasic site in the center of a DNA oligomer duplex. NMR and energy minimization studies were performed on the 1,N{sup 2}-propanodeoxyguanosine exocyclic adduct (X) positioned opposite a tetrahydrofuran abasic site (F) with the dual lesions located in the center of the (C1-A2-T3-G4-X5-G6-T7-A8-C9){center dot}(G10-T11-A12-C13-F14-C15-A16-T17-G18) X{center dot}F 9-mer duplex. Two-dimensional NMR experiments establish that the X{center dot}F 9-mer helix is right-handed with Watson-Crick A{center dot}T and G{center dot}C base pairing on either side of the lesion site. NOEs are detected from the methylene protons of the exocyclic ring of X5 to the imino protons of G4{center dot}C15 and G6{center dot}C13 which flank the lesion site, as well as to the H1{prime} and H1{double prime} protons of the cross strand F14 tetrahydrofuran moiety. These NMR results establish that the exocyclic adduct X5 is positioned between flanking G4{center dot}C15 and G6{center dot}C13 base pairs and directed toward the abasic lesion F14 on the partner strand. These studies establish that the exocyclic ring of the 1,N{sup 2}-propanodeoxyguanosine adduct fits into the cavity generated by the abasic site.

  4. Nuclear magnetic resonance and molecular modeling study of exocyclic carbon-carbon double bond polarization in benzylidene barbiturates

    NASA Astrophysics Data System (ADS)

    Figueroa-Villar, J. Daniel; Vieira, Andreia A.

    2013-02-01

    Benzylidene barbiturates are important materials for the synthesis of heterocyclic compounds with potential for the development of new drugs. The reactivity of benzylidene barbiturates is mainly controlled by their exocyclic carbon-carbon double bond. In this work, the exocyclic double bond polarization was estimated experimentally by NMR and correlated with the Hammett σ values of the aromatic ring substituents and the molecular modeling calculated atomic charge difference. It is demonstrated that carbon chemical shift differences and NBO charge differences can be used to predict their reactivity.

  5. Vibration of Thin Circular Rings. Part II. Modal Functions and Eigenvalues of Constrained Semicircular Rings

    NASA Technical Reports Server (NTRS)

    Lang, T. E.

    1963-01-01

    The equations of motion of thin circular rings are derived and solved for in-plane in-extensional deformation. Modal characteristics are tabulated for the five lowest flexural modes of vibration of semicircular ring segments for the possible combinations of homogeneous boundary conditions that can occur.

  6. Structure sensitivity of hydrogenolytic cleavage of endocyclic and exocyclic C-C bonds in methylcyclohexane over supported iridium particles

    SciTech Connect

    Shi, Hui; Gutierrez, Oliver Y.; Haller, Gary L.; Mei, Donghai; Rousseau, Roger J.; Lercher, Johannes A.

    2013-01-02

    Structure sensitivities, H2 pressure effects and temperature dependencies for rates and selectivities of endo- and exocyclic C–C bond cleavage in methylcyclohexane were studied over supported Ir catalysts. The rate of endocyclic C–C bond cleavage first decreased and then increased with declining Ir dispersion from 0.65 to 0.035. The ring opening (RO) product distribution remained unchanged with varying H2 pressure on small Ir particles, while further shifting to methylhexanes with increasing H2 pressure on large particles. In contrast, the rate and selectivity of exocyclic C–C bond cleavage decreased monotonically with increasing H2 pressure and decreasing Ir particle size. The distinct dependencies of endocyclic and exocyclic C–C bond cleavage pathways on Ir dispersion and H2 pressure suggest that they are mediated by surface species with different ensemble size requirements. DFT calculations were performed on an Ir50 cluster and an Ir(111) surface, with or without pre-adsorbed hydrogen atoms, to provide insight into the observed effects of particle size and H2 pressure on RO pathways. On small Ir particles, the calculated dehydrogenation enthalpies for all endocyclic bonds were similar and affected to similar extents by H2 pressure; on large particles, the selectivity to n-heptane (via substituted C-C bond cleavage) was even lower than on small particles as a result of the least favorable adsorption and dehydrogenation energetics for hindered bonds. This work was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences under Contract DE-AC05-76RL01830. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. The computing time is provided by the user project from EMSL, a national scientific user facility sponsored by the US Department of Energy's Office of Biological and Environmental Research and located at Pacific

  7. A study of exocyclic radical reductions of polysubstituted tetrahydropyrans.

    PubMed

    Godin, François; Prévost, Michel; Viens, Frédérick; Mochirian, Philippe; Brazeau, Jean-François; Gorelsky, Serge I; Guindon, Yvan

    2013-06-21

    Exocyclic radical reductions were thoroughly investigated in the context of the synthesis of polysubstituted tetrahydropyrans, which are found in numerous macrolides. The radical precursors studied herein were generated by tandem cycloetherification and iodoetherification reactions or, alternatively, by semicyclic acetals substitutions. DFT calculations (BHandHLYP/TZVP) performed at the transition-state level for the hydrogen radical delivery are in good accordance with the experimental data and enabled the identification of important conformational factors that govern the selectivities obtained. This study demonstrates that both the preferred reactive conformation of the radical and steric interactions with the incoming hydride have to be considered in order to fully rationalize the levels of diastereoselection generated in acyclic free-radical processes.

  8. Collision of a vortex ring on granular material. Part II. Erosion of the granular layer

    NASA Astrophysics Data System (ADS)

    Yoshida, Junya; Masuda, Naoya; Ito, Boku; Furuya, Takayoshi; Sano, Osamu

    2012-02-01

    In our previous paper (part I), an experimental result was presented on the normal impact of a vortex ring on the granular layer (glass beads of diameter 0.10 mm), which was placed at a specified distance from the outlet of the vortex ring generator. The Reynolds number of the vortex ring ranged from 1000 to 6000, whereas the traveling distance ranged from 2 to 13 times of the diameter of the vortex ring generator nozzle. In part I, the deformation of the vortex ring impacting on the granular layer and the development of the secondary vortex ring were focused. In this paper (part II), the erosion of the granular surface by the vortex ring is described. Various patterns were found depending on the Reynolds number of the vortex ring and the traveling distance. Two patterns, one (grooves) which has radial striations from the central depressed region to the outer edge of the rim and the other (dimples) which is characterized by isolated small depressions around the outer edge of the rim, are examined in detail. The formation processes of these patterns are elucidated in terms of the deformation of the vortex ring.

  9. A simple method for N-15 labelling of exocyclic amino groups in synthetic oligodeoxynucleotides

    PubMed Central

    Acedo, Montse; Fàbrega, Carme; Aviño, Anna; Goodman, Myron; Fagan, Patricia; Wemmer, David; Eritja, Ramon

    1994-01-01

    The use of the ammonia deprotection step to introduce 15N labels at specific exocyclic amino positions of adenine, cytosine, guanine or 2-aminopurine of oligodeoxynucleotides is described. PMID:8065910

  10. Dimensional accuracy of small gold alloy castings. Part 4. The casting ring and ring liners.

    PubMed

    Morey, E F

    1992-04-01

    The role of the casting ring and its asbestos liner is discussed. Asbestos as a liner has now largely been replaced by two alternative materials, one based on cellulose and the other on ceramic fibres. The limited literature on the effect of these newer materials on casting accuracy is also reviewed as their introduction may require significant changes in the traditional technology of dental casting.

  11. Design consideration for design a flat and ring plastics part using Solidworks software

    NASA Astrophysics Data System (ADS)

    Amran, M. A. M.; Faizal, K. M.; Salleh, M. S.; Sulaiman, M. A.; Mohamad, E.

    2015-12-01

    Various considerations on design of plastic injection moulded parts were applied in initial stage to prevent any defects of end products. Therefore, the objective of this project is to design the plastic injection moulded part by taking consideration on several factors such as draft angle, corner radius and location of gate. In this project, flat plastic part, ring plastic part, core inserts for flat and ring plastic part were designed using SolidWorks software. The plastic part was drawn in sketching mode then the 3D modeling of solid part was generated using various commands. Considerations of plastic part such as draft angle and corner radius with location of gate was considered in the design stage. Finally, it was successfully designed the two plastic parts with their respectively insert by using SolidWorks software. The flat plastic part and ring plastic part were designed for the purpose for future researches for study the weld lines, meld lines, air trapped and geometrical size of the product. Thus, by designing the flat plastic part and ring plastic part having core insert on each part, the completed mould design of two plate mould can be considered. This is because, plastic injection parts are needed to be designed properly in order to neglect any defect when the mould was made.

  12. Dicamba Monooxygenase: Structural Insights into a Dynamic Rieske Oxygenase that Catalyzes an Exocyclic Monooxygenation

    SciTech Connect

    D'Ordine, Robert L.; Rydel, Timothy J.; Storek, Michael J.; Sturman, Eric J.; Moshiri, Farhad; Bartlett, Ryan K.; Brown, Gregory R.; Eilers, Robert J.; Dart, Crystal; Qi, Youlin; Flasinski, Stanislaw; Franklin, Sonya J.

    2009-09-08

    Dicamba (2-methoxy-3,6-dichlorobenzoic acid) O-demethylase (DMO) is the terminal Rieske oxygenase of a three-component system that includes a ferredoxin and a reductase. It catalyzes the NADH-dependent oxidative demethylation of the broad leaf herbicide dicamba. DMO represents the first crystal structure of a Rieske non-heme iron oxygenase that performs an exocyclic monooxygenation, incorporating O{sub 2} into a side-chain moiety and not a ring system. The structure reveals a 3-fold symmetric trimer ({alpha}{sub 3}) in the crystallographic asymmetric unit with similar arrangement of neighboring inter-subunit Rieske domain and non-heme iron site enabling electron transport consistent with other structurally characterized Rieske oxygenases. While the Rieske domain is similar, differences are observed in the catalytic domain, which is smaller in sequence length than those described previously, yet possessing an active-site cavity of larger volume when compared to oxygenases with larger substrates. Consistent with the amphipathic substrate, the active site is designed to interact with both the carboxylate and aromatic ring with both key polar and hydrophobic interactions observed. DMO structures were solved with and without substrate (dicamba), product (3,6-dichlorosalicylic acid), and either cobalt or iron in the non-heme iron site. The substitution of cobalt for iron revealed an uncommon mode of non-heme iron binding trapped by the non-catalytic Co{sup 2+}, which, we postulate, may be transiently present in the native enzyme during the catalytic cycle. Thus, we present four DMO structures with resolutions ranging from 1.95 to 2.2 {angstrom}, which, in sum, provide a snapshot of a dynamic enzyme where metal binding and substrate binding are coupled to observed structural changes in the non-heme iron and catalytic sites.

  13. Mechanism of Repair of Acrolein- and Malondialdehyde-Derived Exocyclic Guanine Adducts by the α-Ketoglutarate/Fe(II) Dioxygenase AlkB

    PubMed Central

    2015-01-01

    The structurally related exocyclic guanine adducts α-hydroxypropano-dG (α-OH-PdG), γ-hydroxypropano-dG (γ-OH-PdG), and M1dG are formed when DNA is exposed to the reactive aldehydes acrolein and malondialdehyde (MDA). These lesions are believed to form the basis for the observed cytotoxicity and mutagenicity of acrolein and MDA. In an effort to understand the enzymatic pathways and chemical mechanisms that are involved in the repair of acrolein- and MDA-induced DNA damage, we investigated the ability of the DNA repair enzyme AlkB, an α-ketoglutarate/Fe(II) dependent dioxygenase, to process α-OH-PdG, γ-OH-PdG, and M1dG in both single- and double-stranded DNA contexts. By monitoring the repair reactions using quadrupole time-of-flight (Q-TOF) mass spectrometry, it was established that AlkB can oxidatively dealkylate γ-OH-PdG most efficiently, followed by M1dG and α-OH-PdG. The AlkB repair mechanism involved multiple intermediates and complex, overlapping repair pathways. For example, the three exocyclic guanine adducts were shown to be in equilibrium with open-ring aldehydic forms, which were trapped using (pentafluorobenzyl)hydroxylamine (PFBHA) or NaBH4. AlkB repaired the trapped open-ring form of γ-OH-PdG but not the trapped open-ring of α-OH-PdG. Taken together, this study provides a detailed mechanism by which three-carbon bridge exocyclic guanine adducts can be processed by AlkB and suggests an important role for the AlkB family of dioxygenases in protecting against the deleterious biological consequences of acrolein and MDA. PMID:25157679

  14. Numerical simulation of ring rolling process — Application to superalloy 718 parts

    NASA Astrophysics Data System (ADS)

    Chabin, D.; Emptas, P. Y.; Bouzaiane, M.

    2007-04-01

    Numerical simulation has become a powerful tool that enables to save costs and time in the design and manufacturing of forged parts for aircraft engines. A complete simulation "package" based on the software code Forge® is used at Snecma to predict the properties of such parts and optimize the manufacturing processes. In order to have a good prediction of the metallurgical and mechanical properties, the simulation of the whole forging process is needed. Until now ring rolling simulation tools have been developed but they still need to be improved. Moreover we have to evaluate these tools before bringing them into production. The aim of this paper is to present the work being done at Snecma on ring rolling simulation. An overview of the complete simulation "package" will first be given. Some tests performed with the ring rolling simulation module in Forge® will be presented, including the comparison between simulation results and real parts. The application to an Inconel® 718 disk will be discussed more into details.

  15. Numerical simulation of ring rolling process - Application to superalloy 718 parts

    SciTech Connect

    Chabin, D.; Emptas, P. Y.; Bouzaiane, M.

    2007-04-07

    Numerical simulation has become a powerful tool that enables to save costs and time in the design and manufacturing of forged parts for aircraft engines. A complete simulation 'package' based on the software code Forge is used at Snecma to predict the properties of such parts and optimize the manufacturing processes. In order to have a good prediction of the metallurgical and mechanical properties, the simulation of the whole forging process is needed. Until now ring rolling simulation tools have been developed but they still need to be improved. Moreover we have to evaluate these tools before bringing them into production. The aim of this paper is to present the work being done at Snecma on ring rolling simulation. An overview of the complete simulation 'package' will first be given. Some tests performed with the ring rolling simulation module in Forge will be presented, including the comparison between simulation results and real parts. The application to an Inconel 718 disk will be discussed more into details.

  16. Rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes with substituted allenes: stereoselective construction of tri- and tetrasubstituted exocyclic olefins.

    PubMed

    Evans, P Andrew; Negru, Daniela E; Shang, Deju

    2015-04-13

    The development of the stereoselective rhodium-catalyzed [(3+2)+2] carbocyclization of alkynylidenecyclopropanes (ACPs) with substituted allenes is described. This work demonstrates that activated and unactivated allenes preferentially undergo carbometalation at the distal terminus to generate tri- and tetrasubstituted exocyclic olefins with a neutral rhodium catalyst. In addition, this method provides a strategy for the total synthesis of the guaiane family of sesquiterpenes, which are not directly accessible using alkynes as exogenous π-components. Finally, the preparation of the bicyclo[5.4.0]undecane ring system using a homologated ACP tether serves to further illustrate the versatility of this approach. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Pleuromutilin derivatives having a purine ring. Part 3: synthesis and antibacterial activity of novel compounds possessing a piperazine ring spacer.

    PubMed

    Hirokawa, Yoshimi; Kinoshita, Hironori; Tanaka, Tomoyuki; Nakamura, Takanori; Fujimoto, Koichi; Kashimoto, Shigeki; Kojima, Tsuyoshi; Kato, Shiro

    2009-01-01

    SAR studies on the water-soluble thioether pleuromutilin analogue 6, which has excellent in vitro and in vivo antibacterial activities, led to discovery of the novel pleuromutilin derivatives having a piperazine ring spacer. These derivatives displayed potent and well-balanced in vitro antibacterial activity against various drug-susceptible and -resistant Gram-positive bacteria. In particular, the promising pleuromutilin analogues 37 and 40 were found to exhibit strong in vivo efficacy against Staphylococcus aureus Smith.

  18. Last millennium northern hemisphere summer temperatures from tree rings: Part I: The long term context

    NASA Astrophysics Data System (ADS)

    Wilson, Rob; Anchukaitis, Kevin; Briffa, Keith R.; Büntgen, Ulf; Cook, Edward; D'Arrigo, Rosanne; Davi, Nicole; Esper, Jan; Frank, Dave; Gunnarson, Björn; Hegerl, Gabi; Helama, Samuli; Klesse, Stefan; Krusic, Paul J.; Linderholm, Hans W.; Myglan, Vladimir; Osborn, Timothy J.; Rydval, Miloš; Schneider, Lea; Schurer, Andrew; Wiles, Greg; Zhang, Peng; Zorita, Eduardo

    2016-02-01

    Large-scale millennial length Northern Hemisphere (NH) temperature reconstructions have been progressively improved over the last 20 years as new datasets have been developed. This paper, and its companion (Part II, Anchukaitis et al. in prep), details the latest tree-ring (TR) based NH land air temperature reconstruction from a temporal and spatial perspective. This work is the first product of a consortium called N-TREND (Northern Hemisphere Tree-Ring Network Development) which brings together dendroclimatologists to identify a collective strategy for improving large-scale summer temperature reconstructions. The new reconstruction, N-TREND2015, utilises 54 records, a significant expansion compared with previous TR studies, and yields an improved reconstruction with stronger statistical calibration metrics. N-TREND2015 is relatively insensitive to the compositing method and spatial weighting used and validation metrics indicate that the new record portrays reasonable coherence with large scale summer temperatures and is robust at all time-scales from 918 to 2004 where at least 3 TR records exist from each major continental mass. N-TREND2015 indicates a longer and warmer medieval period (∼900-1170) than portrayed by previous TR NH reconstructions and by the CMIP5 model ensemble, but with better overall agreement between records for the last 600 years. Future dendroclimatic projects should focus on developing new long records from data-sparse regions such as North America and eastern Eurasia as well as ensuring the measurement of parameters related to latewood density to complement ring-width records which can improve local based calibration substantially.

  19. Eigen analysis of tree-ring records: Part 1, a limited representativeness of regional curve

    NASA Astrophysics Data System (ADS)

    Yang, Bao; Sonechkin, Dmitry M.; Datsenko, Nina M.; Ivashchenko, Nadezda N.; Liu, Jingjing; Qin, Chun

    2011-12-01

    Based on a set of very long-living (2,000 years) Qilian junipers ( Sabina przewalskii Kom.) from the north-eastern part of the Tibetan Plateau (the region of Dulan), we carefully consider the regional curve standardization (RCS) technique. For this goal, we correlate deviations of individual tree-ring width records from their regional mean age-dependent curve (RC). It turns out that these correlations keep their positivity for almost all shifts between ages compared (up to 500 years and even more) evidencing each Dulan juniper to be a unique "thermometer". Just the unification of these "thermometers" in the form RC creates a spurious positive trend in the Dulan chronology. We modify the RCS technique to closer attach RC to these "thermometers" in order to construct a new chronology in which the trend is absent.

  20. Aminopropanedinitrile (aminomalononitrile, AMN) in the synthesis of C-nucleosides and exocyclic amino thiazole N-nucleosides. Formation and reactions of 2-substituted-5-amino-4-oxazolecarbonitriles

    SciTech Connect

    Scheuerman, R.A.

    1992-01-01

    Aminopropanedinitrile (aminomalononitrile, AMN) reacts with a wide variety of alkyl, aryl, or heteroaryl acid chlorides in the presence of 1-methyl-2-pyrrolidinone to give N-(dicyanomethyl)carboxamides which are easily cyclized in situ or after isolation to 2-substituted-5-amino-4-oxazolecarbonitriles in good to excellent yields. Electron attracting or electron releasing groups on the phenyl rings do not appear to greatly influence the yields of oxazoles and steric factors do not appear to be important in the aliphatic series. The reaction of 2, 5-anhydro-3, 4, 6-tri-O-benzoyl-[beta]-D-allonyl chloride with aminopropane-dinitrile gives 2, 5-anhydro-N-(dicyanomethyl)-[beta]-D-allonamide-3, 4, 6-tribenzoate which is converted to 5-amino-2-(2, 3, 5-tri-O-benzoyl-[beta]-D-ribofuranosyl)-4-oxazolecarbonitrile, which is used to prepare other C-nucleosides including 2-([beta]-D-ribofuranosyl)oxazole-4-carboxamide (oxazofurin), an analogue of the antitumor and antiviral C-nucleoside tiazofurin. Attempted deblocking of several benzoyl protected C-nucleosides with sodium methoxide led to double elimination reactions and the formation of furan derivatives. The 2-substituted-5-amino-4-oxazolecarbonitriles react with ortho esters to give imidates which are cyclized to axazolo[5,4-d]pyrimidines. Reactions of 2-substituted-5-amino-4-oxazolecarbonitriles include acylation of the 5-amino group, dediazotization of the 5-amino group, nucleophilic attack and ring opening of the oxazole, and acid catalyzed ring opening of the oxazole. Sugar isothiocyanates are prepared and react with aminopropane-dinitrile (aminomalononitrile, AMN) in the presence of 1-methyl-2-pyrrolidinone to afford exocyclic amino thiazole N-nucleosides.

  1. Exocyclic Deoxyadenosine Adducts of 1,2,3,4-Diepoxybutane: Synthesis, Structural Elucidation, and Mechanistic Studies

    PubMed Central

    Seneviratne, Uthpala; Antsypovich, Sergey; Goggin, Melissa; Dorr, Danae Quirk; Guza, Rebecca; Moser, Adam; Thompson, Carrie; York, Darrin M.; Tretyakova, Natalia

    2009-01-01

    1,2,3,4-Diepoxybutane (DEB)1 is considered the ultimate carcinogenic metabolite of 1,3-butadiene, an important industrial chemical and environmental pollutant present in urban air. Although it preferentially modifies guanine within DNA, DEB induces a large number of A → T transversions, suggesting that it forms strongly mispairing lesions at adenine nucleobases. We now report the discovery of three potentially mispairing exocyclic adenine lesions of DEB: N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2′-deoxyadenosine (compound 2), 1,N6-(2-hydroxy-3-hydroxymethylpropan-1,3-diyl)-2′-deoxyadenosine (compound 3), and 1,N6-(1-hydroxymethyl-2-hydroxypropan-1,3-diyl)-2′-deoxyadenosine (compound 4). The structures and stereochemistry of the novel DEB-dA adducts were determined by a combination of UV and NMR spectroscopy, tandem mass spectrometry, and independent synthesis. We found that synthetic N6-(2-hydroxy-3,4-epoxybut-1-yl)-2′-deoxyadenosine (compound 1) representing the product of N6-adenine alkylation by DEB spontaneously cyclizes to form 3 under aqueous conditions or 2 under anhydrous conditions in the presence of organic base. Compound 3 can be interconverted with 4 by a reversible unimolecular pericyclic reaction favoring 4 as a more thermodynamically stable product. Both 3 and 4 are present in double stranded DNA treated with DEB in vitro and in liver DNA of laboratory mice exposed to 1,3-butadiene by inhalation. We propose that in DNA under physiological conditions, DEB alkylates the N-1 position of adenine in DNA to form N1-(2-hydroxy-3,4-epoxybut-1-yl)-adenine adducts, which undergo an SN2-type intramolecular nucleophilic substitution and rearrangement to give 3 (minor) and 4 (major). Formation of exocyclic DEB-adenine lesions following exposure to 1,3-butadiene provides a possible mechanism of mutagenesis at the A:T base pairs. PMID:19883087

  2. THREE-DIMENSIONAL DUST MAPPING REVEALS THAT ORION FORMS PART OF A LARGE RING OF DUST

    SciTech Connect

    Schlafly, E. F.; Rix, H.-W.; Martin, N. F.; Green, G.; Finkbeiner, D. P.; Burgett, W. S.; Chambers, K. C.; Kaiser, N.; Morgan, J. S.; Tonry, J. L.; Wainscoat, R. J.; Waters, C.; Draper, P. W.; Metcalfe, N.; Price, P. A.

    2015-02-01

    The Orion Molecular Complex is the nearest site of ongoing high-mass star formation, making it one of the most extensively studied molecular complexes in the Galaxy. We have developed a new technique for mapping the three-dimensional distribution of dust in the Galaxy using Pan-STARRS1 photometry. We isolate the dust at the distance to Orion using this technique, revealing a large (100 pc, 14° diameter), previously unrecognized ring of dust, which we term the ''Orion dust ring''. The ring includes Orion A and B, and is not coincident with current Hα features. The circular morphology suggests formation as an ancient bubble in the interstellar medium, though we have not been able to conclusively identify the source of the bubble. This hint at the history of Orion may have important consequences for models of high-mass star formation and triggered star formation.

  3. Luttinger liquid theory of Coulomb drag in mesoscopic rings,(Supported in part by US DOE.)

    NASA Astrophysics Data System (ADS)

    Shahbazyan, T. V.; Ulloa, S. E.

    1997-03-01

    We develop a Luttinger liquid theory of the Coulomb drag of persistent currents, flowing in concentric mesoscopic rings, by incorporating non-linear corrections to the electron dispersion relation. We demonstrate that at low temperatures interactions between electrons in different rings generate an additional phase and thus alter the period of Aharonov-Bohm oscillations. The resulting nondissipative(A. G. Rojo and G. D. Mahan, Phys. Rev. Lett. 68) 2074 (1992). drag depends strongly on the relative parity of the electron numbers. We also show that interactions set a new temperature scale below which the linear response theory does not apply at certain values of external flux.

  4. Synthesis and properties of novel 2'-C,4'-C-ethyleneoxy-bridged 2'-deoxyribonucleic acids with exocyclic methylene groups.

    PubMed

    Osawa, Takashi; Obika, Satoshi; Hari, Yoshiyuki

    2016-10-12

    Three 2'-C,4'-C-ethyleneoxy-bridged 2'-deoxyribonucleic acids possessing six-membered bridges with 6'-oxygen and 8'-exocyclic methylene groups (methylene-EoDNAs) were designed and synthesized in nine to ten steps from 5-methyluridine. The methylene-EoDNA-modified oligonucleotides showed excellent binding affinity with target ssRNA and extremely high nuclease resistance compared with natural oligonucleotides. These results proved the potential of methylene-EoDNAs for nucleic acid based technology.

  5. Purine (N)-Methanocarba Nucleoside Derivatives Lacking an Exocyclic Amine as Selective A3 Adenosine Receptor Agonists

    PubMed Central

    2016-01-01

    Purine (N)-methanocarba-5′-N-alkyluronamidoriboside A3 adenosine receptor (A3AR) agonists lacking an exocyclic amine resulted from an unexpected reaction during a Sonogashira coupling and subsequent aminolysis. Because the initial C6-Me and C6-styryl derivatives had unexpectedly high A3AR affinity, other rigid nucleoside analogues lacking an exocyclic amine were prepared. Of these, the C6-Me-(2-phenylethynyl) and C2-(5-chlorothienylethynyl) analogues were particularly potent, with human A3AR Ki values of 6 and 42 nM, respectively. Additionally, the C2-(5-chlorothienyl)-6-H analogue was potent and selective at A3AR (MRS7220, Ki 60 nM) and also completely reversed mouse sciatic nerve mechanoallodynia (in vivo, 3 μmol/kg, po). The lack of a C6 H-bond donor while maintaining A3AR affinity and efficacy could be rationalized by homology modeling and docking of these hypermodified nucleosides. The modeling suggests that a suitable combination of stabilizing features can partially compensate for the lack of an exocyclic amine, an otherwise important contributor to recognition in the A3AR binding site. PMID:26890707

  6. An investigation of volcanic depressions. Part 3: Maars, tuff-rings, tuff-cones, and diatremes

    NASA Technical Reports Server (NTRS)

    Lorenz, V.; Mcbirney, A. R.; Williams, H.

    1970-01-01

    A classification of maars, tuff-rings, tuff-cones, and diatremes is given along with a summary of their lithologic and structural characteristics at the surface and at depth, and their probable manner of formation. Particular emphasis is placed on the roles of fluidization and groundwater.

  7. Porphyrins with exocyclic rings. 15.(1) synthesis of quino- and isoquinoporphyrins, aza analogues of the naphthoporphyrins.

    PubMed

    Lash, T D; Gandhi, V

    2000-11-17

    Porphyrins with fused isoquinoline and quinoline units have been prepared by the "3 + 1" methodology. 5-Nitroisoquinoline and 6-nitroquinoline condensed with ethyl isocyanoacetate in the presence of a phosphazene base to give isoquino- and quinopyrroles, respectively. Ester saponification and decarboxylation with KOH in ethylene glycol at 190 degrees C gave the parent azatricycles, and these were further condensed with 2 equiv of an acetoxymethylpyrrole to give the corresponding tripyrranes protected at the terminal positions as their tert-butyl esters. In a one-pot procedure, the ester protective groups were cleaved with TFA, and following dilution with dichloromethane, "3 + 1" condensation with a pyrrole dialdehyde and dehydrogenation of the phlorin intermediate with DDQ gave the targeted azanaphthoporphyrins in excellent yields. Although the UV-vis spectra of these new porphyrin systems are unexceptional, they show promise for further functionalization and applications in the development of porphyrin arrays. In addition, a zinc chelate of the isoquinoporphyrin system shows a high degree of regioselective intermolecular interaction/aggregation in chloroform solution that may lead to selectivity in molecular recognition studies.

  8. Eigen analysis of tree-ring records: part 2, posing the eigen problem

    NASA Astrophysics Data System (ADS)

    Yang, Bao; Sonechkin, Dmitry M.; Datsenko, Nina M.; Ivashchenko, Nadezda N.; Liu, Jingjing; Qin, Chun

    2012-01-01

    The technique of expanding meteorological fields on eigenvectors of the field covariation matrix is popular. In this paper, we propose for the first time to use a mathematically similar technique to solve the main problem of dendrochronology: classifying variations in tree-ring records as either age- and microenvironment-dependent or climate-induced. Applying this technique to a sample of very long-lived Qilian junipers ( Sabina przewalskii Kom.) from the Dulan region in western China, we demonstrate that the ring-width variations projected on the first eigenvector are age-dependent, but those projected on several of the first subsequent vectors are mainly climate-induced. In particular, the second and third projections capture multi-centennial climatic variations, and the variations projected on the fourth through seventh eigenvectors show periodic variations that are probably induced by the 178-year solar cycle. The projections on the smallest eigenvectors seem to be negligible.

  9. Eigen analysis of tree-ring records: part 3, taking heteroscedasticity and sampling effects into consideration

    NASA Astrophysics Data System (ADS)

    Yang, Bao; Sonechkin, Dmitry M.; Datsenko, Nina M.; Ivashchenko, Nadezda N.; Liu, Jingjing; Qin, Chun

    2012-02-01

    This paper reports on the further development of a new technique for standardization of tree-ring records called the eigen analysis of tree-ring records. The data are from the same sample set of 56 long-lived Qilian junipers ( Sabina przewalskii Kom.) from the Dulan region in western China as was used in our previous paper (Yang et al. 2011b). To assess the heteroscedasticity of individual record deviations from the sample set regional curve (RC), we tested five different definitions of those deviations. Direct computations of eigenvectors of all relevant intrarecord covariation matrices turned out to be greatly affected by observational and computational noise; an analytic approximation of these vectors was therefore desirable. The Bessel function of the first kind and the zero order proved suitable for such an approximation, especially because the deviations were defined via subtraction of the RC from raw ring width records. Exclusion of the contributions of the first segment of the Bessel approximation, corresponding to the extremely large first eigenvalue, rendered individual record deviations from RC homoscedastic. Therefore, the routine Fourier basis became applicable to extract climate-dependent components of the residual deviations. A Fourier expansion of the Dulan chronology revealed the quasi-200-year-long solar activity cycle to be the main factor affecting Dulan tree growth.

  10. Influence of ring size on the cognition-enhancing activity of DM235 and MN19, two potent nootropic drugs.

    PubMed

    Guandalini, L; Martini, E; Di Cesare Mannelli, L; Dei, S; Manetti, D; Scapecchi, S; Teodori, E; Ghelardini, C; Romanelli, M N

    2012-03-01

    A series of analogs of DM235 and MN19, characterized by rings with different size, have been prepared and evaluated for their nootropic activity in the mouse passive-avoidance test. It was found that the optimal ring size for the analogs of DM235, showing endocyclic both amidic groups, is 6 or 7 atoms. For the compounds structurally related to MN19, carrying an exocyclic amide group, the piperidine ring is the moiety which gives the most interesting compounds.

  11. Surfaces, atmospheres and magnetospheres of the outer planets and their satellites and ring systems: Part X

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Atreya, S.; Castillo, J.; Coll, P.; Mueller-Wodarg, I.; Spilker, L.

    2014-12-01

    This issue contains research work presented during the past year in sessions organized at several international meetings and congresses (such as those of the European Geosciences Union (EGU), the Asia Oceania Geosciences Society (AOGS), the European Planetary Science Congress (EPSC) and others) and focusing on recent observations and models of the atmospheres, magnetospheres and surfaces of the giant planets and their satellites, as well as on their ring systems. Particular attention was devoted this time to the proposals for exploration of the Solar System by spacecraft and probes submitted during the ESA call for science themes for the L2 and L3 missions in 2013.

  12. Mineralization in the Uyaijah-Thaaban area, west-central part of the Uyaijah ring structure, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Dodge, F.C.; Helaby, A.M.

    1975-01-01

    Anomalous amounts of tungsten, molybdenum, and bismuth were found previously in surficial debris collected from the Uyaijah-Thaaban area in the west-central part of the Precambrian Al Uyaijah ring structure. The area is mostly underlain by quartz monzonite. Countless quartz veins ranging from a knife edge to more than 3 m in thickness cut the quartz monzonite; many of these veins contain molybdenite. Detailed mapping and intensive sampling of the molybdenite-bearing quartz veins indicate that their grade and quantity are probably inadequate to permit present-day mining; however, they represent a potential future resource. The tungsten of the area appears to be negligible.

  13. Last millennium Northern Hemisphere summer temperatures from tree rings: Part II, spatially resolved reconstructions

    NASA Astrophysics Data System (ADS)

    Anchukaitis, Kevin J.; Wilson, Rob; Briffa, Keith R.; Büntgen, Ulf; Cook, Edward R.; D'Arrigo, Rosanne; Davi, Nicole; Esper, Jan; Frank, David; Gunnarson, Björn E.; Hegerl, Gabi; Helama, Samuli; Klesse, Stefan; Krusic, Paul J.; Linderholm, Hans W.; Myglan, Vladimir; Osborn, Timothy J.; Zhang, Peng; Rydval, Milos; Schneider, Lea; Schurer, Andrew; Wiles, Greg; Zorita, Eduardo

    2017-05-01

    Climate field reconstructions from networks of tree-ring proxy data can be used to characterize regional-scale climate changes, reveal spatial anomaly patterns associated with atmospheric circulation changes, radiative forcing, and large-scale modes of ocean-atmosphere variability, and provide spatiotemporal targets for climate model comparison and evaluation. Here we use a multiproxy network of tree-ring chronologies to reconstruct spatially resolved warm season (May-August) mean temperatures across the extratropical Northern Hemisphere (40-90°N) using Point-by-Point Regression (PPR). The resulting annual maps of temperature anomalies (750-1988 CE) reveal a consistent imprint of volcanism, with 96% of reconstructed grid points experiencing colder conditions following eruptions. Solar influences are detected at the bicentennial (de Vries) frequency, although at other time scales the influence of insolation variability is weak. Approximately 90% of reconstructed grid points show warmer temperatures during the Medieval Climate Anomaly when compared to the Little Ice Age, although the magnitude varies spatially across the hemisphere. Estimates of field reconstruction skill through time and over space can guide future temporal extension and spatial expansion of the proxy network.

  14. Synthesis and Iron Sequestration Equilibria of Novel Exocyclic 3-Hydroxy-2-pyridinone Donor Group Siderophore Mimics

    PubMed Central

    Harrington, James M.; Chittamuru, Sumathi; Dhungana, Suraj; Jacobs, Hollie K.; Gopalan, Aravamudan S.; Crumbliss, Alvin L.

    2011-01-01

    The synthesis of a novel class of exocyclic bis- and tris-3,2-hydroxypyridinone (HOPO) chelators built on N2 and N3 aza-macrocyclic scaffolds and the thermodynamic solution characterization of their complexes with Fe(III) are described. The chelators for this study were prepared by reaction of either piperazine or N, N’, N”-1,4,7-triazacyclononane with a novel electrophilic HOPO iminium salt in good yields. Subsequent removal of the benzyl protecting groups using hydrogenolysis gave bis-HOPO chelators N2(etLH)2 and N2(prLH)2, and tris-HOPO chelator N3(etLH)3 in excellent yields. Solution thermodynamic characterization of their complexes with Fe(III) has been accomplished using spectrophotometric, potentiometric and ESI-MS methods. The pKas of N2(etLH)2, N2(prLH)2, and N3(etLH)3, were determined spectrophotometrically and potentiometrically. The Fe(III) complex stability constants for the tetradentate N2(etLH)2 and N2(prLH)2, and hexadentate N3(etLH)3, were measured by spectrophotometric and potentiometric titration, and by competition with EDTA. N3(etLH)3 forms a 1:1 complex with Fe(III) with log β110 = 27.34 ± 0.04. N2(prLH)2 forms a 3:2 L:Fe complex with Fe(III) where log β230 = 60.46 ± 0.04 and log β110 = 20.39 ± 0.02. While N2(etLH)2 also forms a 3:2 L:Fe complex with Fe(III), solubility problems precluded determining log β230; log β110 was found to be 20.45 ± 0.04. The pFe values of 26.5 for N3(etLH)3 and 24.78 for N2(prLH)2 are comparable to other siderophore molecules used in the treatment of iron overload, suggesting that these hydroxypyridinone ligands may be useful in the development of new chelation therapy agents. PMID:20715813

  15. Aryldiones incorporating a [1,4,5]oxadiazepane ring. Part I: Discovery of the novel cereal herbicide pinoxaden.

    PubMed

    Muehlebach, Michel; Boeger, Manfred; Cederbaum, Fredrik; Cornes, Derek; Friedmann, Adrian A; Glock, Jutta; Niderman, Thierry; Stoller, André; Wagner, Trixie

    2009-06-15

    Derivatives of the new class of 3-hydroxy-4-phenyl-5-oxo-pyrazolines were optimized towards both herbicidal activity on key annual grass weed species and selectivity in small grain cereal crops. The generic structure can be separated into three parts for the analysis of the structure-activity relationships, namely the aryl, the dione with its prodrug forms and the hydrazine moiety. Each area appears to play distinct and different roles in overall expression of biological performance which is further beneficially influenced by adjuvant response and safener action. Pinoxaden 6, a novel graminicide for use in wheat and barley incorporating a [1,4,5]oxadiazepane ring, eventually emerged as a development candidate from the discovery and optimization process.

  16. Aryldiones incorporating a [1,4,5]oxadiazepane ring. Part 2: chemistry and biology of the cereal herbicide pinoxaden.

    PubMed

    Muehlebach, Michel; Cederbaum, Fredrik; Cornes, Derek; Friedmann, Adrian A; Glock, Jutta; Hall, Gavin; Indolese, Adriano F; Kloer, Daniel P; Le Goupil, Gael; Maetzke, Thomas; Meier, Hans; Schneider, Rudolf; Stoller, André; Szczepanski, Henry; Wendeborn, Sebastian; Widmer, Hansjuerg

    2011-12-01

    Pinoxaden is a new cereal herbicide that provides outstanding levels of post-emergence activity against a broad spectrum of grass weed species for worldwide selective use in both wheat and barley. Factors influencing activity and tolerance to pinoxaden were in part linked to distinct structural parts of the active ingredient. Three complementary contributions that decisively impact upon the herbicidal potency against grasses were identified: a preferred 2,6-diethyl-4-methyl aromatic substitution pattern, a dione area suitable for proherbicide formation and beneficial adjuvant effects. The uptake and translocation pattern of pinoxaden when coapplied with its tailored adjuvant were analysed by autoradiography, indicating extensive and rapid penetration, followed by effective distribution throughout the plant. Crop injury reduction on incorporation of the [1,4,5]oxadiazepane ring into the aryldione template was reinforced with safener technology. Comparative studies on the behaviour of pinoxaden applied either alone or in combination with the safener cloquintocet-mexyl demonstrated that addition of the safener resulted in significant enhancement of metabolic degradation in wheat and barley, providing excellent crop tolerance and a substantial selectivity margin without adverse effects on weed control. The biological potential of pinoxaden and its active principle pinoxaden dione in terms of grass weed control and tolerance in cereals was fully exploited by inclusion of the safener cloquintocet-mexyl in the formulation in combination with a specific and tailor-made tank-mix adjuvant based on methylated rape seed oil. Copyright © 2011 Society of Chemical Industry.

  17. Rings Through Atmosphere

    NASA Image and Video Library

    2010-05-26

    NASA Cassini spacecraft looks toward the limb of Saturn and, on the right of this image, views part of the rings through the planet atmosphere. Saturn atmosphere can distort the view of the rings from some angles.

  18. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry

    2014-03-01

    Preface: a personal view of planetary rings; 1. Introduction: the allure of the ringed planets; 2. Studies of planetary rings 1610-2013; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Uranus' rings and moons; 13. Neptune's partial rings; 14. Jupiter's ring-moon system after Galileo and New Horizons; 15. Ring photometry; 16. Dusty rings; 17. Concluding remarks; Afterword; Glossary; References; Index.

  19. Application of the Green's function method to some nonlinear problems of an electron storage ring. Part III. Beam-size enhancement due to the presence of nonlinear magnets in a ring

    SciTech Connect

    Kheifets, S.

    1983-01-01

    A perturbation method which allows one to find the distribution function and the beam size for a broad class of storage ring nonlinear problems is described in Part I of this work. In present note I apply this method to a particular problem. Namely, I want to evaluate an enhancement of the vertical beam size of a bunch due to the presence of the ring of nonlinear magnetic fields. The main part of the work deals with sextupole magnets. Formula for the beam size in the presence of octupole fields are also developed to the first order in the octupole strength, although octupole magnets are not widely used in present storage ring designs. This calculation is done mainly because the octupole field has the same symmetry as the beam-beam force for the head-on collision. This will give us the opportunity to compare the conduct of the bunch due to this two types of nonlinear kicks. The general terms of the applicability of the Green's function method is discussed in the first part of this work.

  20. Methyl [13C]glucopyranosiduronic acids: effect of COOH ionization and exocyclic structure on NMR spin-couplings.

    PubMed

    Zhang, Wenhui; Hu, Xiaosong; Carmichael, Ian; Serianni, Anthony S

    2012-11-02

    Methyl α- and β-D-glucopyranuronides singly labeled with (13)C at C1-C6 were prepared from the corresponding (13)C-labeled methyl D-glucopyranosides, and multiple NMR J-couplings (J(HH), J(CH), and J(CC)) were measured in their protonated and ionized forms in aqueous ((2)H(2)O) solution. Solvated density functional theory (DFT) calculations of J-couplings in structurally related model compounds were performed to determine how well the calculated J-couplings matched the experimental values in saccharides bearing an ionizable substituent. Intraring J(HH) values in both uronide anomers, including (3)J(H4,H5), are unaffected by solution pD, and COOH ionization exerts little effect on J(CH) and J(CC) except for (1)J(C1,H1), (1)J(C4,H4), (1)J(C5,H5), (1)J(C5,C6), and (2)J(C3,C5), where changes of up to 5 Hz were observed. Some of these changes are associated with changes in bond lengths upon ionization; in general, better agreement between theory and experiment was observed for couplings less sensitive to exocyclic C-O bond conformation. Titration of (1)H and (13)C chemical shifts, and some J-couplings, yielded a COOH pK(a) of 3.0 ± 0.1 in both anomers. DFT calculations suggest that substituents proximal to the exocyclic COOH group (i.e., the C4-O4 bond) influence the activation barrier to C5-C6 bond rotation due to transient intramolecular H-bonding. A comparison of J-couplings in the glucopyranuronides to corresponding J-couplings in the glucopyranosides showed that more pervasive changes occur upon conversion from a COOH to a CH(2)OH substituent at C6 than from COOH ionization within the uronides. Twelve J-couplings are affected, with the largest being (1)J(C5,C6) (∼18 Hz larger in the uronides), followed by (2)J(C6,H5) (∼2.5 Hz more negative in the uronides).

  1. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2011-07-01

    Preface; 1. Introduction: the allure of ringed planets; 2. Studies of planetary rings 1610-2004; 3. Diversity of planetary rings; 4. Individual ring particles and their collisions; 5. Large-scale ring evolution; 6. Moons confine and sculpt rings; 7. Explaining ring phenomena; 8. N-Body simulations; 9. Stochastic models; 10. Age and evolution of rings; 11. Saturn's mysterious F ring; 12. Neptune's partial rings; 13. Jupiter's ring-moon system after Galileo; 14. Ring photometry; 15. Dusty rings; 16. Cassini observations; 17. Summary: the big questions; Glossary; References; Index.

  2. Luminescent Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This view shows the unlit face of Saturn's rings, visible via scattered and transmitted light. In these views, dark regions represent gaps and areas of higher particle densities, while brighter regions are filled with less dense concentrations of ring particles.

    The dim right side of the image contains nearly the entire C ring. The brighter region in the middle is the inner B ring, while the darkest part represents the dense outer B Ring. The Cassini Division and the innermost part of the A ring are at the upper-left.

    Saturn's shadow carves a dark triangle out of the lower right corner of this image.

    The image was taken in visible light with the Cassini spacecraft wide-angle camera on June 8, 2005, at a distance of approximately 433,000 kilometers (269,000 miles) from Saturn. The image scale is 22 kilometers (14 miles) per pixel.

    The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

    For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

  3. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  4. The Jumping Ring Experiment

    ERIC Educational Resources Information Center

    Baylie, M.; Ford, P. J.; Mathlin, G. P.; Palmer, C.

    2009-01-01

    The jumping ring experiment has become central to liquid nitrogen shows given as part of the outreach and open day activities carried out within the University of Bath. The basic principles of the experiment are described as well as the effect of changing the geometry of the rings and their metallurgical state. In general, aluminium rings are…

  5. Asymmetric phase-transfer-catalyzed conjugate addition of glycine imine to exocyclic α,β-unsaturated ketones: construction of polycyclic imines containing three stereocenters.

    PubMed

    Nie, Jing; Hua, Ming-Qing; Xiong, Heng-Ying; Zheng, Yan; Ma, Jun-An

    2012-05-04

    We developed a facile, one-pot, multistep transformation between glycine imine and exocyclic α,β-unsaturated ketones in reactions catalyzed by chiral phase-transfer catalysts (PTC). A series of polycyclic imines containing three adjacent stereocenters were obtained in good to high yields with high diastereo- and enantioselectivities. Further transformation of the imines could afford N-fused polycyclic compounds with four adjacent stereocenters.

  6. Synthesis of Benzo[c]silole Derivatives Bearing a Tetrasubstituted Exocyclic C=C Double Bond by Palladium-Catalyzed Domino Reactions.

    PubMed

    Wagner, Patrick; Gulea, Mihaela; Suffert, Jean; Donnard, Morgan

    2017-06-01

    The synthesis of diversely substituted 2,3-dihydro-benzo[c]siloles through an unprecedented palladium-catalyzed domino sequence is reported, involving a cyclocarbopalladation of an internal silylalkyne. This reaction proceeds with complete stereoselectivity to lead to a fully substituted exocyclic C=C double bond. Notably, the overall domino sequence appears to be crucial to obtain the desired cyclic vinylsilanes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. An Exocyclic Methylene Group Acts As A Bio-isostere of the 2’-Oxygen Atom in LNA

    PubMed Central

    Seth, Punit P; Allerson, Charles R.; Berdeja, Andres; Siwkowski, Andrew; Pallan, Pradeep S.; Gaus, Hans; Prakash, Thazha P.; Watt, Andrew T.; Egli, Martin; Swayze, Eric E.

    2010-01-01

    We show for the first time that it is possible to obtain LNA (Locked Nucleic Acid 1) like binding affinity and biological activity with carbocyclic LNA (cLNA) analogs by replacing the 2’-oxygen atom in LNA with an exocyclic methylene group. Synthesis of the methylene-cLNA nucleoside was accomplished by an intramolecular cyclization reaction between a radical at the 2’-position and a propynyl group at C-4’ position. Only methylene-cLNA modified oligonucleotides showed similar thermal stability and mismatch discrimination properties for complementary nucleic acids as LNA. In contrast, the close structurally related methyl-cLNA analogs showed diminished hybridization properties. Analysis of crystal structures of cLNA modified self-complementary DNA decamer duplexes revealed that the methylene group participates in a tight interaction with a 2’-deoxyribose residue of the 5’-terminal G of a neighboring duplex, resulting in the formation of a CH…O type hydrogen bond. This indicates that the methylene group retains a negative polarization at the edge of the minor groove in the absence of a hydrophilic 2’-substituent and provides a rationale for the superior thermal stability of this modification. In animal experiments, methylene-cLNA ASOs showed similar in vivo activity but reduced toxicity as compared to LNA ASOs. Our work highlights the interchangeable role of oxygen and unsaturated moeities in nucleic acid structure and emphasizes greater use of this bio-isostere to improve the properties of nucleic acids for therapeutic and diagnostic applications. PMID:20886816

  8. An Exocyclic Methylene Group Acts As a Bioisostere of the 2′-Oxygen Atom in LNA

    SciTech Connect

    Seth, Punit P.; Allerson, Charles R.; Berdeja, Andres; Siwkowski, Andrew; Pallan, Pradeep S.; Gaus, Hans; Prakash, Thazha P.; Watt, Andrew T.; Egli, Martin; Swayze, Eric E.

    2010-12-07

    We show for the first time that it is possible to obtain LNA-like (Locked Nucleic Acid 1) binding affinity and biological activity with carbocyclic LNA (cLNA) analogs by replacing the 2{prime}-oxygen atom in LNA with an exocyclic methylene group. Synthesis of the methylene-cLNA nucleoside was accomplished by an intramolecular cyclization reaction between a radical at the 2{prime}-position and a propynyl group at the C-4{prime} position. Only methylene-cLNA modified oligonucleotides showed similar thermal stability and mismatch discrimination properties for complementary nucleic acids as LNA. In contrast, the close structurally related methyl-cLNA analogs showed diminished hybridization properties. Analysis of crystal structures of cLNA modified self-complementary DNA decamer duplexes revealed that the methylene group participates in a tight interaction with a 2{prime}-deoxyribose residue of the 5{prime}-terminal G of a neighboring duplex, resulting in the formation of a CH...O type hydrogen bond. This indicates that the methylene group retains a negative polarization at the edge of the minor groove in the absence of a hydrophilic 2{prime}-substituent and provides a rationale for the superior thermal stability of this modification. In animal experiments, methylene-cLNA antisense oligonucleotides (ASOs) showed similar in vivo activity but reduced toxicity as compared to LNA ASOs. Our work highlights the interchangeable role of oxygen and unsaturated moieties in nucleic acid structure and emphasizes greater use of this bioisostere to improve the properties of nucleic acids for therapeutic and diagnostic applications.

  9. Pleuromutilin derivatives having a purine ring. Part 1: new compounds with promising antibacterial activity against resistant Gram-positive pathogens.

    PubMed

    Hirokawa, Yoshimi; Kinoshita, Hironori; Tanaka, Tomoyuki; Nakamura, Takanori; Fujimoto, Koichi; Kashimoto, Shigeki; Kojima, Tsuyoshi; Kato, Shiro

    2008-06-15

    In the course of our research aimed at the discovery of metabolic stable pleuromutilin derivatives with more potent antibacterial activity against Gram-positive pathogens than previous analogues, a series of compounds bearing a purine ring were prepared and evaluated. From SAR studies, we identified two promising compounds 85 and 87, which have excellent in vitro activity against a number of Gram-positive pathogens, including existing drug-resistant strains, and potent in vivo efficacy.

  10. Synthesis and hybridization property of a boat-shaped pyranosyl nucleic acid containing an exocyclic methylene group in the sugar moiety.

    PubMed

    Mori, Kazuto; Kodama, Tetsuya; Obika, Satoshi

    2015-01-01

    A boat-shaped pyranosyl nucleic acid (BsNA) having an exocyclic methylene group in the sugar moiety was synthesized to investigate the possibility that the axial H3' of original BsNA is the cause of its duplex destabilization. The synthesized BsNA analog was chemically stable against various nucleophiles. From the thermal stability of duplex oligonucleotides including the BsNA analog, it was found that the duplex-forming ability can be sensitive to the size of functional groups at the 3'-position.

  11. Mechanistic and computational studies of exocyclic stereocontrol in the synthesis of bryostatin-like cis-2,6-disubstituted 4-alkylidenetetrahydropyrans by Prins cyclization.

    PubMed

    Ogawa, Yasuyuki; Painter, Phillip P; Tantillo, Dean J; Wender, Paul A

    2013-01-04

    The Prins cyclization of syn-β-hydroxy allylsilanes and aldehydes gives cis-2,6-disubstituted 4-alkylidenetetrahydropyrans as sole products in excellent yields regardless of the aldehyde (R″) or syn-β-hydroxy allylsilane substituent (R') used. By reversing the R″ and R' groups, complementary exocyclic stereocontrol can be achieved. When the anti-β-hydroxy allylsilanes are used, the Prins cyclization gives predominantly cis-2,6-disubstituted 4-alkylidenetetrahydropyrans, now with the opposite olefin geometry in excellent yield. The proposed reaction mechanism and the observed stereoselectivity for these processes are supported by DFT calculations.

  12. Radioactive gold ring dermatitis

    SciTech Connect

    Miller, R.A.; Aldrich, J.E. )

    1990-08-01

    A superficial squamous cell carcinoma developed in a woman who wore a radioactive gold ring for more than 30 years. Only part of the ring was radioactive. Radiation dose measurements indicated that the dose to basal skin layer was 2.4 Gy (240 rad) per week. If it is assumed that the woman continually wore her wedding ring for 37 years since purchase, she would have received a maximum dose of approximately 4600 Gy.

  13. Inner B Ring Terminus

    NASA Image and Video Library

    2009-09-21

    This mosaic, part of a larger mosaic of images captured by NASA Cassini Orbiter just hours before exact equinox at Saturn, shows that the spiral corrugation in the planet’s inner rings continues right up to the inner B ring.

  14. The Fermilab recycler ring

    SciTech Connect

    Martin Hu

    2001-07-24

    The Fermilab Recycler is a permanent magnet storage ring for the accumulation of antiprotons from the Antiproton Source, and the recovery and cooling of the antiprotons remaining at the end of a Tevatron store. It is an integral part of the Fermilab III luminosity upgrade. The following paper describes the design features, operational and commissioning status of the Recycler Ring.

  15. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  16. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  17. DC-Powered Jumping Ring

    NASA Astrophysics Data System (ADS)

    Jeffery, Rondo N.; Amiri, Farhang

    2016-02-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant differences from the AC case. In particular, the ring does not fly off the core but rises a short distance and then falls back. If the ring jumps high enough, the rising and the falling motion of the ring does not follow simple vertical motion of a projectile. This indicates that there are additional forces on the ring in each part of its motion. Four possible stages of the motion of the ring with DC are identified, which result from the ring current changing directions during the jump in response to a changing magnetic flux through the moving ring.

  18. Obscured by Rings

    NASA Image and Video Library

    2012-08-29

    Saturn rings obscure part of Titan colorful visage in this image from NASA Cassini spacecraft. The south polar vortex that first appeared in Titan atmosphere in 2012 is visible at the bottom of this view.

  19. (1) H NMR Spectra. Part 28: Proton chemical shifts and couplings in three-membered rings. A ring current model for cyclopropane and a novel dihedral angle dependence for (3) J(HH) couplings involving the epoxy proton.

    PubMed

    Abraham, Raymond J; Leonard, Paul; Tormena, Cláudio F

    2012-04-01

    The (1) H chemical shifts of selected three-membered ring compounds in CDCl(3) solvent were obtained. This allowed the determination of the substituent chemical shifts of the substituents in the three-membered rings and the long-range effect of these rings on the distant protons. The substituent chemical shifts of common substituents in the cyclopropane ring differ considerably from the same substituents in acyclic fragments and in cyclohexane and were modelled in terms of a three-bond (γ)-effect. For long-range protons (more than three bonds removed), the substituent effects of the cyclopropane ring were analysed in terms of the cyclopropane magnetic anisotropy and steric effect. The cyclopropane magnetic anisotropy (ring current) shift was modelled by (a) a single equivalent dipole perpendicular to and at the centre of the cyclopropane ring and (b) by three identical equivalent dipoles perpendicular to the ring placed at each carbon atom. Model (b) gave a more accurate description of the (1) H chemical shifts and was the selected model. After parameterization, the overall root mean square error for the dataset of 289 entries was 0.068 ppm. The anisotropic effects are significant for the cyclopropane protons (ca 1 ppm) but decrease rapidly with distance. The heterocyclic rings of oxirane, thiirane and aziridine do not possess a ring current. (3) J(HH) couplings of the epoxy ring proton with side-chain protons were obtained and shown to be dependent on both the H-C-C-H and H-C-C-O orientations. Both density functional theory calculations and a simple Karplus-type equation gave general agreement with the observed couplings (root mean square error 0.5 Hz over a 10-Hz range).

  20. Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2014-12-01

    The rings are changing before our eyes; structure varies on all timescales and unexpected things have been discovered. Many questions have been answered, but some answers remain elusive (see Cuzzi et al 2010 for a review). Here we highlight the major ring science progress over the mission to date, and describe new observations planned for Cassini's final three years. Ring Composition and particle sizes: The rings are nearly all water ice with no other ices - so why are they reddish? The C Ring and Cassini Division are "dirtier" than the more massive B and A Rings, as shown by near-IR and, recently, microwave observations. Particle sizes, from stellar and radio occultations, vary from place to place. Ring structure, micro and macro: numerous spiral density waves and ubiquitous "self-gravity wakes" reveal processes which fostered planet formation in the solar system and elsewhere. However, big puzzles remain regarding the main ring divisions, the C Ring plateau structures, and the B Ring irregular structure. Moonlets, inside and out, seen and unseen: Two gaps contain sizeable moonlets, but more gaps seem to contain none; even smaller embedded "propeller" objects wander, systematically or randomly, through the A ring. Rubble pile ringmoons just outside the rings may escaped from the rings, and the recently discovered "Peggy" may be trying this as we watch. Impact bombardment of the rings: Comet fragments set the rings to rippling on century-timescales, and boulders crash through hourly; meanwhile, the constant hail of infalling Kuiper belt material has a lower mass flux than previously thought. Origin and Age of the Rings: The ring mass and bombardment play key roles. The ring mass is well known everywhere but in the B Ring (where most of it is). New models suggest how tidal breakup of evolving moons may have formed massive ancient rings, of which the current ring is just a shadow. During its last three years, the Cassini tour profile will allow entirely new

  1. Rings in the solar system

    SciTech Connect

    Pollack, J.B.; Cuzzi, J.N.

    1981-11-01

    Saturn, Jupiter, and Uranus have rings with different structure and composition. The rings consist of tiny masses in independent orbits. Photographs and data obtained by the Voyager project have aided in the understanding of Saturn's rings. Spokes have been found in B ring and boards, knots, and twist in F ring. Particles on the order of a micrometer in size are believed to occur in F, B, and A rings. The dominant component is water ice. The rings of Uranus are narrow and separated by broad empty regions. The technique used to study them has been stellar occulation. Nothing is known of particle size. The dominant component is believed to be silicates rich in compounds that absorb sunlight. Jupiter's rings consist of 3 main parts: a bright ring, a diffuse disk, and a halo. Use of Pioneer 10 data and other techniques have indicated particle sizes on the order of several micrometers and some at least a centimeter in diameter. The architecture of the ring system results from the interplay of a number of forces. These include gravitational forces due to moons outside the rings and moonlets embedded in them, electromagnetic forces due to the planet's rotating magnetic field, and even the gentle forces exerted by the dilute gaseous medium in which the rings rotate. Each of these forces is discussed. Several alternative explanations of how the rings arose are considered. The primary difference in these hypotheses is the account of the relationship between the ring particles of today and the primordial ring material. (SC)

  2. Neptune's rings

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This 591-second exposure of the rings of Neptune were taken with the clear filter by the Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged. Also visible in this image is the inner faint ring and the faint band which extends smoothly from the ring roughly halfway between the two bright rings. Both of these newly discovered rings are broad and much fainter than the two narrow rings. The bright glare is due to over-exposure of the crescent on Neptune. Numerous bright stars are evident in the background. Both bright rings have material throughout their entire orbit, and are therefore continuous. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

  3. Ring World

    NASA Image and Video Library

    2007-03-01

    Our robotic emissary, flying high above Saturn, captured this view of an alien copper-colored ring world. The overexposed planet has deliberately been removed to show the unlit rings alone, seen from an elevation of 60 degrees

  4. Neptune Rings

    NASA Image and Video Library

    1999-10-29

    This 591-second exposure of the rings of Neptune were taken with the clear filter by NASA Voyager 2 wide-angle camera. The two main rings are clearly visible and appear complete over the region imaged.

  5. Ring Backdrop

    NASA Image and Video Library

    2011-01-03

    Saturn moon Enceladus brightly reflects sunlight before a backdrop of the planet rings and the rings shadows cast onto the planet. NASA Cassini spacecraft captured this snapshot during its flyby of the moon on Nov. 30, 2010.

  6. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  7. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  8. Jupiter Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest being

  9. Hydrogenation of the Exocyclic Olefinic Bond at C-16/C-17 Position of ent-Kaurane Diterpene Glycosides of Stevia rebaudiana Using Various Catalysts

    PubMed Central

    Chaturvedula, Venkata Sai Prakash; Prakash, Indra

    2013-01-01

    Catalytic hydrogenation of the exocyclic double bond present between C16 and C17 carbons of the four ent-kaurane diterpene glycosides namely rebaudioside A, rebaudioside B, rebaudioside C, and rebaudioside D isolated from Stevia rebaudiana has been carried out using Pt/C, Pd(OH)2, Rh/C, Raney Ni, PtO2, and 5% Pd/BaCO3 to their corresponding dihydro derivatives with 17α and 17β methyl group isomers. Reactions were performed using the above-mentioned catalysts with the solvents methanol, water, and ethanol/water (8:2) under various conditions. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data, including a comparison with reported spectral data. PMID:23896597

  10. Hydrogenation of the exocyclic olefinic bond at C-16/C-17 position of ent-kaurane diterpene glycosides of Stevia rebaudiana using various catalysts.

    PubMed

    Chaturvedula, Venkata Sai Prakash; Prakash, Indra

    2013-07-26

    Catalytic hydrogenation of the exocyclic double bond present between C16 and C17 carbons of the four ent-kaurane diterpene glycosides namely rebaudioside A, rebaudioside B, rebaudioside C, and rebaudioside D isolated from Stevia rebaudiana has been carried out using Pt/C, Pd(OH)2, Rh/C, Raney Ni, PtO2, and 5% Pd/BaCO3 to their corresponding dihydro derivatives with 17α and 17β methyl group isomers. Reactions were performed using the above-mentioned catalysts with the solvents methanol, water, and ethanol/water (8:2) under various conditions. Synthesis of reduced steviol glycosides was performed using straightforward chemistry and their structures were characterized on the basis of 1D and 2D NMR spectral data, including a comparison with reported spectral data.

  11. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of

  12. Apatitic connecting rings in moulds of Baculites sp. from the middle part of the Smoky Hill Member, Niobrara Chalk (Santonian), of western Kansas

    USGS Publications Warehouse

    Hasenmueller, W.A.; Hattin, D.E.

    1985-01-01

    Moulds of Baculites sp. are common in the Smoky Hill Member but only five known specimens contain connecting rings that have been preserved because of mineralisation by carbonate apatite. Analysis of four of these specimens suggests that the connecting rings were originally composed of organic material and were mineralised during early diagenesis. Thin sections and scanning electron microscopy demonstrate that the connecting rings had a two-layered structure consisting of a thick siphuncular wall and a thin pellicle. ?? 1985.

  13. Vortex rings

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Leonard, Anthony

    1992-01-01

    The vortex-ring problem in fluid mechanics is examined generally in terms of formation, the steady state, the duration of the rings, and vortex interactions. The formation is studied by examining the generation of laminar and turbulent vortex rings and their resulting structures with attention given to the three stages of laminar ring development. Inviscid dynamics is addressed to show how core dynamics affects overall ring motion, and laminar vortex structures are described in two dimensions. Viscous and inviscid structures are related in terms of 'leapfrogging', head-on collisions, and collisions with a no-slip wall. Linear instability theory is shown to successfully describe observational data, although late stages in the breakdown are not completely understood. This study of vortex rings has important implications for key aerodynamic issues including sound generation, transport and mixing, and vortex interactions.

  14. Translucent Rings

    NASA Image and Video Library

    2014-12-08

    Although solid-looking in many images, Saturn's rings are actually translucent. In this picture, we can glimpse the shadow of the rings on the planet through (and below) the A and C rings themselves, towards the lower right hand corner. For centuries people have studied Saturn's rings, but questions about the structure and composition of the rings lingered. It was only in 1857 when the physicist James Clerk Maxwell demonstrated that the rings must be composed of many small particles and not solid rings around the planet, and not until the 1970s that spectroscopic evidence definitively showed that the rings are composed mostly of water ice. This view looks toward the sunlit side of the rings from about 17 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on Aug. 12, 2014 in near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.3 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 24 degrees. Image scale is 85 miles (136 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18295

  15. Application of the Green's function method to some nonlinear problems of an electron storage ring: Part 1, The Green's function for the Fokker-Planck equation

    SciTech Connect

    Kheifets, S.

    1982-07-01

    For an electron storage ring the beam size evaluation including beam-beam interaction gives an example of such a problem. Another good example is finding the beam size for a nonlinear machine. The present work gives a way to solve some of these problems, at least in principle. The approach described here is an application of the well known Green's function method, which in this case is applied to the Fokker-Planck equation governing the distribution function in the phase space of particle motion. The new step made in this paper is to consider the particle motion in two degrees of freedom rather than in one dimension, a characteristic of all the previous work. This step seems to be necessary for an adequate description of the problem, at least for the class of problems which are considered below. This work consists of the formal solution of the Fokker-Planck equation in terms of its Green's function and describing the Green's function itself. The Green's function and the description of some of its properties can be found in the Appendices. I discuss the distribution function in the transverse phase space of a particle and it's Fokker-Planck equation for a simple case of a weak focusing machine. Part of this paper is devoted to describing the Green's function and solution of this equation. Then this technique is applied to a strong focusing machine and finally there is a discussion of applicability of this method, its limitations and relation to other methods. 13 refs.

  16. Reinforcement core facilitates O-ring installation

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Reinforcement core holds O-ring in place within a structure while adjacent parts are being assembled. The core in the O-ring adds circumferential rigidity to the O-ring material. This inner core does not appreciably affect the sectional elasticity or gland-sealing characteristics of the O-ring.

  17. The Enceladus Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled)

    This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background.

    The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view.

    Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring.

    Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione.

    An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus.

    One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane.

    Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally

  18. The Enceladus Ring

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] The Enceladus Ring (labeled)

    This excellent view of the faint E ring -- a ring feature now known to be created by Enceladus -- also shows two of Saturn's small moons that orbit within the ring, among a field of stars in the background.

    The E ring extends from three to eight Saturn radii -- about 180,000 kilometers (118,000 miles) to 482,000 kilometers (300,000 miles). Its full extent is not visible in this view.

    Calypso (22 kilometers, or 14 miles across) and Helene (32 kilometers, or 20 miles across) orbit within the E ring's expanse. Helene skirts the outer parts of the E ring, but here it is projected in front of a region deeper within the ring.

    Calypso and Helene are trojan satellites, or moons that orbit 60 degrees in front or behind a larger moon. Calypso is a Tethys trojan and Helene is a trojan of Dione.

    An interesting feature of note in this image is the double-banded appearance of the E-ring, which is created because the ring is somewhat fainter in the ringplane than it is 500-1,000 kilometers (300-600 miles) above and below the ringplane. This appearance implies that the particles in this part of the ring have nonzero inclinations (a similar affect is seen in Jupiter's gossamer ring). An object with a nonzero inclination does not orbit exactly at Saturn's ringplane. Instead, its orbit takes it above and below the ringplane. Scientists are not entirely sure why the particles should have such inclinations, but they are fairly certain that the reason involves Enceladus.

    One possible explanation is that all the E ring particles come from the plume of icy material that is shooting due south out of the moon's pole. This means all of the particles are created with a certain velocity out of the ringplane, and then they orbit above and below that plane.

    Another possible explanation is that Enceladus produces particles with a range of speeds, but the moon gravitationally

  19. Widening Rings

    NASA Image and Video Library

    2010-03-18

    Saturn rings and its moon Rhea are imaged before a crescent of the planet in this image captured by NASA Cassini spacecraft. The shadows of the rings continue to grow wider after their disappearing act during the planet August 2009 equinox.

  20. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

  1. Ring Slicer

    NASA Image and Video Library

    2015-07-06

    Saturn's moon Prometheus, seen here looking suspiciously blade-like, is captured near some of its sculpting in the F ring. Prometheus' (53 miles or 86 kilometers across) orbit sometimes takes it into the F ring. When it enters the ring, it leaves a gore where its gravitational influence clears out some of the smaller ring particles. Below Prometheus, the dark lanes interior to the F ring's bright core provide examples of previous ring-moon interactions. This view looks toward the unilluminated side of the rings from about 7 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on March 15, 2015. The view was obtained at a distance of approximately 286,000 miles (461,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 115 degrees. Image scale is 1.7 miles (2.8 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18324

  2. Planetary Rings

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.

    1994-01-01

    Just over two decades ago, Jim Pollack made a critical contribution to our understanding of planetary ring particle properties, and resolved a major apparent paradox between radar reflection and radio emission observations. At the time, particle properties were about all there were to study about planetary rings, and the fundamental questions were, why is Saturn the only planet with rings, how big are the particles, and what are they made of? Since then, we have received an avalanche of observations of planetary ring systems, both from spacecraft and from Earth. Meanwhile, we have seen steady progress in our understanding of the myriad ways in which gravity, fluid and statistical mechanics, and electromagnetism can combine to shape the distribution of the submicron-to-several-meter size particles which comprise ring systems into the complex webs of structure that we now know them to display. Insights gained from studies of these giant dynamical analogs have carried over into improved understanding of the formation of the planets themselves from particle disks, a subject very close to Jim's heart. The now-complete reconnaissance of the gas giant planets by spacecraft has revealed that ring systems are invariably found in association with families of regular satellites, and there is ark emerging perspective that they are not only physically but causally linked. There is also mounting evidence that many features or aspects of all planetary ring systems, if not the ring systems themselves, are considerably younger than the solar system

  3. Hot piston ring tests

    NASA Technical Reports Server (NTRS)

    Allen, David J.; Tomazic, William A.

    1987-01-01

    As part of the DOE/NASA Automotive Stirling Engine Project, tests were made at NASA Lewis Research Center to determine whether appendix gap losses could be reduced and Stirling engine performance increased by installing an additional piston ring near the top of each piston dome. An MTI-designed upgraded Mod I Automotive Stirling Engine was used. Unlike the conventional rings at the bottom of the piston, these hot rings operated in a high temperature environment (700 C). They were made of a high temperature alloy (Stellite 6B) and a high temperature solid lubricant coating (NASA Lewis-developed PS-200) was applied to the cylinder walls. Engine tests were run at 5, 10, and 15 MPa operating pressure over a range of operating speeds. Tests were run both with hot rings and without to provide a baseline for comparison. Minimum data to assess the potential of both the hot rings and high temperature low friction coating was obtained. Results indicated a slight increase in power and efficiency, an increase over and above the friction loss introduced by the hot rings. Seal leakage measurements showed a significant reduction. Wear on both rings and coating was low.

  4. Application of the Green's function method to some nonlinear problems of an electron storage ring: Part 2, Checking the method by a quadrupole perturbation

    SciTech Connect

    Kheifets, S.

    1982-10-01

    In the first part of this work I described a general approach to some storage ring problems. The basic concept and the main equations were developed there. The next natural step in this work should be an application of the developed technique to some particular nonlinear problem. Instead, I found it useful to apply the method to the case of a field gradient perturbation first. This happened to be plausible not only as a check of the method, but, more importantly, as a way to resolve several troublesome difficulties encountered in subsequent calculations. The present note does not contain any new results. Still, the work is felt to be necessary as a support for all the future applications of the method. I consider here the effect of a global gradient error in a weak-focusing machine and the effect of a local gradient error in a strong focusing machine. The distribution function of a particle bunch for a perturbed lattice in these cases can be written explicitly. The expansion of this distribution function as a series perturbation terms produces the first and the second order corrections to the unperturbed function. From them we calculate, then, corresponding second moments. A similar expansion of the distribution function is found by the Green's function method described of this work. The second moments are found independently with the help of this distribution function. The comparison of these two results is one way to check the method and the correctness of the calculations. This comparison is done for the first and second order perturbations. 4 refs., 2 tabs.

  5. Benzopyrans as selective estrogen receptor beta agonists (SERBAs). Part 3: synthesis of cyclopentanone and cyclohexanone intermediates for C-ring modification.

    PubMed

    Richardson, Timothy I; Dodge, Jeffrey A; Durst, Gregory L; Pfeifer, Lance A; Shah, Jikesh; Wang, Yong; Durbin, Jim D; Krishnan, Venkatesh; Norman, Bryan H

    2007-09-01

    Benzopyrans are selective estrogen receptor (ER) beta agonists (SERBAs), which bind the ER subtypes alpha and beta in opposite orientations. Here we describe the syntheses of cyclopentanone and cyclohexanone intermediates for SAR studies of the C-ring on the benzopyran scaffold. Modification of the C-ring disrupts binding to ERalpha, thus improving ERbeta selectivity up to 100-fold. X-ray cocrystal structures confirm previously observed binding modes.

  6. A ditopic O(4)S(2) macrocycle and its hard, soft, and hard/soft metal complexes exhibiting endo-, exo-, or endo/exocyclic coordination: synthesis, crystal structures, NMR titration, and physical properties.

    PubMed

    Ryu, Hyunsoo; Park, Ki-Min; Ikeda, Mari; Habata, Yoichi; Lee, Shim Sung

    2014-04-21

    A 20-membered O4S2 macrocycle (L(2)) was synthesized as a ditopic ligating system toward hard and soft metal ions simultaneously. Five complexes (3-7) of L(2) with different structures and coordination modes, including discrete to infinite forms, mono- to heteronuclear, and endo- to exo- and endo/exocoordination, were prepared and structurally characterized. First, the reaction of L(2) with Pb(ClO4)2·3H2O afforded a typical endocyclic mononuclear perchlorato complex [Pb(L(2))(ClO4)2] (3) in which one lead(II) is surrounded by the macrocycle adopting a "tight and bent" conformation. Meanwhile, the reaction with a softer metal salt AgNO3 resulted in the formation of the dinuclear bis(macrocycle) complex [Ag2(L(2))2(NO3)2] (4) in which two exocyclic silver(I) ions are doubly linked by two nitrate ions. The treatment of L(2) with CuI gave a mixture of the exocyclic monomer complex [Cu(L(2))I] (5) and the exocyclic dimer complex [(Cu2I2)(L(2))2] (6), which were separated manually because of their brick and rhomboid shapes of the crystals, respectively. Furthermore, the reaction of L(2) with a mixture of CuI and NaI afforded a photoluminescent heteronuclear complex [Na2(Cu6I8)(L(2))2(CH3CN)4]n (7) in the endo/exocyclic coordination mode. In this case, the endocyclic sodium(I) complex units are linked by the double-open cubanes-type cluster Cu6I8, yielding a two-dimensional network. The structural and binding properties of the complex of L(2) with silver(I) nitrate in solution were monitored by the NMR titration. Photophysical and thermal properties for complex 7 were also investigated and discussed.

  7. Ring King

    NASA Image and Video Library

    2014-08-18

    Saturn reigns supreme, encircled by its retinue of rings. Although all four giant planets have ring systems, Saturn's is by far the most massive and impressive. Scientists are trying to understand why by studying how the rings have formed and how they have evolved over time. Also seen in this image is Saturn's famous north polar vortex and hexagon. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on May 4, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was acquired at a distance of approximately 2 million miles (3 million kilometers) from Saturn. Image scale is 110 miles (180 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18278

  8. Ring-Bow

    NASA Image and Video Library

    2017-07-24

    Although the rings lack the many colors of the rainbow, they arc across the sky of Saturn. From equatorial locations on the planet, they'd appear very thin since they would be seen edge-on. Closer to the poles, the rings would appear much wider; in some locations (for parts of the Saturn's year), they would even block the sun for part of each day. This view looks toward the sunlit side of the rings from about 19 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on April 10, 2017. The view was obtained at a distance of approximately 680,000 miles (1.1 million kilometers) from Saturn and at a sun-Saturn-spacecraft, or phase, angle of 128 degrees. Image scale is 43 miles (69 kilometers) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21339

  9. Vascular rings.

    PubMed

    Backer, Carl L; Mongé, Michael C; Popescu, Andrada R; Eltayeb, Osama M; Rastatter, Jeffrey C; Rigsby, Cynthia K

    2016-06-01

    The term vascular ring refers to congenital vascular anomalies of the aortic arch system that compress the esophagus and trachea, causing symptoms related to those two structures. The most common vascular rings are double aortic arch and right aortic arch with left ligamentum. Pulmonary artery sling is rare and these patients need to be carefully evaluated for frequently associated tracheal stenosis. Another cause of tracheal compression occurring only in infants is the innominate artery compression syndrome. In the current era, the diagnosis of a vascular ring is best established by CT imaging that can accurately delineate the anatomy of the vascular ring and associated tracheal pathology. For patients with a right aortic arch there recently has been an increased recognition of a structure called a Kommerell diverticulum which may require resection and transfer of the left subclavian artery to the left carotid artery. A very rare vascular ring is the circumflex aorta that is now treated with the aortic uncrossing operation. Patients with vascular rings should all have an echocardiogram because of the incidence of associated congenital heart disease. We also recommend bronchoscopy to assess for additional tracheal pathology and provide an assessment of the degree of tracheomalacia and bronchomalacia. The outcomes of surgical intervention are excellent and most patients have complete resolution of symptoms over a period of time. Copyright © 2016 Elsevier Inc. All rights reserved.

  10. Nardo Ring, Italy

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Nardo Ring is a striking visual feature from space, and astronauts have photographed it several times. The Ring is a race car test track; it is 12.5 kilometers long and steeply banked to reduce the amount of active steering needed by drivers. The Nardo Ring lies in a remote area on the heel of Italy's 'boot,' 50 kilometers east of the naval port of Taranto. The Ring encompasses a number of active (green) and fallow (brown to dark brown) agricultural fields. In this zone of intensive agriculture, farmers gain access to their fields through the Ring via a series of underpasses. Winding features within the southern section of the Ring appear to be smaller, unused race tracks.

    The image covers an area of 18.8 x 16.4 km, was acquired on August 17. 2007, and is located at 49.3 degrees north latitude, 17.8 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  11. Saturn Ring

    NASA Image and Video Library

    2007-12-12

    Like Earth, Saturn has an invisible ring of energetic ions trapped in its magnetic field. This feature is known as a "ring current." This ring current has been imaged with a special camera on Cassini sensitive to energetic neutral atoms. This is a false color map of the intensity of the energetic neutral atoms emitted from the ring current through a processed called charged exchange. In this process a trapped energetic ion steals and electron from cold gas atoms and becomes neutral and escapes the magnetic field. The Cassini Magnetospheric Imaging Instrument's ion and neutral camera records the intensity of the escaping particles, which provides a map of the ring current. In this image, the colors represent the intensity of the neutral emission, which is a reflection of the trapped ions. This "ring" is much farther from Saturn (roughly five times farther) than Saturn's famous icy rings. Red in the image represents the higher intensity of the particles, while blue is less intense. Saturn's ring current had not been mapped before on a global scale, only "snippets" or areas were mapped previously but not in this detail. This instrument allows scientists to produce movies (see PIA10083) that show how this ring changes over time. These movies reveal a dynamic system, which is usually not as uniform as depicted in this image. The ring current is doughnut shaped but in some instances it appears as if someone took a bite out of it. This image was obtained on March 19, 2007, at a latitude of about 54.5 degrees and radial distance 1.5 million kilometres (920,000 miles). Saturn is at the center, and the dotted circles represent the orbits of the moon's Rhea and Titan. The Z axis points parallel to Saturn's spin axis, the X axis points roughly sunward in the sun-spin axis plane, and the Y axis completes the system, pointing roughly toward dusk. The ion and neutral camera's field of view is marked by the white line and accounts for the cut-off of the image on the left. The

  12. The Stereochemistry of trans-4-Hydroxynonenal-Derived Exocyclic 1,N2-2′-Deoxyguanosine Adducts Modulates Formation of Interstrand Cross-Links in the 5′-CpG-3′ Sequence†

    PubMed Central

    2008-01-01

    The trans-4-hydroxynonenal (HNE)-derived exocyclic 1,N2-dG adduct with (6S,8R,11S) stereochemistry forms interstrand N2-dG−N2-dG cross-links in the 5′-CpG-3′ DNA sequence context, but the corresponding adduct possessing (6R,8S,11R) stereochemistry does not. Both exist primarily as diastereomeric cyclic hemiacetals when placed into duplex DNA [Huang, H., Wang, H., Qi, N., Kozekova, A., Rizzo, C. J., and Stone, M. P. (2008) J. Am. Chem. Soc. 130, 10898−10906]. To explore the structural basis for this difference, the HNE-derived diastereomeric (6S,8R,11S) and (6R,8S,11R) cyclic hemiacetals were examined with respect to conformation when incorporated into 5′-d(GCTAGCXAGTCC)-3′·5′-d(GGACTCGCTAGC)-3′, containing the 5′-CpX-3′ sequence [X = (6S,8R,11S)- or (6R,8S,11R)-HNE−dG]. At neutral pH, both adducts exhibited minimal structural perturbations to the DNA duplex that were localized to the site of the adduction at X7·C18 and its neighboring base pair, A8·T17. Both the (6S,8R,11S) and (6R,8S,11R) cyclic hemiacetals were located within the minor groove of the duplex. However, the respective orientations of the two cyclic hemiacetals within the minor groove were dependent upon (6S) versus (6R) stereochemistry. The (6S,8R,11S) cyclic hemiacetal was oriented in the 5′-direction, while the (6R,8S,11R) cyclic hemiacetal was oriented in the 3′-direction. These cyclic hemiacetals effectively mask the reactive aldehydes necessary for initiation of interstrand cross-link formation. From the refined structures of the two cyclic hemiacetals, the conformations of the corresponding diastereomeric aldehydes were predicted, using molecular mechanics calculations. Potential energy minimizations of the duplexes containing the two diastereomeric aldehydes predicted that the (6S,8R,11S) aldehyde was oriented in the 5′-direction while the (6R,8S,11R) aldehyde was oriented in the 3′-direction. These stereochemical differences in orientation suggest a kinetic

  13. Single-staged vs. two-staged implant placement in vertically deficient alveolar ridges using bone ring technique - Part 2: implant osseointegration.

    PubMed

    Nakahara, Ken; Haga-Tsujimura, Maiko; Sawada, Kosaku; Kobayashi, Eizaburo; Schaller, Benoit; Saulacic, Nikola

    2017-07-01

    The aim of this study was to evaluate the osseointegration of implants placed in a single-staged compared to two-staged procedure using bone ring technique. In this study were used standardized, vertical alveolar bone defects in dogs. In the test group, dental implants (Straumann BL(®) , Basel, Switzerland) were inserted simultaneously with bone ring technique. As control group served implants inserted 6 months following grafting. Implants of both groups were left for an osseointegration period of 3 and 6 months. The peri-implant bone loss and bone-to-implant contact within the bone ring and native bone were analyzed morphometrically. An explorative statistical analysis was performed. The peri-implant bone level remained relatively stable within groups and between groups per given time period. Most of bone apposite on the implant surface in two groups was composed of newly formed bone. A nonparametric analysis of variance (ANOVA) revealed no significant advantage for two-staged implant placement for new and total bone, except for residual bone (P = .0084). Furthermore, two groups of implants performed similarly in bone ring and in native bone throughout the observation period. In terms of osseointegration, both techniques are likely equally efficient in the present defect model. The single-staged implant placement with cortical bone grafts warrants further documentation in clinical studies. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Cave Rings

    DTIC Science & Technology

    2010-10-13

    hypothesis, that cave rings are formed in the same manner as coffee rings[3], that is, due to the enhanced deposition at the edges of sessile drops ...Literature The ‘splash ring’ conjecture is described in [5]. It is claimed that 45◦ is the most probable angle for secondary drops to be ejected at, and that...ring’ is the deposit formed when a sessile drop of a solution containing dissolved particles, such as coffee or salt, dries. This was investigated by

  15. Propeller Churns the A Ring

    NASA Image and Video Library

    2010-07-08

    This image is part of a set of images obtained by NASA Cassini spacecraft showing a propeller-shaped structure created by a hidden, embedded moon moving through one of Saturn rings. An animation is available at the Photojournal.

  16. Stacked Corrugated Horn Rings

    NASA Technical Reports Server (NTRS)

    Sosnowski, John B.

    2010-01-01

    This Brief describes a method of machining and assembly when the depth of corrugations far exceeds the width and conventional machining is not practical. The horn is divided into easily machined, individual rings with shoulders to control the depth. In this specific instance, each of the corrugations is identical in profile, and only differs in diameter and outer profile. The horn is segmented into rings that are cut with an interference fit (zero clearance with all machining errors biased toward contact). The interference faces can be cut with a reverse taper to increase the holding strength of the joint. The taper is a compromise between the interference fit and the clearance of the two faces during assembly. Each internal ring is dipped in liquid nitrogen, then nested in the previous, larger ring. The ring is rotated in the nest until the temperature of the two parts equalizes and the pieces lock together. The resulting assay is stable, strong, and has an internal finish that cannot be achieved through other methods.

  17. Two F Ring Views

    NASA Technical Reports Server (NTRS)

    2005-01-01

    These views, taken two hours apart, demonstrate the dramatic variability in the structure of Saturn's intriguing F ring.

    In the image at the left, ringlets in the F ring and Encke Gap display distinctive kinks, and there is a bright patch of material on the F ring's inner edge. Saturn's moon Janus (181 kilometers, or 113 miles across) is shown here, partly illuminated by reflected light from the planet.

    At the right, Prometheus (102 kilometers, or 63 miles across) orbits ahead of the radial striations in the F ring, called 'drapes' by scientists. The drapes appear to be caused by successive passes of Prometheus as it reaches the greatest distance (apoapse) in its orbit of Saturn. Also in this image, the outermost ringlet visible in the Encke Gap displays distinctive bright patches.

    These views were obtained from about three degrees below the ring plane.

    The images were taken in visible light with the Cassini spacecraft narrow-angle camera on June 29, 2005, when Cassini was about 1.5 million kilometers (900,000 miles) from Saturn. The image scale is about 9 kilometers (6 miles) per pixel.

  18. Pleuromutilin derivatives having a purine ring. Part 2: influence of the central spacer on the antibacterial activity against Gram-positive pathogens.

    PubMed

    Hirokawa, Yoshimi; Kinoshita, Hironori; Tanaka, Tomoyuki; Nakamura, Takanori; Fujimoto, Koichi; Kashimoto, Shigeki; Kojima, Tsuyoshi; Kato, Shiro

    2009-01-01

    Structural modification of the 4-piperidinethio moiety, as a spacer of the first pleuromutilin analogues 2A and 2B having a purine ring, led to discovery of the novel pleuromutilin derivatives 14B and 17B. These compounds with good solubility in water showed promising in vitro antibacterial activity against various Gram-positive bacteria including MRSA, PRSP, and VRE and have potent in vivo efficacy.

  19. Statistical ring current of Saturn

    NASA Astrophysics Data System (ADS)

    Carbary, J. F.; Achilleos, N.; Arridge, C. S.

    2012-06-01

    The statistical ring current of Saturn has been determined from the curl of the median magnetic field derived from over 5 years of observations of the Cassini magnetometer. The main issue addressed here is the calculation of the statistical ring current of Saturn by directly computing, for the first time, the symmetrical part of the ring current J from the Maxwell equation ∇ × B = μ0J from assembling the perturbation magnetic field B from 2004 through 2010. This study validates previous studies, based on fewer data and not using ∇ × B, and shows that the ring current flows eastward (in the +ϕ or corotation direction) and extends from ˜3 RS to at least ˜20 RS (1 RS = 60,268 km), which is the vicinity of the dayside magnetopause; that the ring current has a peak strength of ˜75 pA/m2 at ˜9.5 RS; and that the ring current has a half-width of ˜1.5 RS. Two outcomes of this study are that the ring current bends northward, as suggested by the “bowl” model of Saturn's plasma sheet, and that the total ring current is 9.2 ± 1.0 MA. In the context of future endeavors, the statistical ring current presented here can be used for calculations of the magnetic field of Saturn for particle drifts, field line mapping, and J × B force.

  20. Molecular basis for nucleotide-binding specificity: role of the exocyclic amino group "N2" in recognition by a guanylyl-ribonuclease.

    PubMed

    Schrift, Greta L; Waldron, Travis T; Timmons, Mitchell A; Ramaswamy, S; Kearney, William R; Murphy, Kenneth P

    2006-01-06

    Proteins interact with nucleotides to perform a multitude of functions within cells. These interactions are highly specific; however, the molecular basis for this specificity is not well understood. To identify factors critical for protein-guanine nucleotide recognition the binding of two closely related ligands, guanosine 3'-monophosphate (3'GMP) and inosine 3'-monophosphate (3'IMP), to Ribonuclease Sa (RNase Sa), a small, guanylyl-endoribonuclease from Streptomyces aureofaciens, was compared using isothermal titration calorimetry, NMR, X-ray crystallography and molecular dynamics simulations. This comparison has allowed for the determination of the contribution of the exocyclic amino group "N2" of the guanine base to nucleotide binding specificity. Calorimetric measurements indicate that RNase Sa has a higher affinity for 3'GMP (K=(1.5+/-0.2)x10(5)) over 3'IMP (K=(3.1+/-0.2)x10(4)) emphasizing the importance of N2 as a key determinant of RNase Sa guanine binding specificity. This result was unexpected as the published structural data for RNase Sa in complex with 3'GMP showed only a potential long-range interaction (>3.3A) between N2 and the side-chain of Glu41 of RNase Sa. The observed difference in affinity is largely due to a reduction in the favorable enthalpy change by 10 kJ/mol for 3'IMP binding as compared to 3'GMP that is accompanied by a significant difference in the heat capacity changes observed for binding the two ligands. To aid interpretation of the calorimetric data, the first crystal structure of a small, guanylyl ribonuclease bound to 3'IMP was determined to 2.0 A resolution. This structure has revealed small yet unexpected changes in the ligand conformation and differences in the conformations of the side-chains contacting the sugar and phosphate moieties as compared to the 3'GMP complex. The structural data suggest the less favorable enthalpy change is due to an overall lengthening of the contacts between RNase Sa and 3'IMP as compared to 3'GMP

  1. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2013-12-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~<500m in size) have been indirectly identified in Saturn's A ring through their propeller signature in the images. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring. In this paper we present evidence for the existence of propellers in Saturn's B ring by combining data from Cassini Ultraviolet Imaging Spectrograph (UVIS) and Imaging Science Subsystem (ISS) experiments. We show evidence that B ring seems to harbor two distinct populations of propellers: "big" propellers covering tens of degrees in azimuth situated in the densest part of B ring, and "small" propellers in less dense inner B ring that are similar in size and shape to known A ring propellers. The population of "big" propellers is exemplified with a single object which is observed for 5 years of Cassini data. The object is seen as a very elongated bright stripe (40 degrees wide) in unlit Cassini images, and dark stripe in lit geometries. In total we report observing the feature in images at 18 different epochs between 2005 and 2010. In UVIS occultations we observe this feature as an optical depth depletion in 14 out of 93 occultation cuts at corrotating longitudes compatible with imaging data. Combining the available Cassini data we infer that the object is a partial gap located at r=112,921km embedded in the high optical depth region of the B

  2. Synthesis and biological evaluation of novel N-phenyl ureidobenzenesulfonate derivatives as potential anticancer agents. Part 2. Modulation of the ring B.

    PubMed

    Gagné-Boulet, Mathieu; Moussa, Hanane; Lacroix, Jacques; Côté, Marie-France; Masson, Jean-Yves; Fortin, Sébastien

    2015-10-20

    DNA double strand-breaks (DSBs) are the most deleterious lesions that can affect the genome of living beings and are lethal if not quickly and properly repaired. Recently, we discovered a new family of anticancer agents designated as N-phenyl ureidobenzenesulfonates (PUB-SOs) that are blocking the cells cycle progression in S-phase and inducing DNA DSBs. Previously, we have studied the effect of several modifications on the molecular scaffold of PUB-SOs on their cytocidal properties. However, the effect of the nature and the position of substituents on the aromatic ring B is still poorly studied. In this study, we report the preparation and the biological evaluation of 45 new PUB-SO derivatives substituted by alkyl, alkoxy, halogen and nitro groups at different positions on the aromatic ring B. All PUB-SOs were active in the submicromolar to low micromolar range (0.24-20 μM). The cell cycle progression analysis showed that PUB-SOs substituted at position 2 by alkyl, halogen or nitro groups or substituted at position 4 by a hydroxyl group arrest the cell cycle progression in S-phase. Interestingly, all others PUB-SOs substituted at positions 3 and 4 arrested the cell cycle in G2/M-phase. PUB-SOs arresting the cell cycle progression in S-phase also induced the phosphorylation of H2AX (γH2AX) which is indicating the generation of DNA DSBs. We evidenced that few modifications on the ring B of PUB-SOs scaffold lead to cytocidal derivatives arresting the cell cycle in S-phase and inducing γH2AX and DSBs. In addition, this study shows that these new anticancer agents are promising and could be used as alternative to circumvent some of the biopharmaceutical complications that might be encountered during the development of PUB-SOs. Copyright © 2015 Elsevier Masson SAS. All rights reserved.

  3. Advances in microbicide vaginal rings.

    PubMed

    Malcolm, R Karl; Edwards, Karen-Leigh; Kiser, Patrick; Romano, Joseph; Smith, Thomas J

    2010-12-01

    Vaginal ring devices capable of providing sustained/controlled release of incorporated actives are already marketed for steroidal contraception and estrogen replacement therapy. In recent years, there has been considerable interest in developing similar ring devices for the administration of microbicidal compounds to prevent vaginal HIV transmission. Intended to be worn continuously, such coitally independent microbicide rings are being developed to maintain effective vaginal microbicide concentrations over many weeks or months, thereby overcoming issues around timing of product application, user compliance and acceptability associated with more conventional semi-solid formulations. In this article, an overview of vaginal ring technologies is presented, followed by a review of recent advances and issues pertaining to their application for the delivery of HIV microbicides. This article forms part of a special supplement on presentations covering intravaginal rings, based on the symposium "Trends in Microbicide Formulations", held on 25 and 26 January 2010, Arlington, VA. Copyright © 2010 Elsevier B.V. All rights reserved.

  4. Formation of lunar basin rings

    USGS Publications Warehouse

    Hodges, C.A.; Wilhelms, D.E.

    1978-01-01

    The origin of the multiple concentric rings that characterize lunar impact basins, and the probable depth and diameter of the transient crater have been widely debated. As an alternative to prevailing "megaterrace" hypotheses, we propose that the outer scarps or mountain rings that delineate the topographic rims of basins-the Cordilleran at Orientale, the Apennine at Imbrium, and the Altai at Nectaris-define the transient cavities, enlarged relatively little by slumping, and thus are analogous to the rim crests of craters like Copernicus; inner rings are uplifted rims of craters nested within the transient cavity. The magnitude of slumping that occurs on all scarps is insufficient to produce major inner rings from the outer. These conclusions are based largely on the observed gradational sequence in lunar central uplifts:. from simple peaks through somewhat annular clusters of peaks, peak and ring combinations and double ring basins, culminating in multiring structures that may also include peaks. In contrast, belts of slump terraces are not gradational with inner rings. Terrestrial analogs suggest two possible mechanisms for producing rings. In some cases, peaks may expand into rings as material is ejected from their cores, as apparently occurred at Gosses Bluff, Australia. A second process, differential excavation of lithologically diverse layers, has produced nested experimental craters and is, we suspect, instrumental in the formation of terrestrial ringed impact craters. Peak expansion could produce double-ring structures in homogeneous materials, but differential excavation is probably required to produce multiring and peak-in-ring configurations in large lunar impact structures. Our interpretation of the representative lunar multiring basin Orientale is consistent with formation of three rings in three layers detected seismically in part of the Moon-the Cordillera (basin-bounding) ring in the upper crust, the composite Montes Rook ring in the underlying

  5. Ringing wormholes

    SciTech Connect

    Konoplya, R.A.; Molina, C.

    2005-06-15

    We investigate the response of traversable wormholes to external perturbations through finding their characteristic frequencies and time-domain profiles. The considered solution describes traversable wormholes between the branes in the two brane Randall-Sundrum model and was previously found within Einstein gravity with a conformally coupled scalar field. The evolution of perturbations of a wormhole is similar to that of a black hole and represents damped oscillations (ringing) at intermediately late times, which are suppressed by power-law tails (proportional to t{sup -2} for monopole perturbations) at asymptotically late times.

  6. A new approach to construct a fused 2-ylidene chromene ring: highly regioselective synthesis of novel chromeno quinoxalines.

    PubMed

    Kumar, K Shiva; Rambabu, D; Prasad, Bagineni; Mujahid, Mohammad; Krishna, G Rama; Rao, M V Basaveswara; Reddy, C Malla; Vanaja, G R; Kalle, Arunasree M; Pal, Manojit

    2012-06-28

    Regioselective construction of a fused 2-ylidene chromene ring was achieved for the first time by using AlCl(3)-induced C-C bond formation followed by Pd/C-Cu mediate coupling-cyclization strategy. A number of chromeno[4,3-b]quinoxaline derivatives were prepared by using this strategy. Single crystal X-ray diffraction study of a representative compound e.g. 6-(2,2-dimethylpropylidene)-4-methyl-6H-chromeno[4,3-b]quinoxalin-3-ol confirmed the presence of an exocyclic C-C double bond with Z-geometry. The crystal structure analysis and hydrogen bonding patterns of the same compound along with its structure elaboration via propargylation followed by Sonogashira coupling of the resulting terminal alkyne is presented. A probable mechanism for the formation of 2-ylidene chromene ring is discussed. Some of the compounds synthesized showed anticancer properties when tested in vitro.

  7. The Saturn Ring Observer: In situ studies of planetary rings

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.; Tiscareno, M. S.; Spilker, L. J.

    2010-12-01

    As part of the Planetary Science Decadal Survey recently undertaken by the NRC's Space Studies Board for the National Academy of Sciences, studies were commissioned for a number of potential missions to outer planet targets. One of these studies examined the technological feasibility of a mission to carry out in situ studies of Saturn's rings, from a spacecraft placed in a circular orbit above the ring plane: the Saturn Ring Observer. The technical findings and background are discussed in a companion poster by T. R. Spilker et al. Here we outline the science goals of such a mission. Most of the fundamental interactions in planetary rings occur on spatial scales that are unresolved by flyby or orbiter spacecraft. Typical particle sizes in the rings of Saturn are in the 1 cm - 10 m range, and average interparticle spacings are a few meters. Indirect evidence indicates that the vertical thickness of the rings is as little as 5 - 10 m, which implies a velocity dispersion of only a few mm/sec. Theories of ring structure and evolution depend on the unknown characteristics of interparticle collisions and on the size distribution of the ring particles. The SRO could provide direct measurements of both the coefficient of restitution -- by monitoring individual collisions -- and the particles’ velocity dispersion. High-resolution observations of individual ring particles should also permit estimates of their spin states. Numerical simulations of Saturn’s rings incorporating both collisions and self-gravity predict that the ring particles are not uniformly distributed, but are instead clustered into elongated structures referred to as “self-gravity wakes”, which are continually created and destroyed on an orbital timescale. Theory indicates that the average separation between wakes in the A ring is of order 30-100 m. Direct imaging of self-gravity wakes, including their formation and subsequent dissolution, would provide critical validation of these models. Other

  8. Kinetics of ring formation

    NASA Astrophysics Data System (ADS)

    Ben-Naim, E.; Krapivsky, P. L.

    2011-06-01

    We study reversible polymerization of rings. In this stochastic process, two monomers bond and, as a consequence, two disjoint rings may merge into a compound ring or a single ring may split into two fragment rings. This aggregation-fragmentation process exhibits a percolation transition with a finite-ring phase in which all rings have microscopic length and a giant-ring phase where macroscopic rings account for a finite fraction of the entire mass. Interestingly, while the total mass of the giant rings is a deterministic quantity, their total number and their sizes are stochastic quantities. The size distribution of the macroscopic rings is universal, although the span of this distribution increases with time. Moreover, the average number of giant rings scales logarithmically with system size. We introduce a card-shuffling algorithm for efficient simulation of the ring formation process and we present numerical verification of the theoretical predictions.

  9. δ(13)C and Water Use Efficiency in the Glucose of Annual Pine Tree Rings as Ecological Indicators of the Forests in the Most Industrialized Part of Poland.

    PubMed

    Sensuła, Barbara M

    In this study, stable carbon isotope ratios in the glucose samples were extracted from annual pine tree rings as bio-indicators of contemporary environmental changes in heavily urbanized areas. The sampling sites were located in close proximity to point source pollution emitters, such as a heat and power plant "Łaziska" and steelworks "Huta Katowice" in Silesia (Poland). The analysed samples covered the time span from 1975 to 2012 AD, the time period of the development of industrialization and the modernization in the industrial sector in Poland, similarly as in Eastern Europe. This modernization was connected with EU legislation and the implementation of restrictive governmental regulations on emissions. The carbon isotope discrimination has been proposed as a method for evaluating water use efficiency. The measurements of carbon isotopes were carried out using the continuous flow isotope ratio mass spectrometer coupled to the elemental analyser. The δ(13)C values were calibrated relative to the C-3 and C-5 international standards. Diffuse air pollution caused the variation in δ(13)C and iWUE (the ratio between CO2 assimilation and stomatal conductance) dependency on the type of emitter and some local effects of other human activities. In this study, the first results of water use efficiency in glucose are presented. In the period of time from 1975 to 2012, the water use efficiency values increased from 98 to 122 μmol/mol.

  10. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  11. Ring Bubbles of Dolphins

    NASA Technical Reports Server (NTRS)

    Shariff, Karim; Marten, Ken; Psarakos, Suchi; White, Don J.; Merriam, Marshal (Technical Monitor)

    1996-01-01

    The article discusses how dolphins create and play with three types of air-filled vortices. The underlying physics is discussed. Photographs and sketches illustrating the dolphin's actions and physics are presented. The dolphins engage in this behavior on their own initiative without food reward. These behaviors are done repeatedly and with singleminded effort. The first type is the ejection of bubbles which, after some practice on the part of the dolphin, turn into toroidal vortex ring bubbles by the mechanism of baroclinic torque. These bubbles grow in radius and become thinner as they rise vertically to the surface. One dolphin would blow two in succession and guide them to fuse into one. Physicists call this a vortex reconnection. In the second type, the dolphins first create an invisible vortex ring in the water by swimming on their side and waving their tail fin (also called flukes) vigorously. This vortex ring travels horizontally in the water. The dolphin then turns around, finds the vortex and injects a stream of air into it from its blowhole. The air "fills-out" the core of the vortex ring. Often, the dolphin would knock-off a smaller ring bubble from the larger ring (this also involves vortex reconnection) and steer the smaller ring around the tank. One other dolphin employed a few other techniques for planting air into the fluke vortex. One technique included standing vertically in the water with tail-up, head-down and tail piercing the free surface. As the fluke is waved to create the vortex ring, air is entrained from above the surface. Another technique was gulping air in the mouth, diving down, releasing air bubbles from the mouth and curling them into a ring when they rose to the level of the fluke. In the third type, demonstrated by only one dolphin, the longitudinal vortex created by the dorsal fin on the back is used to produce 10-15 foot long helical bubbles. In one technique she swims in a curved path. This creates a dorsal fin vortex since

  12. The Search for Ringed Exoplanets

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-04-01

    checks to eliminate false positives, the authors are left with one candidate: KIC 10403228.Rings or Not?Schematics of the two best-fitting ringed-exoplanet models for KIC 10403228, and the possible parameters of the system. The planet crosses the disk of the star from left to right with a grazing transit. [Adapted from Aizawa et al. 2017]Next, the authors apply a wide range of ringed-exoplanet models to KIC 10403228s light curve. They find two different scenarios that fit the data well: one in which the ring is significantly tilted with respect to the orbital plane, and another in which its only slightly tilted.The authors conclude by testing a variety of other scenarios that could explain the anomalies in the light curve instead. They find that two other scenarios are plausible: 1) the star is in an eclipsing binary system, with the second star surrounded by a circumstellar disk, and 2) the star is part of a hierarchical triple, and the transits are caused by a binary star system as it orbits KIC 10403228.Though Aizawa and collaborators arent able to rule either of these other two scenarios out, they suggest that follow-up spectroscopy or high-resolution imaging may help distinguish between the different scenarios. In the meantime, their methodology for systematically searching for ringed exoplanets has proven worthwhile, and they plan to extend it now to a larger data set. Perhaps well soon find other Saturn-like planets in our galaxy!CitationMasataka Aizawa () et al 2017 AJ 153 193. doi:10.3847/1538-3881/aa6336

  13. The ring of the narcissist.

    PubMed

    Shengold, L

    1995-12-01

    The author has not attempted a complete exposition of the meaning of rings--which can refer to and symbolise many aspects of relationships with other human beings from 'transitional objects' of early development (Winnicott) to all sorts of bonds of loyalty, friendship, and love in the life of the child and the adult. He stresses the meanings of the ring from the point of view of early narcissistic development--the 'body ego' time of early development in which symbolism (in Freud's sense) develops. The clinical and literary examples therefore illustrate the use of rings as magical narcissistic symbols--part subject and part object--derived developmentally from the body ego and ultimately from the body sphincters. Endowed with these regressive primitive meanings, rings are felt to have magical powers that can either preserve or destroy, and that can control emotions in the self and in others. In the course of ordinary or pathological narcissistic regressions, rings (consciously associated with many positive feelings and achievements) also partake, in so far as they are 'Freudian' symbols, of qualities associated with developmentally early defensive mechanisms and modes of psychic functioning (projection, introjection; idealisation, devaluation). In the cases cited, rings seemed specifically associated with (and to symbolise) sphincteric (largely anal) narcissistic defensiveness--the mind functioning as an emotional sphincteric counterpart primarily deadening and distancing affect but intermittently letting through primitive rage and primal polymorphous perverse sexual impulses.

  14. Ringing phenomenon of the fiber ring resonator.

    PubMed

    Ying, Diqing; Ma, Huilian; Jin, Zhonghe

    2007-08-01

    A resonator fiber-optic gyro (R-FOG) is a high-accuracy inertial rotation sensor based on the Sagnac effect. A fiber ring resonator is the core sensing element in the R-FOG. When the frequency of the fiber ring resonator input laser is swept linearly with time, ringing of the output resonance curve is observed. The output field of the fiber ring resonator is derived from the superposition of the light transmitted through the directional coupler directly and the multiple light components circulated in the fiber ring resonator when the frequency of the laser is swept. The amplitude and phase of the output field are analyzed, and it is found that the difference in time for different light components in the fiber ring resonator to reach a point of destructive interference causes the ringing phenomenon. Finally the ringing phenomenon is observed in experiments, and the experimental results agree with the theoretical analysis well.

  15. The Ring Sculptor

    NASA Image and Video Library

    2006-09-08

    Prometheus zooms across the Cassini spacecraft field of view, attended by faint streamers and deep gores in the F ring. This movie sequence of five images shows the F ring shepherd moon shaping the ring inner edge

  16. Beyond Bright Rings

    NASA Image and Video Library

    2009-12-30

    The tiny moon Pandora appears beyond the bright disk of Saturn rings in this image taken by NASA Cassini spacecraft. Pandora orbits outside the F ring and, in this image, is farther from Cassini than the rings are.

  17. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  18. Saturn's Spectacular Ring System

    NASA Technical Reports Server (NTRS)

    Lissauer, Jack J.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Saturn's beautiful rings have fascinated astronomers since they were first observed by Galileo in 1610. The main rings consist of solid particles mostly in the 1 cm - 10 m range, composed primarily of water ice. The ring disk is exceptionally thin - the typical local thickness of the bright rings is tens of meters, whereas the diameter of the main rings is 250,000 km! The main rings exhibit substantial radial variations "ringlets", many of which are actively maintained via gravitational perturbations from Saturn's moons. Exterior to the main rings lie tenuous dust rings, which have little mass but occupy a very large volume of space. This seminar will emphasize the physics of ring-moon interactions, recent advances in our understanding of various aspects of the rings obtained from observations taken during 1995 when the rings appeared edge-on to the Earth and then to the Sun, and observations in subsequent years from HST.

  19. Analysis of Ring Wake Simulations

    NASA Astrophysics Data System (ADS)

    Lewis, M. C.; Stewart, G. R.

    1999-09-01

    indent=20pt Collisional N-body simulations at the edge of a perturbed planetary ring are used to model the edges of the Encke gap in Saturn's rings. A small satellite, Pan, orbits inside the Encke gap and excites forced eccentricities and density wakes on both edges of the gap. The simulations use a local cell method to model a narrow ring using particles of the appropriate size for the A-ring at the proper optical depth. In the simulations we see evidence for shear reversal at the wake peaks. Our results imply that the most significant factor in the damping of the wakes is the reduction of the forced eccentricity and not randomization of the phase angles of the particles. The reduction of the forced eccentricity occurs in an orderly fashion with steep drops at each successive wake maximum following the highest density wake peak. indent=20pt At the inner edge (that nearer the perturber) we see phase shifts visible as bending of the line wake maxima. Because the simulations are actually of narrow rings, we also see a number of interesting phenomena at the outer edge. A strong boundary layer forms at that edge, which becomes partially detached from the rest of the ring. The wake patterns persist much further downstream in this boundary layer than they do in the rest of the ring. We also observe that in the less dense region between the main section of the ring and the boundary layer the magnitude of the forced eccentricities reverse their behavior in the main part and increase at each wake maxima. indent=20pt At the talk we will compare our results to the various analytic theories of Borderies, Goldreich, and Tremaine.

  20. Uranus Tenth Ring

    NASA Image and Video Library

    1996-01-29

    On Jan. 23, 1986, NASA Voyager 2 discovered a tenth ring orbiting Uranus. The tenth ring is about midway between the bright, outermost epsilon ring and the next ring down, called delta. http://photojournal.jpl.nasa.gov/catalog/PIA00035

  1. Stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1983-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  2. Birth Control Ring

    MedlinePlus

    ... Loss Surgery? A Week of Healthy Breakfasts Shyness Birth Control Ring KidsHealth > For Teens > Birth Control Ring Print A A A What's in this ... español Anillo vaginal anticonceptivo What Is It? The birth control ring is a soft, flexible, doughnut-shaped ring ...

  3. Saturn's E Ring in Ultraviolet Light

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Visible from Earth only at times of ring plane crossing, Saturn's tenuous E Ring was discovered during the 1966 crossings and imaged again in 1980. From these observations, its color is known to be distinctively blue. The E Ring was captured in ultraviolet light for the first time in this image taken with HST's Wide Field and Planetary Camera on 9 August 1995. Five individual images taken with a broadband 3000 A filter were combined, amounting to a total exposure time of 2200 sec. Shorter exposure images were also obtained with blue, red and infrared filters in order to characterize the ring's color. The peak brightness of the E Ring occurs at 3.9 Saturn radii (235,000 km), coinciding with the orbit of Enceladus. In the HST images it can be traced out to a maximum distance of approximately 8 Rs (480,000 km). The vertical thickness of the ring, on the other hand, is smallest at Enceladus' orbit, with the ring puffing up noticeably at larger distances to 15,000 km or more thick. Also visible in this image, between the E Ring and the overexposed outermost part of the main rings near the lower edge of the frame, is the tenuous, thin, 6000 km-wide G Ring at 2.8 Rs (170,000 km). This is among the first earth-based observations of the G Ring, which was discovered by the Pioneer 11 spacecraft in 1979. Noticeably thinner than the E Ring and more neutral in color, the G Ring is thought to be composed of larger, macroscopic particles, and to pose a significant hazard to spacecraft. The faint diagonal band in the lower right part of the image is due to diffracted light from the heavily-overexposed planet. Credit: Phil Nicholson (Cornell University), Mark Showalter (NASA-Ames/Stanford) and NASA

  4. New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

    SciTech Connect

    de Pater, I; Hammel, H B; Gibbard, S G; Showalter, M R

    2006-02-02

    We compare near-infrared observations of the recently discovered outer rings of Uranus with HST results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced via impacts into the embedded moon Mab, which apparently orbits at a location where non-gravitational perturbations favor the survival and spreading of sub-micron sized dust. R/2003 U 2 more closely resembles Saturn's G ring.

  5. Joining mechanism with stem tension and interlocked compression ring

    DOEpatents

    James, Allister W.; Morrison, Jay A.

    2012-09-04

    A stem (34) extends from a second part (30) through a hole (28) in a first part (22). A groove (38) around the stem provides a non-threaded contact surface (42) for a ring element (44) around the stem. The ring element exerts an inward force against the non-threaded contact surface at an angle that creates axial tension (T) in the stem, pulling the second part against the first part. The ring element is formed of a material that shrinks relative to the stem by sintering. The ring element may include a split collet (44C) that fits partly into the groove, and a compression ring (44E) around the collet. The non-threaded contact surface and a mating distal surface (48) of the ring element may have conic geometries (64). After shrinkage, the ring element is locked onto the stem.

  6. [Advances in the development of new antitubercular agents from orthocondensed heterocyclic compounds. Part 3. Substances containing several types of heteroatoms in the six-membered ring].

    PubMed

    Waisser, K; Bures, O; Holý, P

    2001-11-01

    Tuberculosis and other mycobacterial diseases are considered to be one of the most important problems of contemporary health service. Since 1985 and particularly in the 1990s and at present the search for new structures of antimycobacterial agents have ranked among the foremost areas of chemotherapeutic research. The present review paper is already the 18th communication in a group of review papers about substances with antituberculotic effects, and the third, final, communication devoted in this series about the development of new antimycobacterial agents to ortho-condensed heterocyclic compounds in recent 15 years. The classification of ortho-condensed compounds is based on six-membered heterocyclic substructural fragments and the present study deals with the substructural fragments containing a greater number of different heteroatoms. The literature search is based on the journal Chemical Abstracts, Current Awareness in Biomedicine, part Mycobacteria, and original papers. Current Awareness in Biomedicine is, however, a very imperfect literature search source, recording only a fraction of communications. Review papers about five-membered heterocyclic antituberculotic ortho-condensed compounds was published in the present journal in 1999.

  7. Accurate localization of organ representation areas of the tongue, using the Bi-Digital O-Ring Test: its clinical application, and re-evaluation of classical Oriental tongue diagnosis--Part I.

    PubMed

    Omura, Y

    1991-01-01

    In spite of the importance of tongue diagnosis in Oriental Medicine, a very rough assignment of only a limited number of the major internal organs is known, and some of the assignments are not exactly the same, depending upon various schools of thought. In 1980, the author first developed a simple, quick, non-invasive, accurate method of localizing representation areas of internal organs, using the Bi-Digital O-Ring Test Molecular Identification Method based on the resonance phenomena between 2 identical substances or tissues, with a microscope slide of a specific internal organ as a reference control substance. The method was applied to the organ representation areas in the ears, hands, feet, cerebral cortex, and tongue. In this article for the first time detailed organ representation areas of the human tongue are being presented in comparison with currently known organ representation areas on the tongue. For convenience, the tongue can be divided into 3 parts: the anterior, the middle, and the posterior. On each side of the anterior part (1st part, area around the tip) of the tongue, the internal organs in the chest cavity are represented; from the mid-line to each side of the tip of the tongue, the oesophagus, thymus gland, lung (and trachea & bronchi), heart, and breast (over heart area) are represented. The middle (2nd) part of the tongue represents the digestive system, and the 3rd part represents the genito-urinary system. The 2nd part of the tongue represents the rectum, colon, cecum, appendix, small intestine, stomach, pancreas, liver, and gall bladder. The 2nd and 3rd parts of the tongue represent all the internal organs in the abdominal cavities and the genito-urinary area. The remaining one-third of the tongue, near the pharynx, is all related to the genito-urinary system with the exception of the spleen, which is located between the kidney and the adrenal gland representation areas. Within the triangular area formed by the sulcus terminalis, the anus

  8. Present and future of scientific bird ringing

    USGS Publications Warehouse

    Spina, F.; Tautin, J.; Adams, N.J.; Slotow, R.H.

    1998-01-01

    In 1999 scientific bird ringing will celebrate its first century of existence. Started mainly to investigate bird movements, bird ringing has become a much more flexible method to study different aspects of bird biology. Bird ringing can only be properly organised if an effective international co-operation exists. In Europe, this co-ordination is ensured by EURING, made of 35 national ringing centres; sister organisations exist in other parts of the world (like Africa, Australia, U.S. and Canada), sharing the same aims and problems. This RTD is mainly targeted to ornithologists involved with the co-ordination of bird ringing stations and national centres world-wide. Common aspects of the organisation of ringing activities, as well as of the potential ringing has and will have in the future in addressing major scientific questions in Ornithology will be taken into account. The advisability of setting up a standing committee on bird ringing within the IOC will be discussed, and the project of creating a world-wide organisation of ringing schemes in order to further improve communication and exchange of experiences will also be addressed. This new organisation would be formally founded in 1999, when an international conference organised by EURING to celebrate the first 100 years of bird ringing will be held in Denmark.

  9. Present and future of scientific bird ringing

    USGS Publications Warehouse

    Spina, F.; Tautin, J.; Adams, N.J.; Slotow, R.H.

    1999-01-01

    In 1999 scientific bird ringing will celebrate its first century of existence. Started mainly to investigate bird movements, bird ringing has become a much more flexible method to study different aspects of bird biology. Bird ringing can only be properly organised if an effective international co-operation exists. In Europe, this co-ordination is ensured by EURING, made of 35 national ringing centres; sister organisations exist in other parts of the world (like Africa, Australia, U.S. and Canada), sharing the same aims and problems. This RTD is mainly targeted to ornithologists involved with the co-ordination of bird ringing stations and national centres world-wide. Common aspects of the organisation of ringing activities, as well as of the potential ringing has and will have in the future in addressing major scientific questions in Ornithology will be taken into account. The advisability of setting up a standing committee on bird ringing within the IOC will be discussed, and the project of creating a world-wide organisation of ringing schemes in order to further improve communication and exchange of experiences will also be addressed. This new organisation would be formally founded in 1999, when an international conference organised by EURING to celebrate the first 100 years of bird ringing will be held in Denmark.

  10. Boom and Bust Cycles in Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.; Meinke, B. K.; Sremcevic, M.; Albers, N.

    2010-10-01

    7/16/10 12:23 PM UVIS occultation data show clumping in Saturn's F ring and at the B ring outer edge, indicating aggregation and disaggregation at these locations perturbed by Mimas and Prometheus. Timescales range from hours to months. The maximum clumping lags the moon by π in the forcing frame. This indicates a direct relation between the moon and the ring clumping. We propose that the collective behavior of the ring particles resembles a predator-prey system: the aggregate mean size is the prey, which feeds the velocity dispersion; conversely, increasing dispersion breaks up the aggregates. For realistic values of the parameters this creates a limit cycle behavior, as for the ecology of foxes and hares or the boom-bust economic cycle. Solving for the long-term behavior of this forced system gives a periodic response at the perturbing frequency, with a phase lag consistent with the UVIS occultation measurements. We conclude that the agitation by the moons at both these locations in the F ring and at the B ring outer edge drives aggregation and disaggregation in the forcing frame. This agitation of the ring material allows fortuitous formation of solid objects from the temporary clumps, via stochastic processes like compaction, adhesion, sintering or reorganization that drives the denser parts of the aggregate to the center or ejects the lighter elements. These more persistent objects would then orbit at the Kepler rate. Such processes can create the equinox objects seen at the B ring edge and in the F ring, explain the ragged nature of those ring regions and allow for rare events to aggregate ring particles into solid objects, recycling the ring material and extending the ring lifetime. 7/16/10 12:23 PM 7/16/10 12:23 PM

  11. Boom and Bust Cycles in Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Meinke, B. K.; Sremcevic, M.; Albers, N.

    2010-12-01

    Cassini UVIS occultation data show clumping in Saturn’s F ring and at the B ring outer edge, indicating aggregation and disaggregation at these locations perturbed by Mimas and Prometheus. Timescales range from hours to months. The maximum clumping lags the moon by roughly π in the forcing frame. This indicates a direct relation between the moon and the ring clumping. We propose that the collective behavior of the ring particles resembles a predator-prey system: the aggregate mean size is the prey, which feeds the velocity dispersion; conversely, increasing dispersion breaks up the aggregates. For realistic values of the parameters this creates a limit cycle behavior, as for the ecology of foxes and hares or the boom-bust economic cycle. Solving for the long-term behavior of this forced system gives a periodic response at the perturbing frequency, with a phase lag roughly consistent with the UVIS occultation measurements. We conclude that the agitation by the moons at both these locations in the F ring and at the B ring outer edge drives aggregation and disaggregation in the forcing frame. This agitation of the ring material allows fortuitous formation of solid objects from the temporary clumps, via stochastic processes like compaction, adhesion, sintering or reorganization that drives the denser parts of the aggregate to the center or ejects the lighter elements. These more persistent objects would then orbit at the Kepler rate. Such processes can create the equinox objects seen at the B ring edge and in the F ring, explain the ragged nature of those ring regions and allow for rare events to aggregate ring particles into solid objects, recycling the ring material and extending the ring lifetime.

  12. New dust belts of Uranus: one ring, two ring, red ring, blue ring.

    PubMed

    de Pater, Imke; Hammel, Heidi B; Gibbard, Seran G; Showalter, Mark R

    2006-04-07

    We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/2003 U 1 is probably produced by impacts into the embedded moon Mab, which apparently orbits at a location where nongravitational perturbations favor the survival and spreading of submicron-sized dust. R/2003 U 2 more closely resembles Saturn's G ring, which is red, a typical color for dusty rings.

  13. Wavy, Wiggly Ring

    NASA Image and Video Library

    2012-04-23

    The constant change in Saturn wavy, wiggly F ring is on display in this image obtained by NASA Cassini spacecraft. The image shows a view looking directly down onto the ring with the planet removed from the center.

  14. Saturn Rings in Infrared

    NASA Image and Video Library

    2006-10-11

    This mosaic of Saturn rings was acquired by NASA Cassini visual and infrared mapping spectrometer instrument on Sept. 15, 2006, while the spacecraft was in the shadow of the planet looking back towards the rings

  15. The Inner Rings

    NASA Image and Video Library

    2007-02-01

    The Cassini spacecraft looks toward the innermost region of Saturn rings, capturing from right to left the C and B rings. The dark, inner edge of the Cassini Division is just visible in the lower left corner

  16. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  17. Saturn's F-Ring

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This narrow-angle camera image of Saturn's F Ring was taken through the Clear filter while at a distance of 6.9 million km from Saturn on 8 November 1980. The brightness variations of this tightly-constrained ring shown here indicate that the ring is less uniform in makeup than the larger rings. JPL managed the Voyager Project for NASA's Office of Space Science

  18. Modules over hereditary rings

    SciTech Connect

    Tuganbaev, A A

    1998-04-30

    Let A be a hereditary Noetherian prime ring that is not right primitive. A complete description of {pi}-injective A-modules is obtained. Conditions under which the classical ring of quotients of A is a {pi}-projective A-module are determined. A criterion for a right hereditary right Noetherian prime ring to be serial is obtained.

  19. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  20. Rings Around Uranus

    ERIC Educational Resources Information Center

    Maran, Stephen P.

    1977-01-01

    Events leading up to the discovery of the rings of Uranus are described. The methods used and the logic behind the methods are explained. Data collected to prove the existence of the rings are outlined and theories concerning the presence of planetary rings are presented. (AJ)

  1. Eyeing the E Ring

    NASA Image and Video Library

    2009-12-24

    NASA Cassini spacecraft takes a look at Saturn diffuse E ring which is formed from icy material spewing out of the south pole of the moon Enceladus. The E ring is seen nearly edge-on from slightly above the northern side of Saturn ring plane.

  2. Dusty D Ring

    NASA Image and Video Library

    2014-02-24

    Saturn D ring is easy to overlook since it trapped between the brighter C ring and the planet itself. In this view from NASA Cassini spacecraft, all that can be seen of the D ring is the faint and narrow arc as it stretches from top right of the ima

  3. On certain Hecke rings

    PubMed Central

    Evens, Sam; Bressler, Paul

    1987-01-01

    We examine rings that embed into the smash product of the group algebra of the Weyl group with the field of meromorphic functions on the Cartan subalgebra and are generated by elements that satisfy braid relations. We prove that every such ring is isomorphic to either the Hecke algebra, the nil Hecke ring, or the group algebra of the Weyl group. PMID:16593804

  4. Soft normed rings.

    PubMed

    Uluçay, Vakkas; Şahin, Mehmet; Olgun, Necati

    2016-01-01

    Molodtsov introduced the concept of soft sets, which can be seen as a new mathematical tool for dealing with uncertainty. In this paper, we initiate the study of soft normed rings by soft set theory. The notions of soft normed rings, soft normed ideals, soft complete normed rings are introduced and also several related properties and examples are given.

  5. Saturn's largest ring.

    PubMed

    Verbiscer, Anne J; Skrutskie, Michael F; Hamilton, Douglas P

    2009-10-22

    Most planetary rings in the Solar System lie within a few radii of their host body, because at these distances gravitational accelerations inhibit satellite formation. The best known exceptions are Jupiter's gossamer rings and Saturn's E ring, broad sheets of dust that extend outward until they fade from view at five to ten planetary radii. Source satellites continuously supply the dust, which is subsequently lost in collisions or by radial transport. Here we report that Saturn has an enormous ring associated with its outer moon Phoebe, extending from at least 128R(S) to 207R(S) (Saturn's radius R(S) is 60,330 km). The ring's vertical thickness of 40R(S) matches the range of vertical motion of Phoebe along its orbit. Dynamical considerations argue that these ring particles span the Saturnian system from the main rings to the edges of interplanetary space. The ring's normal optical depth of approximately 2 x 10(-8) is comparable to that of Jupiter's faintest gossamer ring, although its particle number density is several hundred times smaller. Repeated impacts on Phoebe, from both interplanetary and circumplanetary particle populations, probably keep the ring populated with material. Ring particles smaller than centimetres in size slowly migrate inward and many of them ultimately strike the dark leading face of Iapetus.

  6. Activation of aldehydes by exocyclic iridium(i)-η(4):π(2)-diene complexes derived from 1,3-oxazolidin-2-ones.

    PubMed

    Padilla, Rosa; Salazar-Pereda, Verónica; Mendoza-Espinosa, Daniel; Vásquez-Pérez, José M; Andrade-López, Noemí; Tamariz, Joaquín; Alvarado-Rodríguez, José G; Cruz-Borbolla, Julián

    2016-11-14

    The Ir(i) complexes [Tp(Me2)Ir(η(4)-1,4-diene)] 2b and 2c react thermally with a variety of aromatic aldehydes, 3a-e, to generate the metallabicyclic compounds 4e-k and the Fischer-type carbenes 5a-b in moderate yields. These reactions are proposed to take place with the initial formation of η(1)-aldehyde adducts as key intermediates. The formation of the metallabicyclic compounds 4e-k involves a formal decarboxylation process at the exo-2-oxazolidinone diene and an ortho metallation of the aromatic ring. The generation of the Fischer-type carbenes 5a-b is the result of a series of metal-based rearranged intermediates with no decarboxylation observed. Treatment of the η(4)-diene complex 2b with a variety of Lewis bases induces a change in the binding mode of the diene ligand from η(4):π(2) to η(2):σ(2) to form the Ir(iii) derivatives 6b-d of composition Tp(Me2)Ir-(η(4):π(2)-1,4-diene)(L) (L = CO, MeCN, and C5H5N). A study of reactions of complex 2b with either mono- or poly-deuterated aldehydes was performed to understand the mechanisms of such processes. The results of these studies were used to determine plausible formation mechanisms of the metallabicyclic compounds 4e-4k and Fischer-type carbenes 5a-b compound series. These mechanisms were corroborated by density functional theory (DFT) calculations of the free energy profiles.

  7. Further structural optimization of cis-(6-benzhydryl-piperidin-3-yl)-benzylamine and 1,4-diazabicyclo[3.3.1]nonane derivatives by introducing an exocyclic hydroxyl group: interaction with dopamine, serotonin, and norepinephrine transporters.

    PubMed

    Mishra, Manoj; Kolhatkar, Rohit; Zhen, Juan; Parrington, Ingrid; Reith, Maarten E A; Dutta, Aloke K

    2008-03-15

    Our earlier effort to develop constrained analogues of flexible piperidine derivatives for monoamine transporters led to the development of a series of 3,6-disubstituted piperidine derivatives, and a series of 4,8-disubstituted 1,4-diazabicyclo[3.3.1]nonane derivatives. In further structure-activity relationship (SAR) studies on these constrained derivatives, several novel analogues were developed where an exocyclic hydroxyl group was introduced on the N-alkyl-aryl side chain. All synthesized derivatives were tested for their affinities for the dopamine transporter (DAT), serotonin (5-HT) transporter (SERT), and norepinephrine transporter (NET) in the brain by measuring their potency in inhibiting the uptake of [(3)H]DA, [(3)H]5-HT, and [(3)H]NE, respectively. Compounds were also tested for their binding potency at the DAT by their ability to inhibit binding of [(3)H]WIN 35,428. The results indicated that position of the hydroxyl group on the N-alkyl side chain is important along with the length of the side chain. In general, hydroxyl derivatives derived from more constrained bicyclic diamines exhibited greater selectivity for interaction with DAT compared to the corresponding 3,6-disubstituted diamines. In the current series of molecules, compound 11b with N-propyl side chain with the hydroxyl group attached in the benzylic position was the most potent and selective for DAT (K(i)=8.63nM; SERT/DAT=172 and NET/DAT=48.4).

  8. On the solar dust ring(s)

    NASA Astrophysics Data System (ADS)

    Mukai, T.

    Based on a mechanism to form the solar dust ring, it is proved that the observed peak in infrared F-corona cannot be explained by silicate type grains alone. Preliminary analysis on the recent infrared data of the F-corona by Maihara et al. (1984) has suggested that the ring particles have different physical properties compared with the dust grains, which produce the background F-corona.

  9. Monolithic catalyst catalytic converter with catalyst holding expansible retainer ring

    SciTech Connect

    Isogai, K.; Koga, I.; Ohmori, N.; Okamoto, M.; Takeuchi, M.; Takita, N.; Tobi, N.

    1984-05-15

    A catalytic converter includes a tubular casing within which is held a monolithic catalyst body which is generally of a columnar shape. The ends of the monolithic catalyst body are each engaged with a cushion ring, and each cushion ring is engaged with a retainer ring therefor, which is substantially axially fixed within the casing near to an end thereof. The monolithic catalyst body is supported within the casing by axial compressive force present between the retainer rings on the outside, the cushion rings between the retainer rings, and the monolithic catalyst body between the cushion rings. At least one of the retainer rings is formed with a break in a part of its circumference, the two free ends of the retainer ring on the two sides of the break being movable with distortion of the retainer ring through a certain distance, according to changes of temperature of the retainer ring, with respect to one another in the mutual relative direction which causes the overall circumference of the retainer ring to be diminished, so that expansion of the retainer ring when it heats up is adsorbed, and the retainer ring is not subject to kinking or folding when the catalytic converter operates in the hot condition.

  10. Electro-optical hybrid slip ring

    NASA Astrophysics Data System (ADS)

    Hong, En

    2005-11-01

    The slip ring is a rotary electrical interface, collector, swivel or rotary joint. It is a physical system that can perform continuous data transfer and data exchange between a stationary and a rotating structure. A slip ring is generally used to transfer data or power from an unrestrained, continuously rotating electro-mechanical system in real-time, thereby simplifying operations and eliminating damage-prone wires dangling from moving joints. Slip rings are widely used for testing, evaluating, developing and improving various technical equipment and facilities with rotating parts. They are widely used in industry, especially in manufacturing industries employing turbo machinery, as in aviation, shipbuilding, aerospace, defense, and in precise facilities having rotating parts such as medical Computerized Tomography (CT) and MRI scanners and so forth. Therefore, any improvement in slip ring technology can impact large markets. Research and development in this field will have broad prospects long into the future. The goal in developing the current slip ring technology is to improve and increase the reliability, stability, anti-interference, and high data fidelity between rotating and stationary structures. Up to now, there have been numerous approaches used for signal and data transfer utilizing a slip ring such as metal contacts, wires, radio transmission, and even liquid media. However, all suffer from drawbacks such as data transfer speed limitations, reliability, stability, electro-magnetic interference and durability. The purpose of the current research is to break through these basic limitations using an optical solution, thereby improving performance in current slip ring applications. This dissertation introduces a novel Electro-Optical Hybrid Slip Ring technology, which makes "through the air" digital-optical communication between stationary and rotating systems a reality with high data transfer speed, better reliability and low interference susceptibility

  11. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring

  12. Cassini RADAR Backscatter Measurements of Saturn Rings

    NASA Astrophysics Data System (ADS)

    West, R. D.; Janssen, M. A.; Cuzzi, J. N.; Anderson, Y. Z.; Hamilton, G.

    2016-12-01

    The Cassini mission is now heading into its last year of observations. Part of the mission plan includes orbits that bring the spacecraft close to Saturn's rings prior to deorbiting into Saturn's atmosphere. First, a series of F-ring orbits will cross the ring plane just outside of the F-ring, and then a series of Proximal orbits will cross the ring plane inside of the D-ring - just above the cloud tops. These orbits are providing a unique opportunity to obtain backscatter measurements and relatively high-resolution brightness temperature measurements from the rings. In one F-ring orbit and three Proximal orbits, the spacecraft will scan the rings with the radar central beam and obtain backscatter measurements as a function of radial distance with some variation of incidence angle. These radar observations will be designed to sweep the A through C rings with varying bandwidth chirps selected to optimize the tradeoff between radial resolution and measurement variance. Pulse compression will deliver radial resolutions varying from about 200 m to around 4 km depending on the bandwidth used. These measurements will provide a 1-D profile of backscatter obtained at 2.2 cm wavelength that will complement similar passive profiles obtained at optical, infrared, and microwave wavelengths. This presentation will summarize the detailed designs and tradeoffs made for these observations. Such measurements will further constrain and inform models of the composition and structure of the ring particle distributions. This work is supported by the NASA Cassini Program at JPL - CalTech.

  13. Surge in the Ring

    NASA Image and Video Library

    2016-08-29

    An ethereal, glowing spot appears on Saturn's B ring in this view from NASA's Cassini spacecraft. There is nothing particular about that place in the rings that produces the glowing effect -- instead, it is an example of an "opposition surge" making that area on the rings appear extra bright. An opposition surge occurs when the Sun is directly behind the observer looking toward the rings. The particular geometry of this observation makes the point in the rings appear much, much brighter than would otherwise be expected. This view looks toward the sunlit side of the rings from about 28 degrees above the ring plane. The image was taken in visible light with the Cassini wide-angle camera on June 26, 2016. The view was acquired at a distance of approximately 940,000 miles (1.5 million kilometers) from the rings and at a Sun-ring-spacecraft, or phase, angle of 0 degrees. Image scale on the rings at center is 56 miles (90 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20496

  14. Traceable Ring Signature

    NASA Astrophysics Data System (ADS)

    Fujisaki, Eiichiro; Suzuki, Koutarou

    The ring signature allows a signer to leak secrets anonymously, without the risk of identity escrow. At the same time, the ring signature provides great flexibility: No group manager, no special setup, and the dynamics of group choice. The ring signature is, however, vulnerable to malicious or irresponsible signers in some applications, because of its anonymity. In this paper, we propose a traceable ring signature scheme. A traceable ring scheme is a ring signature except that it can restrict “excessive” anonymity. The traceable ring signature has a tag that consists of a list of ring members and an issue that refers to, for instance, a social affair or an election. A ring member can make any signed but anonymous opinion regarding the issue, but only once (per tag). If the member submits another signed opinion, possibly pretending to be another person who supports the first opinion, the identity of the member is immediately revealed. If the member submits the same opinion, for instance, voting “yes” regarding the same issue twice, everyone can see that these two are linked. The traceable ring signature can suit to many applications, such as an anonymous voting on a BBS. We formalize the security definitions for this primitive and show an efficient and simple construction in the random oracle model.

  15. GRISM Spectophotometry of the Uranus Ring

    NASA Astrophysics Data System (ADS)

    Smith, Bradford

    1997-07-01

    Details of the near-infrared spectral reflectance of the Uranus rings are poorly known, because of problems associated with the scattered light from the planet. Grism spectroscopy of the brightest part of the Epsilon ring will be made with the planet just outside the field of view. To minimize the glare from Uranus, the observations should made when the widest part of the Epsilon ring is at a position angle of approximately 174 degrees. This is one in a series of observations designed to intercompare the near-infrared spectral reflectivity of dark objects in the solar system. Some record of processes that occurred within the Uranus subnebula may be left on the surfaces of the ring particles or the surface coatings of the associated dark inner satellites.

  16. An absolute radius scale for Saturn's rings

    NASA Technical Reports Server (NTRS)

    Nicholson, Philip D.; Cooke, Maren L.; Pelton, Emily

    1990-01-01

    Radio and stellar occultation observations of Saturn's rings made by the Voyager spacecraft are discussed. The data reveal systematic discrepancies of almost 10 km in some parts of the rings, limiting some of the investigations. A revised solution for Saturn's rotation pole has been proposed which removes the discrepancies between the stellar and radio occultation profiles. Corrections to previously published radii vary from -2 to -10 km for the radio occultation, and +5 to -6 km for the stellar occultation. An examination of spiral density waves in the outer A Ring supports that the revised absolute radii are in error by no more than 2 km.

  17. 1993 Evaluation of steel ring standards for magnetic particle inspection

    SciTech Connect

    Bates, B.; Hagemaier, D.; Petty, J.; Armstrong, C.

    1996-10-01

    The Ketos ring standard manufactured from AISI Type 01 (.90 carbon) tool steel has become part of certain US magnetic particle standards such as MIL-STD-1949. The rings are used to verify system performance and for sensitivity evaluation for magnetic particle materials. Some controversy exists concerning the use of the steel ring as a reference standard for the following reasons: inconsistencies in hole detectability have been noted between various rings caused by differences in magnetic permeability as a result of variations in annealing; the use of magnetic particle indication evaluation for ring standard certification is subject to variations in particle concentration, sensitivity, and visual subjectivity; and the proposed introduction of new materials in the manufacture of ring standards. This report describes an evaluation of rings manufactured of different materials and different annealed states. A suggested method for qualifying a newly manufactured ring as a certified reference standard is also described.

  18. Slowing of Vortex Rings

    NASA Astrophysics Data System (ADS)

    Donnelly, Russell; Bolster, Diogo; Hershberger, Robert

    2008-11-01

    We have investigated the slowing of vortex rings in water which are created with very thin cores. We find that these rings propagate with no measurable change in diameter or core size. The drag appears to be the result of viscous forces on the core. A simple model for this drag describes experimental data in terms of a drag coefficient, which depends only on Reynolds number. Barenghi's group at Newcastle found that the translational velocity of a ring in an inviscid fluid perturbed by Kelvin waves decreases with increasing amplitude of Kelvin waves. This suggests that the velocity of vortex rings in a viscous fluid may well depend on the amplitude of Kelvin waves at the time of formation. Rings with substantial amplitude of Kelvin waves will be expected to move more slowly than rings with little or no Kelvin wave amplitude. We present experimental data confirming this suggestion.

  19. Ring Details on Display

    NASA Image and Video Library

    2016-11-07

    This view from NASA's Cassini spacecraft showcases some of the amazingly detailed structure of Saturn's rings. The rings are made up of many smaller ringlets that blur together when seen from a distance. But when imaged up close, the rings' structures display quite a bit of variation. Ring scientists are debating the nature of these features -- whether they have always appeared this way or if their appearance has evolved over time. This view looks toward the sunlit side of the rings from about 4 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Sept. 24, 2016. The view was acquired at a distance of approximately 283,000 miles (456,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 32 degrees. Image scale is 17 miles (27 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20506

  20. Relation of Nickel Concentrations in Tree Rings to Groundwater Contamination

    NASA Astrophysics Data System (ADS)

    Yanosky, Thomas M.; Vroblesky, Don A.

    1992-08-01

    Increment cores were collected from trees growing at two sites where groundwater is contaminated by nickel. Proton-induced X ray emission spectroscopy was used to determine the nickel concentrations in selected individual rings and in parts of individual rings. Ring nickel concentrations were interpreted on the basis of recent concentrations of nickel in aquifers, historical information about site use activities, and model simulations of groundwater flow. Nickel concentrations in rings increased during years of site use but not in trees outside the contaminated aquifers. Consequently, it was concluded that trees may preserve in their rings an annual record of nickel contamination in groundwater. Tulip trees and oaks contained higher concentrations of nickel than did sassafras, sweet gum, or black cherry. No evidence was found that nickel accumulates consistently within parts of individual rings or that nickel is translocated across ring boundaries.

  1. Relation of nickel concentrations in tree rings to groundwater contamination

    USGS Publications Warehouse

    Yanosky, Thomas M.; Vroblesky, Don A.

    1992-01-01

    Increment cores were collected from trees growing at two sites where groundwater is contaminated by nickel. Proton-induced X ray emission spectroscopy was used to determine the nickel concentrations in selected individual rings and in parts of individual rings. Ring nickel concentrations were interpreted on the basis of recent concentrations of nickel in aquifers, historical information about site use activities, and model simulations of groundwater flow. Nickel concentrations in rings increased during years of site use but not in trees outside the contaminated aquifers. Consequently, it was concluded that trees may preserve in their rings an annual record of nickel contamination in groundwater. Tulip trees and oaks contained higher concentrations of nickel than did sassafras, sweet gum, or black cherry. No evidence was found that nickel accumulates consistently within parts of individual rings or that nickel is translocated across ring boundaries.

  2. Saturn's rings - an overview

    NASA Astrophysics Data System (ADS)

    Cuzzi, J. N.

    2005-08-01

    Saturn's rings embody in their diversity the entire spectrum of ring properties seen across the outer solar system, and remain unique in fundamental ways. The Voyager flybys revealed their complexity in 1980-1981, while groundbased and HST observations have provided important new insights since that time. Since July 2004, when it skimmed only tens of thousands of km over the unlit face of the rings - collecting unique remote and in-situ observations as it entered orbit - Cassini has been fulfilling the long-held dream of understanding Saturn's rings in depth. As of this meeting, if all continues as planned, seven orbits designed specifically with ring observations in mind will have been completed - each providing even better geometric opportunities than an entire Voyager flyby (to a spacecraft with far more powerful instruments than Voyager). Even these represent only a fraction of what the complete mission will tell us about the rings. This talk will review the key properties of the rings, highlight the themes and new insights emerging from recent studies, and serve as a context for new results presented at the meeting. The key properties include the relationship of the rings to their close-in and embedded moons; the composition of the rings and its spatial variation; and the complex radial and vertical structure of the rings, as related to local particle sizes and mass density. The main themes are that several evolutionary processes cause all these to vary - we think substantially - with time, and that the rings may be much younger than Saturn. To achieve our goal of understanding the origin of the rings, we must start from an in-depth characterization of their current state, and peer back through their extensive evolution. Cassini observations, and their theoretical analysis, will ultimately make this possible.

  3. Tiny Mimas, Huge Rings

    NASA Image and Video Library

    2016-11-28

    Saturn's icy moon Mimas is dwarfed by the planet's enormous rings. Because Mimas (near lower left) appears tiny by comparison, it might seem that the rings would be far more massive, but this is not the case. Scientists think the rings are no more than a few times as massive as Mimas, or perhaps just a fraction of Mimas' mass. Cassini is expected to determine the mass of Saturn's rings to within just a few hundredths of Mimas' mass as the mission winds down by tracking radio signals from the spacecraft as it flies close to the rings. The rings, which are made of small, icy particles spread over a vast area, are extremely thin -- generally no thicker than the height of a house. Thus, despite their giant proportions, the rings contain a surprisingly small amount of material. Mimas is 246 miles (396 kilometers) wide. This view looks toward the sunlit side of the rings from about 6 degrees above the ring plane. The image was taken in red light with the Cassini spacecraft wide-angle camera on July 21, 2016. The view was obtained at a distance of approximately 564,000 miles (907,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 31 degrees. Image scale is 34 miles (54 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20509

  4. Faint D Ring

    NASA Image and Video Library

    2015-04-27

    Not all of Saturn's rings are created equal: here the C and D rings appear side-by-side, but the C ring, which occupies the bottom half of this image, clearly outshines its neighbor. The D ring appears fainter than the C ring because it is comprised of less material. However, even rings as thin as the D ring can pose hazards to spacecraft. Given the high speeds at which Cassini travels, impacts with particles just fractions of a millimeter in size have the potential to damage key spacecraft components and instruments. Nonetheless, near the end of Cassini's mission, navigators plan to thread the spacecraft's orbit through the narrow region between the D ring and the top of Saturn's atmosphere. This view looks toward the unilluminated side of the rings from about 12 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2015. The view was acquired at a distance of approximately 372,000 miles (599,000 kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 133 degrees. Image scale is 2.2 miles (3.6 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/pia18313

  5. Saturn's E ring revisited

    NASA Astrophysics Data System (ADS)

    Feibelman, W. A.; Klinglesmith, D. A.

    1980-07-01

    Images of the E ring of Saturn obtained by the image processing of photographs of the 1966 edge-on presentation of the planet's ring plane are presented. Two methods of image enhancement were used: scanning with an image quantizer operated in the derivative mode to enhance contrast and computerized subtraction of a circularly symmetric image of the overexposed Saturn disk. Further photographic and CCD observation confirming the existence of the ring extending to twice the diameter of the A ring, which was not detected by the Pioneer 11 imaging photopolarimeter, is indicated.

  6. Viscosity in Saturn's rings

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.; Shu, F. H.; Cuzzi, J. N.

    1982-01-01

    The technique of estimating the viscosity in Saturn's rings from the damping rate of waves observed to be propagating within the rings is discussed. The wavetrains of attempts using spiral density waves as a diagnostic suffer significant complications that compromise the interpretations. A method that considers the damping of spiral bending waves was used to deduce a kinematic viscosity of 260 (+150, -100) sqcm/sec for the middle of the A ring where bending waves are excited by the 5:3 vertical resonance with Mimas. This value implies upper limits on the particle velocity dispersion and local ring thickness of 0.4 cm/sec and 30 m, respectively.

  7. Modified spiral wound retaining ring

    NASA Technical Reports Server (NTRS)

    Lawson, A. G. (Inventor)

    1980-01-01

    A spiral wound retaining ring with angled ends is described. The ring is crimped at the same angle as the ring ends to maintain a constant thickness dimension. The angling of the ends of the ring and crimp allow the ends to be positioned closer together while maintaining enough clearance to enable insertion and removal of the ring. By reducing the separation distance between the ends a stronger ring results since the double layer area of the ring is maximized.

  8. Effects of Meteoroid Erosion in Planetary Rings

    NASA Technical Reports Server (NTRS)

    Durisen, Richard H.

    1995-01-01

    This grant supported continuing studies of the effects of ballistic transport on the evolution of Saturn's rings. Ballistic transport, as used in this context, refers to the net transport of mass and angular momentum caused by the exchange of meteoroid impact ejecta between neighboring ring regions (Ip 1983, 1984, Morfill et al. 1983, Lissauer 1984, Durisen 1984a,b). The characteristic time scale associated with this process is the gross erosion time t(sub g) the time it would take a ring region to be completed eroded if all impact ejecta were lost. This time scale is estimated to be about 10(exp 5) to 10(exp 6) years for a ring region with normal optical depth tau approximately 1. Earlier work by myself and collaborators developed the physical theory and simulation techniques to model this process (Durisen et al. 1989, Cuzzi and Durisen 1990). Detailed simulations, supported in part by this grant, have demonstrated that ballistic transport can produce observed structures in Saturn's rings, especially at and near the inner edges of the A and B Rings (Durisen et al. 1992, 1996). The structures of interest in the real rings are illustrated in Figures 1 and 2. Most of these structures were previously unexplained. The computational results plus analytic treatments place useful constraints on fundamental ring properties, including the indication of a relatively young ring age less than or equal 10(exp 8) years (see reviews by Nicholson and Dones 1991, Esposito 1993, Cuzzi 1995, and Porco 1995). This grant also supported development of the faster computational algorithms necessary to permit longer evolutions. Resulting simplications in the ballistic transport equations permitted an analytic linear stability analysis (Durisen 1995), which has provided considerable insight into ballistic transport processes and applications to Saturn's rings. All these accomplishments are described in more detail below.

  9. The exocyclic amino group of adenine in Pt(II) and Pd(II) complexes: a critical comparison of the X-ray crystallographic structural data and gas phase calculations.

    PubMed

    Silaghi-Dumitrescu, Radu; Mihály, Béla; Mihály, Timea; Attia, Amr A A; Sanz Miguel, Pablo J; Lippert, Bernhard

    2017-03-17

    A detailed computational (DFT level of theory) study regarding the nature of the exocyclic amino group, N6H2, of the model nucleobase 9-methyladenine (9MeA) and its protonated (9MeAH(+)) and deprotonated forms (9MeA-H), free and metal-complexed, has been conducted. The metals are Pt(II) and Pd(II), bonded to nitrogen-containing co-ligands (NH3, dien, bpy), with N1, N6, and N7 being the metal-binding sites, individually or in different combinations. The results obtained from gas phase calculations are critically compared with X-ray crystallography data, whenever possible. In the majority of cases, there is good qualitative agreement between calculated and experimentally determined C6-N6 bond lengths, but calculated values always show a trend to larger values, by 0.02-0.08 Å. Both methods indicate, with few exceptions, a high degree of double-bond character of C6-N6, consistent with an essentially sp(2)-hybridized N6 atom. The shortest values for C6-N6 distances in X-ray crystal structures are around 1.30 Å. Exceptions refer to cases in which DFT calculations suggest the existence of a hydrogen bond with N6H2 acting as a H bond acceptor, hence a situation with N6 having undergone a substantial hybridization shift toward sp(3). Nevertheless, even in these cases the C6-N6 bond (1.392 Å) is still halfway between a typical C-N single bond (1.48 Å) and a typical C=N double bond (1.28 Å). This scenario is, however, not borne out by X-ray crystallographic results, and is attributed to the absence of counter anions and solvent molecules in the calculated structures.

  10. Neptune's ring system.

    NASA Astrophysics Data System (ADS)

    Porco, C. C.; Nicholson, P. D.; Cuzzi, J. N.; Lissauer, J. J.; Esposito, L. W.

    The authors review the current state of knowledge regarding the structure, particle properties, kinematics, dynamics, origin, and evolution of the Neptune rings derived from Earth-based and Voyager data. Neptune has a diverse system of five continuous rings - 2 broad (Galle and Lassell) and 3 narrow (Adams, Le Verrier, and Arago) - plus a narrow discontinuous ring sharing the orbit of one of its ring-region satellites, Galatea. The outermost Adams ring contains the only arcs observed so far in Voyager images. The five arcs vary in angular extent from ≡1° to ≡10°, and exhibit internal azimuthal structure with typical spatial scales of ≡0.5°. All five lie within ≡40° of longitude. Dust is present throughout the Neptune system and measureable quantities of it were detected over Neptune's north pole. The Adams ring (including the arcs) and the Le Verrier ring contain a significant fraction of dust. The Neptune ring particles are probably red, and may consist of ice "dirtied" with silicates and/or some carbon-bearing material. A kinematic model for the arcs derived from Voyager data, the arcs' physical characteristics, and their orbital geometry and phasing are all roughly in accord with single-satellite arc shepherding by Galatea, though the presence of small kilometer-sized bodies embedded either within the arcs or placed at their Lagrange points may explain some inconsistencies with this model.

  11. EBT ring physics

    SciTech Connect

    Uckan, N.A.

    1980-04-01

    This workshop attempted to evaluate the status of the current experimental and theoretical understanding of hot electron ring properties. The dominant physical processes that influence ring formation, scaling, and their optimal behavior are also studied. Separate abstracts were prepared for each of the 27 included papers. (MOW)

  12. Uranus Ring System

    NASA Image and Video Library

    1996-01-29

    This image captured by NASA's Voyager 2 in 1986 revealed a continuous distribution of small particles throughout the Uranus ring system. This unique geometry, the highest phase angle at which Voyager imaged the rings, allowed us to see lanes of fine dust. http://photojournal.jpl.nasa.gov/catalog/PIA00142

  13. Smoke Ring Physics

    NASA Astrophysics Data System (ADS)

    Huggins, Elisha

    2011-11-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampère's law in an introductory physics course. We discuss these common features.

  14. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  15. Steroidal contraceptive vaginal rings.

    PubMed

    Sarkar, N N

    2003-06-01

    The development of steroid-releasing vaginal rings over the past three decades is reviewed to illustrate the role of this device as an effective hormonal contraceptive for women. Vaginal rings are made of polysiloxane rubber or ethylene-vinyl-acetate copolymer with an outer diameter of 54-60 mm and a cross-sectional diameter of 4-9.5 mm and contain progestogen only or a combination of progestogen and oestrogen. The soft flexible combined ring is inserted in the vagina for three weeks and removed for seven days to allow withdrawal bleeding. Progesterone/progestogen-only rings are kept in for varying periods and replaced without a ring-free period. Rings are in various stages of research and development but a few, such as NuvaRing, have reached the market in some countries. Women find this method easy to use, effective, well tolerated and acceptable with no serious side-effects. Though the contraceptive efficacy of these vaginal rings is high, acceptability is yet to be established.

  16. Smoke Ring Physics

    ERIC Educational Resources Information Center

    Huggins, Elisha

    2011-01-01

    The behavior of smoke rings, tornados, and quantized vortex rings in superfluid helium has many features in common. These features can be described by the same mathematics we use when introducing Ampere's law in an introductory physics course. We discuss these common features. (Contains 7 figures.)

  17. Lower esophageal ring (Schatzki)

    MedlinePlus

    ... narrowed area to stretch the ring. Sometimes, a balloon is placed in the area and inflated, to help widen the ring. Outlook (Prognosis) Swallowing problems may return. You may need repeat treatment. When to Contact a Medical Professional Call your health care provider if you ...

  18. Contactless Magnetic Slip Ring

    NASA Technical Reports Server (NTRS)

    Kumagai, Hiroyuki (Inventor); Deardon, Joe D. (Inventor)

    1997-01-01

    A contactless magnetic slip ring is disclosed having a primary coil and a secondary coil. The primary and secondary coils are preferably magnetically coupled together, in a highly reliable efficient manner, by a magnetic layered core. One of the secondary and primary coils is rotatable and the contactless magnetic slip ring provides a substantially constant output.

  19. Rings of Neptune

    NASA Image and Video Library

    1999-07-25

    These two 591-second exposures of the rings of Neptune were taken with the clear filter by the NASA Voyager 2 wide-angle camera on Aug. 26, 1989. The two main rings are clearly visible and appear complete over the region imaged.

  20. Illustration of Saturn's Rings

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This illustration shows a close-up of Saturn's rings. These rings are thought to have formed from material that was unable to form into a Moon because of tidal forces from Saturn, or from a Moon that was broken up by Saturn's tidal forces.

  1. Birth Control Ring

    MedlinePlus

    ... It? The birth control ring is a soft, flexible, doughnut-shaped ring about 2 inches (5 centimeters) in diameter. It is inserted into the vagina, where it slowly releases hormones — the chemicals the body makes to control organ function — through the vaginal wall into the ...

  2. A-ring Propeller

    NASA Image and Video Library

    2010-08-26

    A propeller-shaped structure, created by an unseen moon, can be seen in Saturn A ring and looks like a small, dark line interrupting the bright surrounding ring material in the upper left of this image taken by NASA Cassini spacecraft.

  3. Telemetry carrier ring and support

    NASA Technical Reports Server (NTRS)

    Wakeman, Thomas G. (Inventor)

    1992-01-01

    A telemetry carrier ring for use in a gas turbine engine includes an annular support ring connected to the engine and an annular carrier ring coupled to the support ring, each ring exhibiting different growth characteristics in response to thermal and mechanical loading. The carrier ring is coupled to the support ring by a plurality of circumferentially spaced web members which are relatively thin in an engine radial direction to provide a predetermined degree of radial flexibility. the web members have a circumferential width and straight axial line of action selected to transfer torque and thrust between the support ring and the carrier ring without substantial deflection. The use of the web members with radial flexibility provides compensation between the support ring and the carrier ring since the carrier ring grows at a different rate than the supporting ring.

  4. Jupiter's Gossamer Rings Explained.

    NASA Astrophysics Data System (ADS)

    Hamilton, D. P.

    2003-05-01

    Over the past several years, Galileo measurements and groundbased imaging have drastically improved our knowledge of Jupiter's faint ring system. We now recognize that the ring consists of four components: a main ring 7000km wide, whose inner edge blossoms into a vertically-extended halo, and a pair of more tenuous Gossamer rings, one associated with each of the small moons Thebe and Amalthea. When viewed edge on, the Gossamer rings appear as diaphanous disks whose thicknesses agree with the vertical excursions of the inclined satellites from the equatorial plane. In addition, the brightness of each Gossamer ring drops off sharply outside the satellite orbits. These correlations allowed Burns etal (1999, Science, 284, 1146) to argue convincingly that the satellites act as sources of the dusty ring material. In addition, since most material is seen inside the orbits of the source satellites, an inwardly-acting dissipative force such as Poynting-Robertson drag is implicated. The most serious problem with this simple and elegant picture is that it is unable to explain the existence of a faint swath of material that extends half a jovian radius outward from Thebe. A key constraint is that this material has the same thickness as the rest of the Thebe ring. In this work, we identify the mechanism responsible for the outward extension: it is a shadow resonance, first investigated by Horanyi and Burns (1991, JGR, 96, 19283). When a dust grain enters Jupiter's shadow, photoelectric processes shut down and the grain's electric charge becomes more negative. The electromagnetic forces associated with the varying charge cause periodic oscillations in the orbital eccentricity and semimajor axis as the orbital pericenter precesses. This results in a ring which spreads both inward and outward of its source satellite while preserving its vertical thickness - just as is observed for the Thebe ring. Predictions of the model are: i) gaps of micron-sized material interior to Thebe and

  5. Jupiter's Rings: Sharpest View

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The New Horizons spacecraft took the best images of Jupiter's charcoal-black rings as it approached and then looked back at Jupiter. The top image was taken on approach, showing three well-defined lanes of gravel- to boulder-sized material composing the bulk of the rings, as well as lesser amounts of material between the rings. New Horizons snapped the lower image after it had passed Jupiter on February 28, 2007, and looked back in a direction toward the sun. The image is sharply focused, though it appears fuzzy due to the cloud of dust-sized particles enveloping the rings. The dust is brightly illuminated in the same way the dust on a dirty windshield lights up when you drive toward a 'low' sun. The narrow rings are confined in their orbits by small 'shepherding' moons.

  6. Jupiter Ring, With Orion

    NASA Image and Video Library

    2017-05-25

    As NASA's Juno spacecraft flew through the narrow gap between Jupiter's radiation belts and the planet during its first science flyby, Perijove 1, on August 27, 2016, the Stellar Reference Unit (SRU-1) star camera collected the first image of Jupiter's ring taken from the inside looking out. The bright bands in the center of the image are the main ring of Jupiter's ring system. While taking the ring image, the SRU was viewing the constellation Orion. The bright star above the main ring is Betelgeuse, and Orion's belt can be seen in the lower right. Juno's Radiation Monitoring Investigation actively retrieves and analyzes the noise signatures from penetrating radiation in the images of the spacecraft's star cameras and science instruments at Jupiter. https://photojournal.jpl.nasa.gov/catalog/PIA21644

  7. Radio Emission from Saturn's Rings: Polarization

    NASA Astrophysics Data System (ADS)

    Molnar, L. A.; Dunn, D. E.

    2002-09-01

    We are pursuing a systematic program of observing and modeling the radio emission from Saturn's rings over a range of wavelengths and ring inclinations. In our earlier reports we have presented a number total intensity maps along with results from our Monte Carlo radiative transfer code, simrings. This has been a fruitful test of particle spatial distribution within the rings: in particular evidence of wake structure in the A ring and of a near monolayer in the C ring. In this contribution we present our first maps of polarized intensity. Such observations offer independent information about the nature of the ring particles. In particular, Grossman (Ph.D. thesis, 1990) showed that the orientation of the position angle of the polarization of the rings is in direct conflict with the predictions of Mie scattering. We will present several polarized maps, discuss some of the subtleties of producing such maps (in particular the tradeoff between angular resolution and reliable intensities), and suggest possible approaches for modeling of the polarized emission. This work was supported in part by a grant from Research Corporation.

  8. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  9. Cellular Automata Models of Ring Dynamics

    NASA Astrophysics Data System (ADS)

    Gravner, Janko

    This paper describes three models arising from the theory of excitable media, whose primary visual feature are expanding rings of excitation. Rigorous mathematical results and experimental/computational issues are both addressed. We start with the much-studied Greenberg-Hastings model (GHM) in which the rings are very short-lived, but they do have a transient percolation property. By contrast, in the model we call annihilating nested rings (ANR), excitation centers only gradually lose strength, i.e., each time they become inactive (and then stay so forever) with a fixed probability; we show how the long-term global connectivity properties of the set of excited sites undergo a phase transition. Second part of the paper is devoted to digital boiling (DB) in which new rings spontaneously appear at rested sites with a positive probability. We focus on such (related) issues as convergence to equilibrium, equilibrium excitation level and success of the basic coupling.

  10. Cellular automata models of ring dynamics

    SciTech Connect

    Gravner, J.

    1996-12-01

    This paper describes three models arising from the theory of excitable media, whose primary visual feature are expanding rings of excitation. Rigorous mathematical results and experimental/computational issues are both addressed. We start with the much-studied Greenberg-Hastings model (GHM) in which the rings are very short-lived, but they do have a transient percolation property. By contrast, in the model we call annihilating nested rings (ANR), excitation centers only gradually lose strength, i.e., each time they become inactive (and then stay so forever) with a fixed probability; we show how the long-term global connectivity properties of the set of excited sites undergo a phase transition. Second part of the paper is devoted to digital boiling (DB) in which new rings spontaneously appear at rested sites with a positive probability. We focus on such (related) issues as convergence to equilibrium, equilibrium excitation level and success of the basic coupling.

  11. Oral hyaline ring granuloma: a case report.

    PubMed

    Naik, Veena V; Mishra, Mithelesh; Pilli, Ganga S

    2012-11-01

    An unusual granulomatous inflammatory lesion characterised by the presence of ring shaped hyaline bodies accompanied by foreign body giant cell reaction has been mentioned in the literature. A lack of agreement exists on the nature of these hyaline rings. Opinions ranging from their being hyaline degenerative blood vessels to remains of leguminous cells have been postulated. Although the nature and origin of these bodies is uncertain, there is now considerable evidence that they represent, at least in part, vegetable material, especially pulses, that have been implanted in the tissues. An inflammatory oral lesion in a 17-years-old male patient caused due to traumatic implantation of the vegetable matter (sugar cane) has been reported in this paper. Based on the histological finding of a granulation tissue surrounding a hyaline ring the lesion was diagnosed as hyaline ring granuloma.

  12. Light-induced yellowing of selectively 13C-enriched dehydrogenation polymers (DHPs). Part 2, NMR assignments and photoyellowing of aromatic ring 1-, 3-, 4-, and 5-13C DHPs

    Treesearch

    Jim Parkas; Magnus Paulsson; Terashima Noritsugu; Ulla Westermark; Sally Ralph

    2004-01-01

    Light-induced yellowing of lignocellulosicmaterials has been studied using 13C-enriched DHP (dehydrogenation polymer), selectively 13C-enriched at positions 1, 3, 4, and 5 in the aromatic ring, and quantitative solution state 13C NMR spectroscopy. The NMR study confirmed the results of previous studies using side-chain labeled DHP, mainly that coniferyl alcohol end...

  13. Earth: A Ringed Planet?

    NASA Astrophysics Data System (ADS)

    Hancock, L. O.; Povenmire, H.

    2010-12-01

    Among the most beautiful findings of the Space Age have been the discoveries of planetary rings. Not only Saturn but also Jupiter, Uranus and Neptune have rings; Saturn’s ring system has structures newly discovered; even Saturn's moon Rhea itself has a ring. All these are apparently supplied by material from the planetary moons (Rhea's ring by Rhea itself). The question naturally arises, why should the Earth not have a ring, and on the other hand, if it does, why has it not been observed? No rings have yet been observed in the inner solar system, but after all, rings in the inner solar system might simply tend to be fainter and more transient than those of the outer solar system: the inner solar system is more affected by the solar wind, and the Sun’s perturbing gravitational influence is greater. J.A. O’Keefe first suggested (1980) that Earth might have a ring system of its own. An Earth ring could account for some climate events. O’Keefe remarked that formation or thickening of a ring system in Earth’s equatorial plane could drive glaciation by deepening the chill of the winter hemisphere. (It is very well established that volcanic dust is an effective agent for the extinction of sunlight; this factor can be overwhelmingly apparent in eclipse observations.) O’Keefe died in 2000 and the speculation was not pursued, but the idea of an Earth ring has a prima facie reasonableness that calls for its renewed consideration. The program of this note is to hypothesize that, as O’Keefe proposed: (a) an Earth ring system exists; (b) it affects Earth's weather and climate; (c) the tektite strewn fields comprise filaments of the ring fallen to Earth's surface on various occasions of disturbance by comets or asteroids. On this basis, and drawing on the world's weather records, together with the Twentieth Century Reanalysis by NCEP/CIRES covering the period 1870-2010 and the geology of the tektite strewn fields, we herein propose the hypothesized Earth ring

  14. Seal ring installation tool

    NASA Technical Reports Server (NTRS)

    Haselmaier, L. Haynes (Inventor)

    2004-01-01

    A seal ring tool that allows an installer to position a primary seal ring between hub ends of pipe flanges that are being assembled together. The tool includes a pivoting handle member and extension arms attached to the pivoting handle member. The ends of the arms have side indentation type longitudinal grooves angled toward one another for holding the primary seal ring in place between the hubs of respective pipes that are to be attached together. The arms of the tool can also have flat sides that can be used to abut against an optional second larger seal that is supported within a groove in one of the hub ends so that the second hub end can then be moved against the other side of the primary seal ring. Once the seal ring is positioned between the pipe hubs, the pipe hubs can be moved about the seal ring due to the flat sides of the arms of the tool. The tool eliminates the chances of damaging and contaminating seal rings being installed within pipe hubs that are being attached to one another.

  15. Gored of the Rings

    NASA Image and Video Library

    2014-06-09

    Prometheus is caught in the act of creating gores and streamers in the F ring. Scientists believe that Prometheus and its partner-moon Pandora are responsible for much of the structure in the F ring as shown by NASA Cassini spacecraft. The orbit of Prometheus (53 miles, or 86 kilometers across) regularly brings it into the F ring. When this happens, it creates gores, or channels, in the ring where it entered. Prometheus then draws ring material with it as it exits the ring, leaving streamers in its wake. This process creates the pattern of structures seen in this image. This process is described in detail, along with a movie of Prometheus creating one of the streamer/channel features, in PIA08397. This view looks toward the sunlit side of the rings from about 8.6 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Feb. 11, 2014. The view was acquired at a distance of approximately 1.3 million miles (2.1 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 147 degrees. Image scale is 8 miles (13 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18270

  16. Gibbs Ringing in Diffusion MRI

    PubMed Central

    Veraart, Jelle; Fieremans, Els; Jelescu, Ileana O.; Knoll, Florian; Novikov, Dmitry S.

    2016-01-01

    Purpose To study and reduce the effect of Gibbs ringing artifact on computed diffusion parameters. Methods We reduce the ringing by extrapolating the k-space of each diffusion weighted image beyond the measured part by selecting an adequate regularization term. We evaluate several regularization terms and tune the regularization parameter to find the best compromise between anatomical accuracy of the reconstructed image and suppression of the Gibbs artifact. Results We demonstrate empirically and analytically that the Gibbs artifact, which is typically observed near sharp edges in magnetic resonance images, has a significant impact on the quantification of diffusion model parameters, even for infinitesimal diffusion weighting. We find the second order total generalized variation to be a good choice for the penalty term to regularize the extrapolation of the k-space, as it provides a parsimonious representation of images, a practically full suppression of Gibbs ringing, and the absence of staircasing artifacts typical for total variation methods. Conclusions Regularized extrapolation of the k-space data significantly reduces truncation artifacts without compromising spatial resolution in comparison to the default option of window filtering. In particular, accuracy of estimating diffusion tensor imaging and diffusion kurtosis imaging parameters improves so much that unconstrained fits become possible. PMID:26257388

  17. An Arc in Saturn's G Ring

    NASA Astrophysics Data System (ADS)

    Burns, Joseph A.; Hedman, M.; Tiscareno, M.; Porco, C.; Jones, G.; Roussos, E.; Krupp, N.

    2006-09-01

    The G ring is a narrow, faint ring located between the orbits of Janus and Mimas. Approximately 4000 km wide, it has a strongly asymmetric brightness profile with a sharp inner edge between 167,000 km and 168,000 km from Saturn's center and a more diffuse outer part. In Cassini images, a portion of the ring contains a bright arc that abuts the G-ring's inner edge and extends over 30 degrees in longitude. By tracking this arc over the first two years of the Cassini Mission, we find its orbital period is 0.80813 day, corresponding to a semi-major axis of 167,496 km. Since this location places the arc within 6 km of the Mimas 7:6 Co-rotation Eccentricity Resonance and within 12 km of the Mimas 7:6 Inner Lindblad Resonance, the arc is likely confined in longitude by Mimas just as Neptune's ring arcs are held in place by Galatea. The arc's longitude relative to Mimas is consistent with this model. Cassini now has the opportunity to study the dynamics of this sort of system in detail over a period of years. The arc, which may be the debris of a fragmented moon, may also supply the particles found in the rest of the G ring; micron-sized grains drift outwards by non-gravitational processes in this region. The G-ring is responsible for a broad, relatively modest decrease in the fluxes of magnetospheric charged particles. When Cassini passed over the G ring in the vicinity of the arc, on September 5, 2005, the MIMI instrument detected a particularly sharp and deep charged particle absorption signature. Such a pronounced charged particle absorption was not seen in the other G-ring passages that occurred longitudinally far from the arc. The nature of this absorption provides constraints on the population of large particles in this arc.

  18. Low tilt angle photometry and the thickness of Saturn's rings

    NASA Technical Reports Server (NTRS)

    Lumme, K.; Irvine, W. M.

    1979-01-01

    Nine photographic plates taken by Focas and Dollfus (1969) at the moment of the 1966 passage of the earth through the ring plane of Saturn have been remeasured. The value 0.8 (+2.3, -0.8) km is obtained for the ring thickness. The observed transmitted radiation through the rings at two distances from the planet suggests that there are density fluctuations in Ring A with the low density areas having an optical thickness less than 0.13. The radiation reflected by the outermost part of the ring layer can be explained in terms of particles similar to those in the bulk of the rings. The time of the passage of the earth through the ring plane was found to be December 18 at 07h plus or minus 4h UT in 1966.

  19. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  20. Dynamics of the Uranian Rings

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    Some of the problems of the shepherding satellite model of Goldreich ant tremaine are discussed. The following topics are studied: (1) optical depths of the all the observed narrow rings; (2) satellite and ring separation timescales; (3) ring edge sharpness; (4) shock formation in narrow rings; (5) the existence of small satellites near the Uranian rings; and (6) the apse and node alignments of the eccentric and inclined rings.

  1. Dynamics of planetary rings

    NASA Astrophysics Data System (ADS)

    Araki, S.

    1991-02-01

    The modeling of the dynamics of particle collisions within planetary rings is discussed. Particles in the rings collide with one another because they have small random motions in addition to their orbital velocity. The orbital speed is roughly 10 km/s, while the random motions have an average speed of about a tenth of a millimeter per second. As a result, the particle collisions are very gentle. Numerical analysis and simulation of the ring dynamics, performed with the aid of a supercomputer, is outlined.

  2. Theodolite Ring Lights

    NASA Technical Reports Server (NTRS)

    Clark, David

    2006-01-01

    Theodolite ring lights have been invented to ease a difficulty encountered in the well-established optical-metrology practice of using highly reflective spherical tooling balls as position references. A theodolite ring light produces a more easily visible reflection and eliminates the need for an autocollimating device. A theodolite ring light is a very bright light source that is well centered on the optical axis of the instrument. It can be fabricated, easily and inexpensively, for use on a theodolite or telescope of any diameter.

  3. Heavy ion storage rings

    SciTech Connect

    Schuch, R.

    1987-01-01

    A brief overview of synchrotron storage rings for heavy ions, which are presently under construction in different accelerator laboratories is given. Ions ranging from protons up to uranium ions at MeV/nucleon energies will be injected into these rings using multiturn injection from the accelerators available or being built in these laboratories. After injection, it is planned to cool the phase space distribution of the ions by merging them with cold electron beams or laser beams, or by using stochastic cooling. Some atomic physics experiments planned for these rings are presented.

  4. Alternative parallel ring protocols

    NASA Technical Reports Server (NTRS)

    Mukkamala, R.; Foudriat, E. C.; Maly, Kurt J.; Kale, V.

    1990-01-01

    Communication protocols are know to influence the utilization and performance of communication network. The effect of two token ring protocols on a gigabit network with multiple ring structure is investigated. In the first protocol, a mode sends at most one message on receiving a token. In the second protocol, a mode sends all the waiting messages when a token is received. The behavior of these protocols is shown to be highly dependent on the number of rings as well as the load in the network.

  5. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025870 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  6. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025872 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  7. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025866 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  8. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025868 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  9. Hopkins with SPHERES RINGS

    NASA Image and Video Library

    2013-11-04

    ISS037-E-025879 (4 Nov. 2013) --- In the International Space Station?s Kibo laboratory, NASA astronaut Michael Hopkins, Expedition 37 flight engineer, conducts a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  10. Photochemical studies of alkylammonium molybdates. Part 12. O→Mo charge-transfer triplet-states-initiated self-assembly to {Mo154} ring- and tube-molybdenum-blues

    NASA Astrophysics Data System (ADS)

    Yamase, T.; Prokop, P.; Arai, Y.

    2003-08-01

    The chemically induced dynamic electron-spin-polarization technique is employed in order to investigate the primary steps of the photoredox reaction between polyoxomolybdates and alkylammonium cations as both proton and electron-donors in solutions. An observation of emissive electron-spin-polarization signals of alkylamino radical cations for the photoredox reaction between polyoxomolybdates and alkylammonium cations in solutions reveals that the O→Mo ligand-to-metal charge-transfer triplet states are involved in the transfers of both proton and electron from alkylammonium cation to polyoxomolybdate anions. Prolonged photolysis of aqueous solutions containing [Mo36O112(H2O)16]8-, [iPrNH3]+, and LaCl3 at pH 1.0 leads to formation of two kinds of {Mo154} molybdenum-blues, [Mo28VMo126VIO462H28(H2O)70]·156.5H2O (1) and [iPrNH3]8 [Mo28VMo126VIO458H12(H2O)66]·127H2O (2), which were X-ray crystallographically characterized. The former exhibits the intact car-tire-shaped {Mo154} ring structure (with thickness of about 1.1 nm and with outer- and inner-rings of approximately 3.5- and 2.3-nm diameters, respectively) derived formally from the dehydrated cyclic heptamerization of four-electron reduced building blocks of {Mo22} (≡[Mo4VMo18VIO70H12(H2O)10]) with overall symmetry of D7d. The anion for the latter, [Mo28VMo126VIO458H12(H2O)66]8- (2a), exhibits a nanotube structure of {Mo154} rings, each inner ring of which contains a bis(μ-oxo)-linkaged [MoO2(μ-O)(μ-H2O)MoO2]2+ unit replacing one of seven [Mo(H2O)O2(μ-O)Mo(H2O)O2]2+linker units. The neighboring {Mo154} rings are connected by six Mo-O-Mo bridge between inner-rings consisting of 7 head- and 14 linkers-MoO6 octahedra for each.

  11. Scintillating C Ring

    NASA Image and Video Library

    2007-01-16

    Both luminous and translucent, the C ring sweeps out of the darkness of Saturn's shadow and obscures the planet at lower left. The ring is characterized by broad, isolated bright areas, or "plateaus," surrounded by fainter material. This view looks toward the unlit side of the rings from about 19 degrees above the ringplane. North on Saturn is up. The dark, inner B ring is seen at lower right. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 15, 2006 at a distance of approximately 632,000 kilometers (393,000 miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 56 degrees. Image scale is 34 kilometers (21 miles) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA08855

  12. Ring of Stellar Fire

    NASA Image and Video Library

    2014-10-22

    This image from NASA Spitzer Space Telescope shows where the action is taking place in galaxy NGC 1291. The outer ring, colored red, is filled with new stars that are igniting and heating up dust that glows with infrared light.

  13. Outer B Ring Edge

    NASA Image and Video Library

    2004-12-03

    This image NASA Cassini spacecraft shows subtle, wavelike patterns, hundreds of narrow features resembling a record grooves in Saturn outer B-ring, and a noticeable abrupt change in overall brightness beyond the dark gap near the right.

  14. A-Ring Structures

    NASA Image and Video Library

    2010-09-23

    Several structures in Saturn A ring are exposed near the Encke Gap in this image captured by NASA Cassini spacecraft. A peculiar kink can be seen in one particularly bright ringlet at the bottom right.

  15. Ring Shadows on Janus

    NASA Image and Video Library

    2009-12-23

    Sunlight passing through the Cassini Division between Saturn A and B rings sweeps across and illuminates the surface of the moon Janus in this image captured by NASA Cassini spacecraft. Go to the Photojournal to view the animation.

  16. View of Saturn Rings

    NASA Image and Video Library

    1999-01-18

    This view shows some detail and differences in the complex system of rings. This was one of the first pictures obtained once NASA Voyager 2 resumed returning images Aug. 29, 1979 after its scan platform was commanded to view Saturn.

  17. Rings and Waves

    NASA Image and Video Library

    2013-09-30

    Saturn A ring is decorated with several kinds of waves. NASA Cassini spacecraft has captured a host of density waves, a bending wave, and the edge waves on the edge of the Keeler gap caused by the small moon Daphnis.

  18. Wisps Under the Rings

    NASA Image and Video Library

    2015-12-28

    Dione beautiful wispy terrain is brightly lit alongside Saturn elegant rings in this image captured by NASA Cassini spacecraft. The wisps are relatively young fractures on the trailing hemisphere of Dione icy surface.

  19. Warm core rings

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    Gulf stream phenomena have been the focus of numerous studies by U.S. and Canadian oceanographic laboratories. Two years ago, observations of warm core rings associated with the Gulf Stream were reported in The Oceanography Report, (November 2, 1982, p. 834). It was noted then that the structure of warm core rings can undergo rapid transformation. Recently, a multidisciplinary group of physical and biological oceanographic institutions has examined the evolution of warm core rings in detail [Nature, 308, pp. 837-840, 1984]. The study has involved research vessels Endeavor, Atlantis II, and Albatross IV for surface measurements of temperature, salinity, and for measurement surface pigments to assess the concentration of marine plants. The results are that even though warm core rings are often very stable, undergoing only slow changes, it turns out that major alterations in structure can and do occur in short periods of 2-5 days.

  20. Saturn's dynamic D ring

    USGS Publications Warehouse

    Hedman, M.M.; Burns, J.A.; Showalter, M.R.; Porco, C.C.; Nicholson, P.D.; Bosh, A.S.; Tiscareno, M.S.; Brown, R.H.; Buratti, B.J.; Baines, K.H.; Clark, R.

    2007-01-01

    The Cassini spacecraft has provided the first clear images of the D ring since the Voyager missions. These observations show that the structure of the D ring has undergone significant changes over the last 25 years. The brightest of the three ringlets seen in the Voyager images (named D72), has transformed from a narrow, <40-km wide ringlet to a much broader and more diffuse 250-km wide feature. In addition, its center of light has shifted inwards by over 200 km relative to other features in the D ring. Cassini also finds that the locations of other narrow features in the D ring and the structure of the diffuse material in the D ring differ from those measured by Voyager. Furthermore, Cassini has detected additional ringlets and structures in the D ring that were not observed by Voyager. These include a sheet of material just interior to the inner edge of the C ring that is only observable at phase angles below about 60??. New photometric and spectroscopic data from the ISS (Imaging Science Subsystem) and VIMS (Visual and Infrared Mapping Spectrometer) instruments onboard Cassini show the D ring contains a variety of different particle populations with typical particle sizes ranging from 1 to 100 microns. High-resolution images reveal fine-scale structures in the D ring that appear to be variable in time and/or longitude. Particularly interesting is a remarkably regular, periodic structure with a wavelength of ??? 30 ?? km extending between orbital radii of 73,200 and 74,000 km. A similar structure was previously observed in 1995 during the occultation of the star GSC5249-01240, at which time it had a wavelength of ??? 60 ?? km. We interpret this structure as a periodic vertical corrugation in the D ring produced by differential nodal regression of an initially inclined ring. We speculate that this structure may have formed in response to an impact with a comet or meteoroid in early 1984. ?? 2006 Elsevier Inc. All rights reserved.

  1. Ultrasonic Newton's rings

    SciTech Connect

    Hsu, D.K. ); Dayal, V. )

    1992-03-09

    Interference fringes due to bondline thickness variation were observed in ultrasonic scans of the reflected echo amplitude from the bondline of adhesively joined aluminum skins. To demonstrate that full-field interference patterns are observable in point-by-point ultrasonic scans, an optical setup for Newton's rings was scanned ultrasonically in a water immersion tank. The ultrasonic scan showed distinct Newton's rings whose radii were in excellent agreement with the prediction.

  2. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance

    PubMed Central

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; Junge, Wolfgang; Khan, Shahid

    2015-01-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics that may

  3. Dual-ring scattering method for proton beam spreading

    NASA Astrophysics Data System (ADS)

    Takada, Yoshihisa

    1994-01-01

    A dual-ring double scattering method has been proposed to obtain a large uniform beam field in the proton rotating gantry used for cancer treatment. This method makes it possible to reduce the distance for beam field formation and to use the larger part of the beam. A flat beam field can be formed at a position on the patient by scattering the beam more strongly at the inner part of the dual-ring second scatterer than the outer part.

  4. Bending the Rings

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Saturn's rings appear strangely warped in this view of the rings seen through the upper Saturn atmosphere.

    The atmosphere acts like a lens in refracting (bending) the light reflected from the rings. As the rings pass behind the overexposed limb (edge) of Saturn as seen from Cassini, the ring structure appears to curve downward due to the bending of the light as it passes through the upper atmosphere.

    This image was obtained using a near-infrared filter. The filter samples a wavelength where methane gas does not absorb light, thus making the far-off rings visible through the upper atmosphere.

    By comparing this image to similar ones taken using filters where methane gas does absorb, scientists can estimate the vertical profile of haze and the abundance of methane in Saturn's high atmosphere.

    The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 14, 2005, through a filter sensitive to wavelengths of infrared light centered at 938 nanometers and at a distance of approximately 197,000 kilometers (123,000 miles) from Saturn. The image scale is 820 meters (2,680 feet) per pixel.

  5. Barely Bisected Rings

    NASA Image and Video Library

    2016-09-12

    Saturn's shadow stretched beyond the edge of its rings for many years after Cassini first arrived at Saturn, casting an ever-lengthening shadow that reached its maximum extent at the planet's 2009 equinox. This image captured the moment in 2015 when the shrinking shadow just barely reached across the entire main ring system. The shadow will continue to shrink until the planet's northern summer solstice, at which point it will once again start lengthening across the rings, reaching across them in 2019. Like Earth, Saturn is tilted on its axis. And, just as on Earth, as the sun climbs higher in the sky, shadows get shorter. The projection of the planet's shadow onto the rings shrinks and grows over the course of its 29-year-long orbit, as the angle of the sun changes with respect to Saturn's equator. This view looks toward the sunlit side of the rings from about 11 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft wide-angle camera on Jan. 16, 2015. The view was obtained at a distance of approximately 1.6 million miles (2.5 million kilometers) from Saturn. Image scale is about 90 miles (150 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20498

  6. Motion of a bubble ring in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Cheng, M.; Lou, J.; Lim, T. T.

    2013-06-01

    In this paper, lattice Boltzmann method was undertaken to study the dynamics of a vortex ring bubble (or bubble ring) in a viscous incompressible fluid. The study is motivated partly by our desire to assess whether a bubble ring keeps increasing its radius and decreasing its rise velocity as it rises through fluid as was predicted by Turner ["Buoyant vortex rings," Proc. R. Soc. London, Ser. A 239, 61 (1957)], 10.1098/rspa.1957.0022 and Pedley ["The toroidal bubble," J. Fluid Mech. 32, 97 (1968)], 10.1017/S0022112068000601, or does the ring like a rising bubble, eventually reaches a steady state where its radius and velocity remain constant as was predicted by Joseph et al. [Potential Flows of Viscous and Viscoelastic Fluids (Cambridge University Press, 2008)]. The parameters investigated included ring circulation, Reynolds number, density ratio and Bond number. Our numerical results show that a rising bubble ring increases its radius and decreases its velocity, but the process is interrupted by ring instability that eventually causes it to break up into smaller bubbles. This finding is consistent with the stability analysis by Pedley, who predicted that a bubble ring has a finite lifespan and is ultimately destroyed by surface tension instability. Furthermore, it is found that increasing initial circulation has a stabilizing effect on a bubble ring while increasing Reynolds number or Bond number hastens ring instability, resulting in an earlier break up into smaller bubbles; the number of bubbles depends on the wavenumber of the perturbation.

  7. Propellers in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Sremcevic, M.; Stewart, G. R.; Albers, N.; Esposito, L. W.

    2014-04-01

    Theoretical studies and simulations have demonstrated the effects caused by objects embedded in planetary rings [5, 8]. Even if the objects are too small to be directly observed, each creates a much larger gravitational imprint on the surrounding ring material. These strongly depend on the mass of the object and range from "S" like propeller-shaped structures for about 100m-sized icy bodies to the opening of circumferential gaps as in the case of the embedded moons Pan and Daphnis and their corresponding Encke and Keeler Gaps. Since the beginning of the Cassini mission many of these smaller objects (~ 100m in size) have been identified in Saturn's A ring through their propeller signature in the images [10, 7, 9, 11]. Furthermore, recent Cassini observations indicate the possible existence of objects embedded even in Saturn's B and C ring [6, 2]. In this paper we present our new results about by now classical A ring propellers and more enigmatic B ring population. Due to the presence of self-gravity wakes the analysis of propeller brightness in ISS images always bears some ambiguity [7, 9] and consequently the exact morphology of propellers is not a settled issue. In 2008 we obtained a fortunate Cassini Ultraviolet Imaging Spectrograph (UVIS) occultation of the largest A ring propeller Bleriot. Utilizing Cassini ISS images we obtain Bleriot orbit and demonstrate that UVIS Persei Rev42 occultation did cut across Bleriot about 100km downstream from the center. The occultation itself shows a prominent partial gap and higher density outer flanking wakes, while their orientation is consistent with a downstream cut. While in the UVIS occultation the partial gap is more prominent than the flanking wakes, the features mostly seen in Bleriot images are actually flanking wakes. One of the most interesting aspects of the A ring propellers are their wanderings, or longitudinal deviations from a pure circular orbit [11]. We numerically investigated the possibility of simple moon

  8. Earth Between the Rings of Saturn

    NASA Image and Video Library

    2017-04-20

    This view from NASA's Cassini spacecraft shows planet Earth as a point of light between the icy rings of Saturn. The spacecraft captured the view on April 12, 2017 at 10:41 p.m. PDT (1:41 a.m. EDT). Cassini was 870 million miles (1.4 billion kilometers) away from Earth when the image was taken. Although far too small to be visible in the image, the part of Earth facing toward Cassini at the time was the southern Atlantic Ocean. Earth's moon is also visible to the left of our planet in a cropped, zoomed-in version of the image (Figure 1). The rings visible here are the A ring (at top) with the Keeler and Encke gaps visible, and the F ring (at bottom). During this observation Cassini was looking toward the backlit rings, making a mosaic of multiple images, with the sun blocked by the disk of Saturn. Seen from Saturn, Earth and the other inner solar system planets are all close to the sun, and are easily captured in such images, although these opportunities have been somewhat rare during the mission. The F ring appears especially bright in this viewing geometry. https://photojournal.jpl.nasa.gov/catalog/PIA21445

  9. The Propeller Belts in Saturn A Ring

    NASA Image and Video Library

    2017-01-30

    This image from NASA's Cassini mission shows a region in Saturn's A ring. The level of detail is twice as high as this part of the rings has ever been seen before. The view contains many small, bright blemishes due to cosmic rays and charged particle radiation near the planet. The view shows a section of the A ring known to researchers for hosting belts of propellers -- bright, narrow, propeller-shaped disturbances in the ring produced by the gravity of unseen embedded moonlets. Several small propellers are visible in this view. These are on the order of 10 times smaller than the large, bright propellers whose orbits scientists have routinely tracked (and which are given nicknames for famous aviators). This image is a lightly processed version, with minimal enhancement, preserving all original details present in the image. he image was taken in visible light with the Cassini spacecraft wide-angle camera on Dec. 18, 2016. The view was obtained at a distance of approximately 33,000 miles (54,000 kilometers) from the rings and looks toward the unilluminated side of the rings. Image scale is about a quarter-mile (330 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA21059

  10. Radar Scans of the Saturn Rings

    NASA Astrophysics Data System (ADS)

    West, Richard D.; Janssen, Michael A.; Cuzzi, Jeffrey N.; Anderson, Yanhua; Hamilton, Gary; Cassini Radar Team

    2016-10-01

    The Cassini mission is now heading into its last year of observations. Part of the mission plan includes orbits that bring the spacecraft close to Saturn's rings prior to deorbiting into Saturn's atmosphere. These orbits are providing a unique opportunity to obtain backscatter measurements and relatively high-resolution brightness temperature measurements from the rings. We plan to scan the rings with the radar central beam and obtain backscatter measurements as a function of radial distance with some variation of incidence angle. Active mode radar scans are planned for four of the final high inclination orbits that bring the spacecraft close to the rings. These radar observations will be designed to sweep the A through C rings with varying bandwidth chirps selected to optimize the tradeoff between radial resolution and measurement variance. Pulse compression will deliver radial resolutions varying from about 200 m to around 4 km depending on the bandwidth used. These measurements will provide a 1-D profile of backscatter obtained at 2.2 cm wavelength that will complement similar passive profiles obtained at optical, infrared, and microwave wavelengths. This presentation will summarize the detailed designs and tradeoffs made for these observations. Such measurements will further constrain and inform models of the composition and structure of the ring particle distributions. This work is supported by the NASA Cassini Program at JPL - CalTech.

  11. Grooves and Kinks in the Rings

    NASA Image and Video Library

    2017-06-19

    Many of the features seen in Saturn's rings are shaped by the planet's moons. This view from NASA's Cassini spacecraft shows two different effects of moons that cause waves in the A ring and kinks in a faint ringlet. The view captures the outer edge of the 200-mile-wide (320-kilometer-wide) Encke Gap, in the outer portion of Saturn's A ring. This is the same region features the large propeller called Earhart. Also visible here is one of several kinked and clumpy ringlets found within the gap. Kinks and clumps in the Encke ringlet move about, and even appear and disappear, in part due to the gravitational effects of Pan -- which orbits in the gap and whose gravitational influence holds it open. The A ring, which takes up most of the image on the left side, displays wave features caused by Pan, as well as the moons Pandora and Prometheus, which orbit a bit farther from Saturn on both sides of the planet's F ring. This view was taken in visible light with the Cassini spacecraft narrow-angle camera on March 22, 2017, and looks toward the sunlit side of the rings from about 22 degrees above the ring plane. The view was acquired at a distance of approximately 63,000 miles (101,000 kilometers) from Saturn and at a phase angle (the angle between the sun, the rings and the spacecraft) of 59 degrees. Image scale is 1,979 feet (603 meters) per pixel. https://photojournal.jpl.nasa.gov/catalog/PIA21333

  12. Ring correlations in random networks

    NASA Astrophysics Data System (ADS)

    Sadjadi, Mahdi; Thorpe, M. F.

    2016-12-01

    We examine the correlations between rings in random network glasses in two dimensions as a function of their separation. Initially, we use the topological separation (measured by the number of intervening rings), but this leads to pseudo-long-range correlations due to a lack of topological charge neutrality in the shells surrounding a central ring. This effect is associated with the noncircular nature of the shells. It is, therefore, necessary to use the geometrical distance between ring centers. Hence we find a generalization of the Aboav-Weaire law out to larger distances, with the correlations between rings decaying away when two rings are more than about three rings apart.

  13. Thermodynamic black di-rings

    SciTech Connect

    Iguchi, Hideo; Mishima, Takashi

    2010-10-15

    Previously the five dimensional S{sup 1}-rotating black rings have been superposed in a concentric way by some solitonic methods, and regular systems of two S{sup 1}-rotating black rings were constructed by the authors and then Evslin and Krishnan (we called these solutions 'black di-rings'). In this place we show some characteristics of the solutions of five dimensional black di-rings, especially in thermodynamic equilibrium. After the summary of the di-ring expressions and their physical quantities, first we comment on the equivalence of the two different solution sets of the black di-rings. Then the existence of thermodynamic black di-rings is shown, in which both isothermality and isorotation between the inner black ring and the outer black ring are realized. We also give detailed analysis of peculiar properties of the thermodynamic black di-ring including discussion about a certain kind of thermodynamic stability (instability) of the system.

  14. Piston Ring Pressure Distribution

    NASA Technical Reports Server (NTRS)

    Kuhn, M.

    1943-01-01

    The discovery and introduction of the internal combustion engine has resulted in a very rapid development in machines utilizing the action of a piston. Design has been limited by the internal components of the engine, which has been subjected to ever increasing thermal and mechanical stresses, Of these internal engine components, the piston and piston rings are of particular importance and the momentary position of engine development is not seldom dependent upon the development of both of the components, The piston ring is a well-known component and has been used in its present shape in the steam engine of the last century, Corresponding to its importance, the piston ring has been a rich field for creative activity and it is noteworthy that in spite of this the ring has maintained its shape through the many years. From the many and complicated designs which have been suggested as a packing between piston and cylinder wall hardly one suggestion has remained which does not resemble the original design of cast iron rectangular ring.

  15. Ring solitons on vortices.

    PubMed

    Kevrekidis, P G; Nistazakis, H E; Frantzeskakis, D J; Malomed, B A; Bishop, A R

    2001-12-01

    Interaction of a ring dark or antidark soliton (RDS and RADS, respectively) with a vortex is considered in the defocusing nonlinear Schrödinger equation with cubic (for RDS) or saturable (for RADS) nonlinearities. By means of direct simulations, it is found that the interaction gives rise to either an almost isotropic or a spiral-like pattern. A transition between them occurs at a critical value of the RDS or RADS amplitude, the spiral pattern appearing if the amplitude exceeds the critical value. An initial ring soliton created on top of the vortex splits into a pair of rings moving inward and outward. In the subcritical case, the inbound ring reverses its polarity, bouncing from the vortex core, without conspicuous effect on the core. In the transcritical case, the bounced ring soliton suffers a spiral deformation, while the vortex changes its position and structure and also loses its axial symmetry. Through a variational-type approach to the system's Hamiltonian, we additionally find that the vortex-RDS and vortex-RADS interactions are, respectively, attractive and repulsive. Simulations with the vortex placed eccentrically with respect to the RDS or RADS reveal the generation of strongly localized multispot dark and/or antidark coherent structures. The occurrence of spiral-like patterns in many numerical experiments prompted an attempt to generate a spiral dark soliton, but the latter is found to suffer a core instability that converts it into a rotating dipole emitting waves in the outward direction.

  16. Causes of ring-related leg injuries in birds - evidence and recommendations from four field studies.

    PubMed

    Griesser, Michael; Schneider, Nicole A; Collis, Mary-Anne; Overs, Anthony; Guppy, Michael; Guppy, Sarah; Takeuchi, Naoko; Collins, Pete; Peters, Anne; Hall, Michelle L

    2012-01-01

    One of the main techniques for recognizing individuals in avian field research is marking birds with plastic and metal leg rings. However, in some species individuals may react negatively to rings, causing leg injuries and, in extreme cases, the loss of a foot or limb. Here, we report problems that arise from ringing and illustrate solutions based on field data from Brown Thornbills (Acanthiza pusilla) (2 populations), Siberian Jays (Perisoreus infaustus) and Purple-crowned Fairy-wrens (Malurus coronatus). We encountered three problems caused by plastic rings: inflammations triggered by material accumulating under the ring (Purple-crowned Fairy-wrens), contact inflammations as a consequence of plastic rings touching the foot or tibio-tarsal joint (Brown Thornbills), and toes or the foot getting trapped in partly unwrapped flat-band colour rings (Siberian Jays). Metal rings caused two problems: the edges of aluminium rings bent inwards if mounted on top of each other (Brown Thornbills), and too small a ring size led to inflammation (Purple-crowned Fairy-wrens). We overcame these problems by changing the ringing technique (using different ring types or larger rings), or using different adhesive. Additionally, we developed and tested a novel, simple technique of gluing plastic rings onto metal rings in Brown Thornbills. A review of studies reporting ring injuries (N = 23) showed that small birds (<55 g body weight) are more prone to leg infections while larger birds (>35 g) tend to get rings stuck over their feet. We give methodological advice on how these problems can be avoided, and suggest a ringing hazard index to compare the impact of ringing in terms of injury on different bird species. Finally, to facilitate improvements in ringing techniques, we encourage online deposition of information regarding ringing injuries of birds at a website hosted by the European Union for Bird Ringing (EURING).

  17. Physics of planetary rings

    NASA Astrophysics Data System (ADS)

    Gorkavyi, N.

    2007-08-01

    It is difficult to enumerate all the surprises presented by the planetary rings. The Saturnian rings are stratified into thousands of ringlets and the Uranian rings are compressed into narrow streams, which for some reason or other differ from circular orbits like the wheel of an old bicycle. The edge of the rings is jagged and the rings themselves are pegged down under the gravitational pressure of the satellites, bending like a ship's wake. There are spiral waves, elliptical rings, strange interlacing of narrow ringlets, and to cap it all one has observed in the Neptunian ring system three dense, bright arcs - like bunches of sausages on a transparent string. For celestial mechanics this is a spectacle as unnatural as a bear's tooth in the necklace of the English queen. In the dynamics of planetary rings the physics of collective interaction was supplemented by taking collisions between particles into account. One was led to study a kinetic equation with a rather complex collision integral - because the collisions are inelastic - which later on made it possible, both by using the Chapman-Enskog method and by using the solution of the kinetic equation for a plasma in a magnetic field, to reduce it to a closed set of (hydrodynamical) moment equations [1]. The hydrodynamical instabilities lead to the growth of short-wavelength waves and large-scale structures of the Saturnian rings [1]. We have shown that the formation of the existing dense Uranian rings is connected with the capture of positively drifting ring particles in inner Lindblad resonances which arrest this drift [1]. After the formation of dense rings at the positions of satellite resonances the collective interaction between resonant particles is amplified and the rings can leave the resonance and drift away from the planet and the parent resonance. We can expect in the C ring an appreciable positive ballistic particle drift caused by the erosion of the B ring by micrometeorites. It is therefore natural

  18. Stuck on the Rings

    NASA Image and Video Library

    2014-10-13

    Like a drop of dew hanging on a leaf, Tethys appears to be stuck to the A and F rings from this perspective. Tethys (660 miles, or 1,062 kilometers across), like the ring particles, is composed primarily of ice. The gap in the A ring through which Tethys is visible is the Keeler gap, which is kept clear by the small moon Daphnis (not visible here). This view looks toward the Saturn-facing hemisphere of Tethys. North on Tethys is up and rotated 43 degrees to the right. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 14, 2014. The view was acquired at a distance of approximately 1.1 million miles (1.8 million kilometers) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 22 degrees. Image scale is 7 miles (11 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18284

  19. Deployable Fresnel Rings

    NASA Technical Reports Server (NTRS)

    Kennedy, Timothy F.; Fink, Patrick W.; Chu, Andrew W.; Lin, Gregory Y.

    2014-01-01

    Deployable Fresnel rings (DFRs) significantly enhance the realizable gain of an antenna. This innovation is intended to be used in combination with another antenna element, as the DFR itself acts as a focusing or microwave lens element for a primary antenna. This method is completely passive, and is also completely wireless in that it requires neither a cable, nor a connector from the antenna port of the primary antenna to the DFR. The technology improves upon the previous NASA technology called a Tri-Sector Deployable Array Antenna in at least three critical aspects. In contrast to the previous technology, this innovation requires no connector, cable, or other physical interface to the primary communication radio or sensor device. The achievable improvement in terms of antenna gain is significantly higher than has been achieved with the previous technology. Also, where previous embodiments of the Tri-Sector antenna have been constructed with combinations of conventional (e.g., printed circuit board) and conductive fabric materials, this innovation is realized using only conductive and non-conductive fabric (i.e., "e-textile") materials, with the possible exception of a spring-like deployment ring. Conceptually, a DFR operates by canceling the out-of-phase radiation at a plane by insertion of a conducting ring or rings of a specific size and distance from the source antenna, defined by Fresnel zones. Design of DFRs follow similar procedures to those outlined for conventional Fresnel zone rings. Gain enhancement using a single ring is verified experimentally and through computational simulation. The experimental test setup involves a microstrip patch antenna that is directly behind a single-ring DFR and is radiating towards a second microstrip patch antenna. The first patch antenna and DFR are shown. At 2.42 GHz, the DFR improves the transmit antenna gain by 8.6 dB, as shown in Figure 2, relative to the wireless link without the DFR. A figure illustrates the

  20. Rings dominate western Gulf

    NASA Astrophysics Data System (ADS)

    Vidal L., Francisco V.; Vidal L., Victor M. V.; Molero, José María Pérez

    Surface and deep circulation of the central and western Gulf of Mexico is controlled by interactions of rings of water pinched from the gulf's Loop Current. The discovery was made by Mexican oceanographers who are preparing a full-color, 8-volume oceanographic atlas of the gulf.Anticyclonic warm-core rings pinch off the Loop Current at a rate of about one to two per year, the scientists of the Grupo de Estudios Oceanográficos of the Instituto de Investigaciones Eléctricas (GEO-IIE) found. The rings migrate west until they collide with the continental shelf break of the western gulf, almost always between 22° and 23°N latitude. On their westward travel they transfer angular momentum and vorticity to the surrounding water, generating cyclonic circulations and vortex pairs that completely dominate the entire surface and deep circulation of the central and western gulf.

  1. The Effects of Forming Parameters on Conical Ring Rolling Process

    PubMed Central

    Meng, Wen; Zhao, Guoqun; Guan, Yanjin

    2014-01-01

    The plastic penetration condition and biting-in condition of a radial conical ring rolling process with a closed die structure on the top and bottom of driven roll, simplified as RCRRCDS, were established. The reasonable value range of mandrel feed rate in rolling process was deduced. A coupled thermomechanical 3D FE model of RCRRCDS process was established. The changing laws of equivalent plastic strain (PEEQ) and temperature distributions with rolling time were investigated. The effects of ring's outer radius growth rate and rolls sizes on the uniformities of PEEQ and temperature distributions, average rolling force, and average rolling moment were studied. The results indicate that the PEEQ at the inner layer and outer layer of rolled ring are larger than that at the middle layer of ring; the temperatures at the “obtuse angle zone” of ring's cross-section are higher than those at “acute angle zone”; the temperature at the central part of ring is higher than that at the middle part of ring's outer surfaces. As the ring's outer radius growth rate increases at its reasonable value ranges, the uniformities of PEEQ and temperature distributions increase. Finally, the optimal values of the ring's outer radius growth rate and rolls sizes were obtained. PMID:25202716

  2. Further explorations of cosmogonic shadow effects in the Saturnian rings

    NASA Technical Reports Server (NTRS)

    Alfven, H.; Axnaes, I.; Brenning, N.; Lindqvist, P. A.

    1985-01-01

    The mass distribution in the Saturnian ring system is compared with predictions from the cosmogonic theory of Alfven and Arrhenius (1975) in which matter in the rings was once a magnetized plasma, with gravitation balanced by centrifugal force and by the magnetic field. As the plasma is neutralized, the magnetic force disappears and the matter can be shown to fall in to a distance 2/3 of the original. This supports the cosmogonic shadow effect, also demonstrated for the astroidal belt and in the large scale structure of the Saturnian ring system. The relevance of the comogonic shadow effect for parts of the finer structures of the Saturnian ring system is investigated. It is shown that many structures of the present ring system can be understood as shadows and antishadows of cosmogonic origin. These appear in the form of double rings centered around a position a factor 0.64 (slightly 2/3) closer to Saturn than the causing feature.

  3. Design Considerations for High Energy Electron -- Positron Storage Rings

    DOE R&D Accomplishments Database

    Richter, B.

    1966-11-01

    High energy electron-positron storage rings give a way of making a new attack on the most important problems of elementary particle physics. All of us who have worked in the storage ring field designing, building, or using storage rings know this. The importance of that part of storage ring work concerning tests of quantum electrodynamics and mu meson physics is also generally appreciated by the larger physics community. However, I do not think that most of the physicists working tin the elementary particle physics field realize the importance of the contribution that storage ring experiments can make to our understanding of the strongly interacting particles. I would therefore like to spend the next few minutes discussing the sort of things that one can do with storage rings in the strongly interacting particle field.

  4. Light rings in subarctic conifers as a dendrochronological tool

    SciTech Connect

    Filion, L.; Payette, S.; Gauthier, L.; Boutin, Y.

    1986-01-01

    Light rings are characterized by one or a very few latewood-cell layers, an indication of shortened growing seasons, and are particularly frequent in black spruce (Picea mariana (Mill.) BSP) at the treeline in Quebec. The construction of a light-ring chronology spanning the period AD 1398-1982 showed that the highest frequency (>25%) of light rings among 160 trees and krummholz occurred in 1593, 1620, 1634, 1784, 1816, 1817, 1853, 1969, and 1972. These diagnostic rings may be a useful cross-dating tool for dendroecologists working with living and dead krummholz with a low-growth variability. About two-thirds of the 65 light-ring years coincide with years (or triads) of major volcanic eruptions. The climatic conditions (low temperature) occurring at the end of the growing season, in part induced by the climatic effect of volcanism, seem to initiate light rings.

  5. Saturn's rings - high resolution

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Voyager 2 obtained this high-resolution picture of Saturn's rings Aug. 22, when the spacecraft was 4 million kilometers (2.5 million miles) away. Evident here are the numerous 'spoke' features, in the B-ring; their very sharp, narrow appearance suggests short formation times. Scientists think electromagnetic forces are responsible in some way for these features, but no detailed theory has been worked out. Pictures such as this and analyses of Voyager 2's spoke movies may reveal more clues about the origins of these complex structures. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.

  6. Unidirectional ring lasers

    DOEpatents

    Hohimer, J.P.; Craft, D.C.

    1994-09-20

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity is disclosed. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction. 21 figs.

  7. Unidirectional ring lasers

    DOEpatents

    Hohimer, John P.; Craft, David C.

    1994-01-01

    Unidirectional ring lasers formed by integrating nonreciprocal optical elements into the resonant ring cavity. These optical elements either attenuate light traveling in a nonpreferred direction or amplify light traveling in a preferred direction. In one preferred embodiment the resonant cavity takes the form of a circle with an S-shaped crossover waveguide connected to two points on the interior of the cavity such that light traveling in a nonpreferred direction is diverted from the cavity into the crossover waveguide and reinjected out of the other end of the crossover waveguide into the cavity as light traveling in the preferred direction.

  8. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  9. Satellite Rings Movie

    NASA Image and Video Library

    2000-12-30

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies. The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000. http://photojournal.jpl.nasa.gov/catalog/PIA02872

  10. Ring laser gyroscope anode

    SciTech Connect

    Ljung, B.H.

    1981-03-17

    An anode for a ring laser gyroscope which provides improved current stability in the glow discharge path is disclosed. The anode of this invention permits operation at lower currents thereby allowing a reduction of heat dissipation in the ring laser gyroscope. The anode of one embodiment of this invention is characterized by a thumbtack appearance with a spherical end where the normal sharp end of the thumbtack would be located. The stem of the anode extends from the outside of the gyroscope structure to the interior of the structure such that the spherical end is substantially adjacent to the laser beam.

  11. Motion of a bubble ring in a viscous fluid

    NASA Astrophysics Data System (ADS)

    Lou, Jing; Cheng, Ming; Lim, T. T.; Institute of high Performance Computing, Singapore Team; National University of Singapore Team

    2012-11-01

    A Lattice Boltzmann Method and limited experiments were undertaken to study the dynamic of a vortex ring bubble (or bubble ring) in a viscous incompressible fluid. The study is motivated partly by our desire to assess whether a bubble ring keeps increasing its radius and decreasing its propagation velocity as it rises through fluid was predicted by Turner (1957) and Pedley (1968) or does the ring eventually reach a steady state where its radius and velocity remain constant as was predicted by Joseph et al. (2008). The parameters investigated included ring circulation, Reynolds number, density ratio and Bond number. Our experimental and numerical results show that a rising bubble ring increases its radius and decreases its velocity, but the process is interrupted by ring instability that eventually causes it to break up into smaller bubbles. For the range of flow conditions investigated, there is no evidence that a bubble ring has attained a constant speed and constant radius before breaking up. Furthermore, it is found that increasing initial circulation has a stabilizing effect on a bubble ring while increasing Reynolds number or Bond number hastens ring instability, resulting in an earlier break up into smaller bubbles.

  12. Photometry and polarimetry of Saturn's rings from Pioneer Saturn

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Dilley, J. P.; Fountain, J. W.

    1980-01-01

    A profile of the average normal optical depth for Saturn's rings between 1.22 and 2.35 Saturn radii is examined. In the A and B rings, horizontal inhomogeneities make these values deceptive. A thinner component of the B ring with an optical depth below 0.08 covers up to 4% of its surface area. In the A ring, the more transparent component covers more than 7% of its area and has an optical depth greater than 0.10. These thinner parts of the rings would rarely be apparent from earth based observations. The particles of the C ring are larger than 15 microns and differ from those of the B and A rings. The C ring is either homogeneous with high albedo and forward scattering phase functions, or shows a gradient in albedo with distance from Saturn. Polarimetry of Saturn's ring provides only an upper limit (below 15%) which is consistent with ground-based predictions. Polarization in the outer A ring is negative.

  13. Single ring vs multiple ring determination of Super Kamiokande

    NASA Astrophysics Data System (ADS)

    O'Malley, Patrick; Messier, Mark

    2004-10-01

    Super Kamiokande houses the world's largest Cherenkov detector and whose primary goal is to detect and study neutrino interactions. My purpose in the project was to write a program to enhance the accuracy the ring counting. Currently, ring counting is the largest single source of systematic uncertainty in the single ring event rate, contributing an uncertainty of 5-8This article presents an algorithm the single ring selection efficiency based on a statistical test of azimuthal symmetry of the event topology. With the aid of my advisor, Dr. Mark Messier, I was able to write a program that enhanced the decision between single-ring and multiple ring events by 35

  14. Saturn's Rings, the Yarkovsky Effects, and the Ring of Fire

    NASA Technical Reports Server (NTRS)

    Rubincam, David Parry

    2004-01-01

    The dimensions of Saturn's A and B rings may be determined by the seasonal Yarkovsky effect and the Yarkovsky-Schach effect; the two effects confine the rings between approximately 1.68 and approximately 2.23 Saturn radii, in reasonable agreement with the observed values of 1.525 and 2.267. The C ring may be sparsely populated because its particles are transients on their way to Saturn; the infall may create a luminous Ring of Fire around Saturn's equator. The ring system may be young: in the past heat flow from Saturn's interior much above its present value would not permit rings to exist.

  15. Einstein Ring in Distant Universe

    NASA Astrophysics Data System (ADS)

    2005-06-01

    Using ESO's Very Large Telescope, Rémi Cabanac and his European colleagues have discovered an amazing cosmic mirage, known to scientists as an Einstein Ring. This cosmic mirage, dubbed FOR J0332-3557, is seen towards the southern constellation Fornax (the Furnace), and is remarkable on at least two counts. First, it is a bright, almost complete Einstein ring. Second, it is the farthest ever found. ESO PR Photo 20a/05 ESO PR Photo 20a/05 Deep Image of a Region in Fornax (FORS/VLT) [Preview - JPEG: 400 x 434 pix - 60k] [Normal - JPEG: 800 x 867 pix - 276k] [Full Res - JPEG: 1859 x 2015 pix - 3.8M] ESO PR Photo 20b/05 ESO PR Photo 20b/05 Zoom-in on the Newly Found Einstein Ring (FORS/VLT) [Preview - JPEG: 400 x 575 pix - 168k] [Normal - JPEG: 630 x 906 pix - 880k] Caption: ESO PR Photo 20a/05 is a composite image taken in two bands (B and R) with VLT/FORS1 of a small portion of the sky (field-of-view 7x7' or 1/15th of the area of the full moon). The faintest object seen in the image has a magnitude 26, that is, it is 100 million times fainter than what can be observed with the unaided eye. The bright elliptical galaxy on the lower-left quadrant is a dwarf galaxy part of a large nearby cluster in the Fornax constellation. As for all deep images of the sky, this field shows a variety of objects, the brightest ponctual sources being stars from our Galaxy. By far the field is dominated by thousands of faint background galaxies the colours of which are related to the age of their dominant stellar population, their dust content and their distance. The newly found Einstein ring is visible in the top right part of the image. ESO PR Photo 20b/05 zooms-in on the position of the newly found cosmic mirage. ESO PR Photo 20c/05 ESO PR Photo 20c/05 Einstein Ring in Distant Universe (FORS/VLT) [Preview - JPEG: 400 x 584 pix - 104k] [Normal - JPEG: 800 x 1168 pix - 292k] [Full Res - JPEG: 1502 x 2192 pix - 684k] Caption of ESO PR Photo 20c/05: The left image is magnified and centred

  16. The elusive rings of Neptune

    NASA Astrophysics Data System (ADS)

    Porco, C. C.

    1992-04-01

    An overview of investigations of Neptune's rings is presented in which the recent data and findings from the Voyager 2 mission are emphasized. The evolving interpretation of the ring arcs is outlined, and the concept of resonance in the rings is described. Illustrations of the rings, the moons of Neptune, and the interactions between the two are given, and attention is given to the development of the rings by means of the catastrophic breakup of a planetary satellite. The very large crater on the Mimas satellite is given as evidence of potentially catastrophic impacts, and the implications of further breakup are discussed. A total of four rings are identified which include 3 pronounced rings and one ring that is more diaphanous. Clumps in the arcs are discussed in terms of the possible existence of large objects within the rings, and interparticle collisions are theorized to account for the large arc dust content.

  17. Gravity Signature of the Teague Ring Impact Structure, Western Australia

    NASA Technical Reports Server (NTRS)

    Plescia, J. B.

    1998-01-01

    As part of a multidisciplinary effort to better define the nature of the Teague Ring structure and to understand specifics about the crustal structure, a GPS controlled gravity survey of the feature was undertaken in the austral winter of 1996.

  18. Technology and experiments of 42CrMo bearing ring forming based on casting ring blank

    NASA Astrophysics Data System (ADS)

    Li, Yongtang; Ju, Li; Qi, Huiping; Zhang, Feng; Chen, Guozhen; Wang, Mingli

    2014-03-01

    Bearing ring is the crucial component of bearing. With regard to such problems as material waste, low efficiency and high energy consumption in current process of producing large bearing ring, a new process named "casting-rolling compound forming technology" is researched by taking the typical 42CrMo slew bearing as object. Through theoretical analysis, the design criteria of the main casting-rolling forming parameters are put forward at first. Then the constitutive relationship model of as-cast 42CrMo steel and its mathematical model of dynamic recrystallization are obtained according to the results of the hot compression experiment. By a coupled thermal-mechanical finite element model for radial-axial rolling of bearing ring, the fraction of dynamic recrystallization is calculated and recrystallized grains size are predicated. Meanwhile, the effects of the initial rolling temperature and feed rate of idle roll on material microstructure evolution are analyzed. Finally, the industrial rolling experiment is designed and performed, based on the simulation results. In addition, mechanical and metallographic tests are conducted on rolled bearing ring to get the mechanical parameters and metallographic structure. The experimental data and results show that the mechanical properties of bearing ring produced by casting-rolling compound forming technology are up to industrial standard, and a qualified bearing ring can be successfully formed by employing this new technology. Through the study, a process of forming large bearing ring directly by using casting ring blank is obtained, which could provide an effective theoretical guidance for manufacturing large ring parts. It also has an edge in saving material, lowering energy and improving efficiency.

  19. Chariklo's ring system 1. Structure of the ring system from stellar occultations

    NASA Astrophysics Data System (ADS)

    Berard, Diane; Sicardy, Bruno; Braga-Ribas, Felipe; camargo, julio; Vieira-Martins, Roberto; Assafin, Marcelo; Sickafoose, Amanda A.; Colas, François; Dauvergne, Jean-Luc; Bath, Karl-Ludwig; Maquet, Lucie; Tancredi, Gonzalo; Richichi, Andrea; Puji, Irawati; Ivanov, Valentin; Bradshaw, Jonathan; Broughton, John; Meza, Erick; Ortiz, Jose-Luis; Duffard, Rene; Leiva, Rodrigo

    2016-10-01

    Two dense and narrow rings around Chariklo (the largest centaur object known to date) were discovered by stellar occultation on June 3, 2013 (Braga-Ribas et al., Nature 508, 72, 2014). The main and larger ring is called C1R, while the faintest one is called C2R.Here we report six others occultations by Chariklo's ring system observed on February 16, March 16, April 29, June 28, 2014 and April 26, May 12, 2015. They provide a total of fifteen ring profiles, among which are four resolved profiles of C1R.The latter exhibits a W-shape profile that is essentially opaque at the edges. Its width varies from 4.8 to 7.7 km over the available longitude range. Those caracteristics have been detected in Uranus elliptic rings. The equivalent width We (normal opacity x physical radial width) of C1R is 2 km with typical rms of 1 km, while C2R has We of 0.2 km (rms ~ 0.1 km). None of the rings exhibits variation of We with longitude.Assuming the rings are circular, we can exhibit a pole which is compatible with the two multi-chord ring detections (June 3, 2013 and April 29, 2014): αp=151.4° and δp=41.5°. We will then estimate an upper limit of a possible ring eccentricity based on those two observations.Part of the research leading to these results has received funding from the European Research Council under the European Community's H2020 (2014-2020/ ERC Grant Agreement n 669416 "LUCKY STAR").

  20. Topological Interactions in Multiply Linked DNA Rings

    NASA Astrophysics Data System (ADS)

    Otto, M.; Vilgis, T. A.

    1998-01-01

    The elasticity of DNA catenanes, i.e., multiply linked DNA rings, is investigated using the Gauss invariant as a minimal model for topology conservation. An effective elastic free energy as a function of the distance R between segments located on different rings is obtained. An anharmonic part at large distances, growing as R4, if R>>RG ( RG being the radius of gyration), is found, for R<rings for several linking numbers are in qualitative agreement with distribution functions obtained experimentally from electron micrographs of DNA catenanes [S. D. Levene et al., Biophys. J. 69, 277 (1995)].

  1. Earth Rings for Planetary Environment Control

    NASA Astrophysics Data System (ADS)

    Pearson, Jerome; Oldson, John; Levin, Eugene; Carroll, Joseph

    2002-01-01

    For most of its past, large parts of the Earth have experienced subtropical climates, with high sea levels and no polar icecaps. This warmer environment was punctuated 570, 280, and 3 million years ago with periods of glaciation that covered temperate regions with thick ice for millions of years. At the end of the current ice age, a warmer climate could flood coastal cities, even without human-caused global warming. In addition, asteroids bombard the Earth periodically, with impacts large enough to destroy most life on Earth, and the sun is warming inexorably. This paper proposes a concept to solve these problems simultaneously, by creating an artificial planetary ring about the Earth to shade it. Past proposals for space climate control have depended on gigantic engineering structures launched from Earth and placed in Earth orbit or at the Earth-Sun L1 libration point, requiring fabrication, large launch masses and expense, constant control, and repair. Our solution is to begin by using lunar material, and then mine and remove Earth-orbit-crossing asteroids and discard the tailings into Earth orbit, to form a broad, flat ring like those of Saturn. This solution is evaluated and compared with other alternatives. Such ring systems can persist for thousands of years, and can be maintained by shepherding satellites or by continual replenishment from new asteroids to replace the edges of the ring lost by diffusion. An Earth ring at R = 1.3-1.83 RE would shade only the equatorial regions, moderating climate extremes, and could reverse a century of global warming. It could also absorb particles from the radiation belts, making trips to high Earth orbit and GEO safer for humans and for electronics. It would also light the night many times as bright as the full moon. A preliminary design of the ring is developed, including its location, mass, composition, stability, and timescale required. A one-dimensional climate model is used to evaluate the Earth ring performance

  2. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  3. Exotic damping ring lattices

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.

  4. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  5. Reading, Writing, and Rings!

    ERIC Educational Resources Information Center

    Aschbacher, Pamela; Li, Erika; Hammon, Art

    2008-01-01

    "Reading, Writing, and Rings!" was created by a team of elementary teachers, literacy experts, and scientists in order to integrate science and literacy. These free units bring students inside NASA's Cassini-Huygens mission to Saturn. The authors--a science teacher and education outreach specialist and two evaluators of educational programs--have…

  6. Making Molecular Borromean Rings

    ERIC Educational Resources Information Center

    Pentecost, Cari D.; Tangchaivang, Nichol; Cantrill, Stuart J.; Chichak, Kelly S.; Peters, Andrea J.; Stoddart, Fraser J.

    2007-01-01

    A procedure that requires seven 4-hour blocks of time to allow undergraduate students to prepare the molecular Borromean rings (BRs) on a gram-scale in 90% yield is described. The experiment would serve as a nice capstone project to culminate any comprehensive organic laboratory course and expose students to fundamental concepts, symmetry point…

  7. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  8. Ring of Stellar Death

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This false-color image from NASA's Spitzer Space Telescope shows a dying star (center) surrounded by a cloud of glowing gas and dust. Thanks to Spitzer's dust-piercing infrared eyes, the new image also highlights a never-before-seen feature -- a giant ring of material (red) slightly offset from the cloud's core. This clumpy ring consists of material that was expelled from the aging star.

    The star and its cloud halo constitute a 'planetary nebula' called NGC 246. When a star like our own Sun begins to run out of fuel, its core shrinks and heats up, boiling off the star's outer layers. Leftover material shoots outward, expanding in shells around the star. This ejected material is then bombarded with ultraviolet light from the central star's fiery surface, producing huge, glowing clouds -- planetary nebulas -- that look like giant jellyfish in space.

    In this image, the expelled gases appear green, and the ring of expelled material appears red. Astronomers believe the ring is likely made of hydrogen molecules that were ejected from the star in the form of atoms, then cooled to make hydrogen pairs. The new data will help explain how planetary nebulas take shape, and how they nourish future generations of stars.

    This image composite was taken on Dec. 6, 2003, by Spitzer's infrared array camera, and is composed of images obtained at four wavelengths: 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange) and 8 microns (red).

  9. Crescent Moon with Rings

    NASA Image and Video Library

    2006-04-14

    This poetic scene shows the giant, smog-enshrouded moon Titan behind Saturn nearly edge-on rings. Much smaller Epimetheus 116 kilometers, or 72 miles across is just visible to the left of Titan 5,150 kilometers, or 3,200 miles across

  10. Epimetheus Above the Rings

    NASA Image and Video Library

    2015-11-09

    Although Epimetheus appears to be lurking above the rings here, it's actually just an illusion resulting from the viewing angle. In reality, Epimetheus and the rings both orbit in Saturn's equatorial plane. Inner moons and rings orbit very near the equatorial plane of each of the four giant planets in our solar system, but more distant moons can have orbits wildly out of the equatorial plane. It has been theorized that the highly inclined orbits of the outer, distant moons are remnants of the random directions from which they approached the planets they orbit. This view looks toward the unilluminated side of the rings from about -0.3 degrees below the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 26, 2015. The view was obtained at a distance of approximately 500,000 miles (800,000 kilometers) from Epimetheus and at a Sun-Epimetheus-spacecraft, or phase, angle of 62 degrees. Image scale is 3 miles (5 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18342

  11. Rings In Between

    NASA Image and Video Library

    2011-12-05

    Saturn rings lie between a pair of moons in this view from NASA Cassini spacecraft that features Mimas and Prometheus. Mimas is the more noticeable of the two moons at top left, Prometheus is near the center of image and closest to Cassini.

  12. Ring laser scatterometer

    DOEpatents

    Ackermann, Mark; Diels, Jean-Claude

    2005-06-28

    A scatterometer utilizes the dead zone resulting from lockup caused by scatter from a sample located in the optical path of a ring laser at a location where counter-rotating pulses cross. The frequency of one pulse relative to the other is varied across the lockup dead zone.

  13. Rings from Close Encounters

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  14. Properties of tree rings in LSST sensors

    NASA Astrophysics Data System (ADS)

    Park, H. Y.; Nomerotski, A.; Tsybychev, D.

    2017-05-01

    Images of uniformly illuminated sensors for the Large Synoptic Survey Telescope have circular periodic patterns with an appearance similar to tree rings. These patterns are caused by circularly symmetric variations of the dopant concentration in the monocrystal silicon boule induced by the manufacturing process. Non-uniform charge density results in the parasitic electric field inside the silicon sensor, which may distort shapes of astronomical sources. In this study we analyzed data from fifteen LSST sensors produced by ITL to determine the main parameters of the tree rings: amplitude and period, and also variability across the sensors tested at Brookhaven National Laboratory. Tree ring pattern has a weak dependence on the wavelength. However the ring amplitude gets smaller as wavelength gets longer, since longer wavelengths penetrate deeper into the silicon. Tree ring amplitude gets larger as it gets closer to the outer part of the wafer, from 0.1 to 1.0%, indicating that the resistivity variation is larger for larger radii.

  15. Properties of tree rings in LSST sensors

    DOE PAGES

    Park, H. Y.; Nomerotski, A.; Tsybychev, D.

    2017-05-30

    Images of uniformly illuminated sensors for the Large Synoptic Survey Telescope have circular periodic patterns with an appearance similar to tree rings. Furthermore, these patterns are caused by circularly symmetric variations of the dopant concentration in the monocrystal silicon boule induced by the manufacturing process. Non-uniform charge density results in the parasitic electric field inside the silicon sensor, which may distort shapes of astronomical sources. Here, we analyzed data from fifteen LSST sensors produced by ITL to determine the main parameters of the tree rings: amplitude and period, and also variability across the sensors tested at Brookhaven National Laboratory. Treemore » ring pattern has a weak dependence on the wavelength. But the ring amplitude gets smaller as wavelength gets longer, since longer wavelengths penetrate deeper into the silicon. Tree ring amplitude gets larger as it gets closer to the outer part of the wafer, from 0.1 to 1.0%, indicating that the resistivity variation is larger for larger radii.« less

  16. Neptune Rings and 1989N2

    NASA Image and Video Library

    1996-01-29

    In this image from NASA's Voyager wide-angle taken on Aug. 23 1989, the two main rings of Neptune can be clearly seen. In the lower part of the frame the originally announced ring arc, consisting of three distinct features, is visible. This feature covers about 35 degrees of longitude and has yet to be radially resolved in Voyager images. From higher resolution images it is known that this region contains much more material than the diffuse belts seen elsewhere in its orbit, which seem to encircle the planet. This is consistent with the fact that ground-based observations of stellar occultations by the rings show them to be very broken and clumpy. The more sensitive wide-angle camera is revealing more widely distributed but fainter material. Each of these rings of material lies just outside of the orbit of a newly discovered moon. One of these moons, 1989N2, may be seen in the upper right corner. The moon is streaked by its orbital motion, whereas the stars in the frame are less smeared. The dark area around the bright moon and star are artifacts of the processing required to bring out the faint rings. This wide-angle image was taken from a range of 2 million kilometers (1.2 million miles), through the clear filter. http://photojournal.jpl.nasa.gov/catalog/PIA00053

  17. The gravitational interaction between inclined, elliptical rings. [Uranus rings

    NASA Technical Reports Server (NTRS)

    Yoder, C. F.

    1982-01-01

    An expression for the potential for two elliptical, inclined rings is derived from a model in which the gravitational torque between two wide rings or within a ring of finite width can prevent differential precession caused by planetary oblateness. The model was proposed to explain the observed eccentricity and width variations of the Uranian epsilon ring. The stationary solutions and stability of this system are examined.

  18. The Impact of Climate, Sulfur Dioxide, and Industrial Dust on δ(18)O and δ(13)C in Glucose from Pine Tree Rings Growing in an Industrialized Area in the Southern Part of Poland.

    PubMed

    Sensuła, Barbara M

    The mass spectrometric analysis of the impact of sulfur dioxide and dust emission on carbon and oxygen stable isotopic compositions of glucose hydrolysed from α-cellulose samples extracted from Scots pine growing in the vicinity of "Huta Katowice" steelworks was the main aim of this study. The annual rings covered the time span from 1975 to 2012 AD. The relationships between climatic conditions, sulfur dioxide, and industrial dust emission and oxygen and carbon isotopic compositions were analyzed using correlation function methods. This study shows the first analysis of carbon and oxygen stable isotopes in glucose as the bio-indicators of CO2, sulfur dioxide, and industrial dust emission. The anticoincidence trend of δ(18)O and δ(13)C and dust and sulfur dioxide confirms that the decreases of dust and sulfur dioxide industrial emission increase δ(18)O and δ(13)C values in glucose.

  19. Oscillations at B Ring Edge

    NASA Image and Video Library

    2010-11-01

    This image obtained by NASA Cassini spacecraft of the outer edge of Saturn?s B ring, reveals the combined effects of a tugging moon and oscillations that can naturally occur in disks like Saturn rings and spiral galaxies.

  20. Inorganic glass ceramic slip rings

    NASA Technical Reports Server (NTRS)

    Glossbrenner, E. W.; Cole, S. R.

    1972-01-01

    Prototypes of slip rings have been fabricated from ceramic glass, a material which is highly resistant to deterioration due to high temperature. Slip ring assemblies were not structurally damaged by mechanical tests and performed statisfactorily for 200 hours.

  1. Ring autosomes: some unexpected findings.

    PubMed

    Caba, L; Rusu, C; Plăiaşu; Gug, G; Grămescu, M; Bujoran, C; Ochiană, D; Voloşciuc, M; Popescu, R; Braha, E; Pânzaru, M; Butnariu, L; Sireteanu, A; Covic, M; Gorduza, Ev

    2012-12-01

    Ring chromosomes are rare entities, usually associated with phenotypic abnormalities in correlation with the loss of genetic material. There are various breakpoints and sometimes there is a dynamic mosaicism that is reflected in clinical features. Most of the ring chromosomes are de novo occurrences. Our study reflects the experience of three Romanian cytogenetic laboratories in the field of ring chromosomes. We present six cases with ring chromosomes involving chromosomes 5, 13, 18, and 21. All ring chromosomes were identified after birth in children with plurimalformative syndromes. The ring chromosome was present in mosaic form in three cases, and this feature reflects the ring's instability. In case of ring chromosome 5, we report a possible association with oculo-auriculo-vertebral spectrum.

  2. Planetary rings: Structure and history

    NASA Astrophysics Data System (ADS)

    Esposito, L.

    The composition and structure of planetary rings provide the key evidence to understand their origin and evolution. Before the first space observations, we were able to maintain an idealized view of the rings around Saturn, the only known ring system at that time. Rings were then discovered around Jupiter, Uranus and Neptune. Saturn's F ring was discovered by Pioneer 11. Our ideal view of circular, planar, symmetric and unchanging rings was shattered by observations of inclined, eccentric rings, waves and wavy edges, and numerous processes acting at rates that give timescales much younger than the solar system. Moons within and near the rings sculpt them and are the likely progenitors of future rings. The moonlet lifetimes are much less than Saturn's age. The old idea of ancient rings gave rise to youthful rings, that are recently created by erosion and destruction of small nearby moons. Although this explanation may work well for most rings, Saturn's massive ring system provides a problem. It is extremely improbable that Saturn's rings were recently created by the destruction of a moon as large as Mimas, or even by the breakup of a large comet that passed too close to Saturn. The history of Saturn's rings has been a difficult problem, now made even more challenging by the close-up Cassini measurements. Cassini observations show unexpected ring variability in time and space. Time variations are seen in ring edges, in the thinner D and F rings, and in the neutral oxygen cloud, which outweighs the E ring in the same region around Saturn. The rings are inhomogeneous, with structures on all scales, sharp gradients and edges. Compositional gradients are sharper than expected, but nonetheless cross structural boundaries. This is evidence for ballistic transport that has not gone to completion. The autocovariance maximizes in the middle of the A ring, with smaller structure near the main rings' outer edge. Density wave locations have a fresher ice composition. The

  3. Climatic response of annual tree-rings

    NASA Astrophysics Data System (ADS)

    Ageev, Boris G.; Gruzdev, Aleksandr N.; Ponomarev, Yurii N.; Sapozhnikova, Valeria A.

    2014-11-01

    Extensive literature devoted to investigations into the influence of environmental conditions on the plant respiration and respiration rate. It is generally accepted that the respired CO2 generated in a stem completely diffuses into the atmosphere. Results obtained from explorations into the CO2 content in disc tree rings by the method proposed in this work shows that a major part of CO2 remains in tree stems and exhibits inter-annual variability. Different methods are used to describe of CO2 and H2O distributions in disc tree rings. The relation of CO2 and H2O variations in a Siberian stone pine disc to meteorological parameters are analyzed with use of wavelet, spectral and cross-spectral techniques. According to a multiple linear regression model, the time evolution of the width of Siberian stone pine rings can be partly explained by a combined influence of air temperature, precipitation, cloudiness and solar activity. Conclusions are made regarding the response of the CO2 and H2O content in coniferous tree disc rings to various climatic factors. Suggested method of CO2, (CO2+H2O) detection can be used for studying of a stem respiration in ecological risk areas.

  4. RINGED ACCRETION DISKS: EQUILIBRIUM CONFIGURATIONS

    SciTech Connect

    Pugliese, D.; Stuchlík, Z. E-mail: zdenek.stuchlik@physics.cz

    2015-12-15

    We investigate a model of a ringed accretion disk, made up by several rings rotating around a supermassive Kerr black hole attractor. Each toroid of the ringed disk is governed by the general relativity hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. Properties of the tori can then be determined by an appropriately defined effective potential reflecting the background Kerr geometry and the centrifugal effects. The ringed disks could be created in various regimes during the evolution of matter configurations around supermassive black holes. Therefore, both corotating and counterrotating rings have to be considered as being a constituent of the ringed disk. We provide constraints on the model parameters for the existence and stability of various ringed configurations and discuss occurrence of accretion onto the Kerr black hole and possible launching of jets from the ringed disk. We demonstrate that various ringed disks can be characterized by a maximum number of rings. We present also a perturbation analysis based on evolution of the oscillating components of the ringed disk. The dynamics of the unstable phases of the ringed disk evolution seems to be promising in relation to high-energy phenomena demonstrated in active galactic nuclei.

  5. Uranus Rings and Two Moons

    NASA Image and Video Library

    1999-06-19

    Voyager 2 has discovered two hepherd satellites associated with the rings of Uranus. The two moons, designated 1986U7 and 1986U8, are seen here on either side of the bright epsilon ring; all nine of the known Uranian rings are visible.

  6. Uranus: the rings are black.

    PubMed

    Sinton, W M

    1977-11-04

    An upper limit of 0.05 is established for the geometric albedo of the newly discovered rings of Uranus. In view of this very low albedo, the particles of the rings cannot be ice-covered as are those of rings A and B of Saturn.

  7. Ring closure in actin polymers

    NASA Astrophysics Data System (ADS)

    Sinha, Supurna; Chattopadhyay, Sebanti

    2017-03-01

    We present an analysis for the ring closure probability of semiflexible polymers within the pure bend Worm Like Chain (WLC) model. The ring closure probability predicted from our analysis can be tested against fluorescent actin cyclization experiments. We also discuss the effect of ring closure on bend angle fluctuations in actin polymers.

  8. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  9. DC-Powered Jumping Ring

    ERIC Educational Resources Information Center

    Jeffery, Rondo N.; Farhang, Amiri

    2016-01-01

    The classroom jumping ring demonstration is nearly always performed using alternating current (AC), in which the ring jumps or flies off the extended iron core when the switch is closed. The ring jumps higher when cooled with liquid nitrogen (LN2). We have performed experiments using DC to power the solenoid and find similarities and significant…

  10. Investigations of planetary ring phenomena

    NASA Technical Reports Server (NTRS)

    Burns, Joseph A.

    1987-01-01

    Faint planetary rings, their dynamical behavior and physical properties, were the main focus of the research efforts. The motion of weakly-charged dust through the gravitational and magnetic fields of Jupiter were examined. Several topics concerning features of Saturn's rings were addressed. The origin and fate of the Uranian ring dust is presently being studied.

  11. The Case for Massive and Ancient Rings of Saturn

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2016-10-01

    Analysis of Voyager and Pioneer 11 results give a mass for Saturn's rings, M = 5 x 10-8 Msat. This is about the mass of Saturn's small moon Mimas. This has been interpreted as a lower limit to the ring mass (Esposito et al 1983), since the thickest parts of the rings were not penetrated by the stellar occultstion, and this calculation assumes an unvarying particle size throughout the rings. Because the rings are constantly bombarded by micrometeroids, their current composition of nearly pure water ice implies such low mass rings must have formed recently. The case is particularly strong for Saturn's A ring, where the data are the best, implying the A ring is less than 10% of the age of the Saturn (Esposito 1986). Cassini results compound this problem. UVIS spectra are consistent with either young rings or rings about 10x as massive as the Voyager estimate (Elliott and Esposito (2011). CDA confirms the impacting mass flux is similar to that assumed for the pollution calculations (Kempf etal 2015). VIMS analysis of density wave signatures in the B ring gives a value of about 1/3 the Voyager value (Hedmann etal 2016). This VIMS result implies the rings are even younger! The problem is that young rings are very unlikely to be formed recently, meaning that we live in a very special epoch, following some unlikely recent origin… like disruption of a medium sized moon or capture of the fragments of a disrupted comet (Charnoz etal 2009).To take the VIMS results at face value, Saturn's low mass rings must be very young. The optically thick B ring must be made of small, porous or fractal particles. An alternative is that we accept the higher mass interpretation of the Pioneer 11 results (Esposito etal 2008) using the granola bar model of Colwell etal 2007. This would imply that the density wave structure seen by VIMS is not sensing all the mass in the rings, where structure near strong resonances is dominted by temporary aggregates, and where non-linear effects cause the

  12. Mimas Against the Rings

    NASA Image and Video Library

    2005-08-05

    During its close flyby of Saturn's moon Mimas on Aug. 2, 2005, Cassini caught a glimpse of Mimas against the broad expanse of Saturn's rings. The Keeler Gap in the outer A ring, in which Cassini spied a never-before-seen small moon (see PIA06237), is at the upper right. The ancient, almost asteroid-like surface of Mimas is evident in its crater-upon-crater appearance. Even the material which has slumped down into the bottom of some of its craters bears the marks of later impacts. This image was taken through the clear filter of the Cassini spacecraft narrow-angle camera at a distance of 68,000 kilometers (42,500 miles) from Mimas and very near closest approach. The smallest features seen on the moon are about 400 meters wide (440 yards); the Sun-Mimas-Cassini angle is 44 degrees. http://photojournal.jpl.nasa.gov/catalog/PIA06412

  13. Saturn Ring Observer

    NASA Technical Reports Server (NTRS)

    Spilker, T. R.

    2001-01-01

    Answering fundamental questions about ring particle characteristics, and individual and group behavior, appears to require close-proximity (a few km) observations. Saturn's magnificent example of a ring system offers a full range of particle sizes, densities, and behaviors for study, so it is a natural choice for such detailed investigation. Missions implementing these observations require post-approach Delta(V) of approximately 10 km/s or more, so past mission concepts called upon Nuclear Electric Propulsion. The concept described here reduces the propulsive Delta(V) requirement to as little as 3.5 km/s, difficult but not impossible for high-performance chemical propulsion systems. Additional information is contained in the original extended abstract.

  14. Satellite Rings Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies.

    The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000.

    Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C.

  15. Satellite Rings Movie

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This brief movie clip (of which the release image is a still frame), taken by NASA's Cassini spacecraft as it approached Jupiter, shows the motions, over a 16 hour-period, of two satellites embedded in Jupiter's ring. The moon Adrastea is the fainter of the two, and Metis the brighter. Images such as these will be used to refine the orbits of the two bodies.

    The movie was made from images taken during a 40-hour sequence of the Jovian ring on December 11, 2000.

    Cassini is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages Cassini for NASA's Office of Space Science, Washington, D.C.

  16. The Secular Evolution of a Close Ring-Satellite System

    NASA Astrophysics Data System (ADS)

    Hahn, Joseph M.

    2007-10-01

    Current literature on ring-satellite interactions tells us that the long-term orbital stability of a satellite that orbits near a planetary ring is uncertain. This is because the satellite's perturbations at its Lindblad and corotation resonances in the ring tend to alter the satellite's eccentricity e, but it is unclear whether e-damping or e-excitation is the result, since that depends on whether particle motions at the corotation resonances are unsaturated (Goldreich & Tremaine 1982). Further, the stability of the satellite's inclination I seems grim, since the satellite's inclination is excited by its many vertical resonances in the ring (Borderies et al 1984). Consequently, it is unclear whether the small gap-embedded satellites Pan (which inhabits the Encke gap in Saturn's A ring) and Daphnis (which inhabits the Keeler gap) should in fact reside in nearly circular orbits that are coplanar with the ring. To address this uncertainty, the following considers the satellite's secular gravitational perturbations of the ring, which can also alter the satellite's e and I. The Lagrange planetary equations are used to show that a small gap-embedded satellite can launch spiral density and spiral bending waves that propagate radially outwards from the gap's outer edge. These one-armed waves propagate via the secular part of the ring's self-attraction, and they tend to have low amplitudes and long wavelengths, 100's of km in Saturn's A ring. The excitation of these waves also damps the satellite's e and I at rates that depend on the satellite's mass, ring surface density, the gap width, and the planet's oblateness (Hahn 2007). These analytic predictions are also confirmed using the `rings-model' of Hahn (2003) to simulate a ring-satellite system. Whether this secular interaction can stabilize a satellite's e and I will be determined, and whether these low-amplitude waves have any observational consequences will also be discussed.

  17. Strained Ring Energetic Binders

    DTIC Science & Technology

    1993-08-27

    polyhomobenzvalene ( PHBV ). PHBV was not found to have the mechanical instability problems of PBV, but was still thermally unstable (Tonset - 660C, Tmax - 1090C...DISCUSSION 4 Polybenzvalene (PBV) 4 Polyhomobenzvalene ( PHBV ) 6 Chain-Transfer Studies 11 CONCLUSIONS 15 EXPERIMENTAL PROCEDURES 16 .F 4E 19 APPENDICES A...strained ring polymers similar to PBV are known. The investigation of one of these polymers, polyhomobenzvalene ( PHBV ), is also described in this report

  18. Accurate localization of organ representation areas on the feet & hands using the bi-digital O-ring test resonance phenomenon: its clinical implication in diagnosis & treatment--Part I.

    PubMed

    Omura, Y

    1994-01-01

    Accuracy of the widely used organ representation areas, currently used in different schools of foot and hand reflexology was evaluated using Bi-Digital O-Ring test resonance phenomenon. Our previous study indicated that mapping organ representation areas of the tongue using Bi-Digital O-Ring Test resonance phenomenon between 2 identical substances often provided more reliable clinical information for both diagnosis and treatment than the 2 widely used, but crude, traditional schools of Chinese tongue diagnosis. This same method was applied for the mapping of the organ representation areas on the feet and hands. We succeeded in mapping the following areas on human feet: 1) Middle (3rd) toe on the sole side represents the following starting from the tip: A) Head, B) Face with eye, ear, nose, and mouth (1st Digit) C) Neck and organs within the neck (narrow band of space between 1st crease after the 1st digit and crease at the junction of the beginning of the sole); 2) 2nd and 4th toe represent upper extremities, the beginning tip being fingers and hands. The crease at the base of these toes represents the shoulder. The 2nd toe represents right upper extremity, and the 4th toe represents left upper extremity; 3) 1st and 5th toes in both the right and left feet represent lower extremities with the tip being the toes and soles of feet. The crease at the base of these toes represents the inguinal area. The 1st toe of each foot represents right lower extremity, and 5th toe represents left lower extremity. The sole of the foot is divided into the following 3 distinctive sections. 1) Upper (1st) section represents organs in the chest cavity including 2 thymus glands, trachea, 2 lungs, with the heart between them, and with the esophagus appearing as a narrow band outside of the lung near and below the 1st and 2nd toe depending upon the individual. Chest section occupies the first 1/3 to 1/5 (on a relatively long foot) of the entire sole. The boundary between the chest and G

  19. Which Ringed Planet...!?

    NASA Astrophysics Data System (ADS)

    2002-12-01

    Don't worry - you are not the only one who thought this was a nice amateur photo of planet Saturn, Lord of the Rings in our Solar System! But then the relative brightness and positions of the moons may appear somewhat unfamiliar... and the ring system does look unusually bright when compared to the planetary disk...?? Well, it is not Saturn, but Uranus , the next giant planet further out, located at a distance of about 3,000 million km, or 20 times the distance between the Sun and the Earth. The photo shows Uranus surrounded by its rings and some of the moons, as they appear on a near-infrared image that was obtained in the K s -band (at wavelength 2.2 µm) with the ISAAC multi-mode instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile) . The exposure was made on November 19, 2002 (03:00 hrs UT) during a planetary research programme. The observing conditions were excellent (seeing 0.5 arcsec) and the exposure lasted 5 min. The angular diameter of Uranus is about 3.5 arcsec. The observers at ISAAC were Emmanuel Lellouch and Thérése Encrenaz of the Observatoire de Paris (France) and Jean-Gabriel Cuby and Andreas Jaunsen (both ESO-Chile). The rings The rings of Uranus were discovered in 1977, from observations during a stellar occultation event by astronomer teams at the Kuiper Airborne Observatory (KAO) and the Perth Observatory (Australia). Just before and after the planet moved in front of the (occulted) star, the surrounding rings caused the starlight to dim for short intervals of time. Photos obtained from the Voyager-2 spacecraft in 1986 showed a multitude of very tenuous rings. These rings are almost undetectable from the Earth in visible light. However, on the present VLT near-infrared picture, the contrast between the rings and the planet is strongly enhanced. At the particular wavelength at which this observation was made, the infalling sunlight is almost completely absorbed by gaseous methane present in the planetary atmosphere

  20. Precooler Ring Vacuum System

    SciTech Connect

    Moenich, J.

    1980-10-02

    The precooler vacuum system, as proposed by FNAL, is based on a suitable modification of the existing Electron Cooling Ring System. Because of the magnetic cycle of the bending magnets, distributed ion pumping, as exists in the Electron Cooling Ring, is not applicable. Instead, the proposed pumping will be done with commercial appendage ion pumps mounted approximately every two meters around the circumference of the ring. The loss of effective pumping speed and non-uniformity of system pressure with appendage pumps may not be major considerations but the large number required does effect experimental and analytical equipment placement considerations. There is a distributed pumping technique available which: (1) is not affected by the magnetic cycle of the bending magnets; (2) will provide a minimum of four times the hydrogen pumping speed of the proposed appendage ion pumps; (3) will require no power during pumping after the strip is activated; (4) will provide the heat source for bakeout; (5) is easily replaceable; and (6) can be purchased, installed, and operated at a generous economic advantage over the presently proposed ion pumped system. The pumping technique referred to is non-evaporable gettering with ST101 Zr/Al pumping strip. A technical description of this pumping strip is given on Data Sheet 1 and 2 attached to this report.

  1. Swarming rings of bacteria.

    NASA Astrophysics Data System (ADS)

    Brenner, M. P.; Levitov, L. S.

    1996-03-01

    The behavior of bacterii controlled by chemotaxis can lead to a complicated spatial organization, producing swarming rings, and steady or moving aggregates( E. O. Budrene, and H. C. Berg, Complex patterns formed by motile cells of Escherichia coli. Nature 349, 630-633 (1991). ). We present a simple theory that explains the experimentally observed structures, by solving analytically two coupled differential equations, for the densities of bacterii and of chemoattractant. The equations have an interesting relation to the exactly solvable Burgers equation, and admit soliton-like solutions, that can be steady or moving. In addition, we find that there are singular solutions to the equations in which the bacterial density diverges. The theory agrees very well with the experiment: the solitons correspond to the observed travelling rings, the singularities describe formation of aggregates. In particular, the theory explains why the velocity of swarming rings decreases with the increase of the food concentration, the fact apparently not accounted by other existing approaches( L. Tsimring et. al., Phys. Rev. Lett., 75, 1859 (1995); Woodward, et al, Biophysical Journal, 68, 2181-2189 (1995). ).

  2. Saturn's ``Gossamer'' Ring: The F Ring's Inner Sheet

    NASA Astrophysics Data System (ADS)

    Showalter, M. R.; Burns, J. A.; Hamilton, D. P.

    1998-09-01

    Recent Galileo and Earth-based images have revealed for the first time that Jupiter's ``gossamer'' ring is actually composed of two rings, one bounded at the outer edge by Amalthea and the other bounded by Thebe. Dynamical models suggest that these rings are composed of dust grains ejected off the surfaces of the two moons, which then evolve inward under Poynting-Robertson drag. A very faint sheet of material filling the region between Saturn's A and F Rings reported by Burns et al. (BAAS 15, 1013--1014, 1983) may be a dynamically analogous system, in which dust escapes from the F Ring and evolves inward to the A Ring. Unlike Jupiter's gossamer rings, however, the inner sheet of Saturn's F Ring has been well observed from a large range of phase angles and visual wavelengths by Voyager. Voyager images reveal that this faint ring shows a tenfold increase in brightness between phase angles of 125(deg) and 165(deg) , indicating that it is composed of fine dust microns in size. Preliminary estimates of the normal optical depth fall in the range 1--2*E(-4) , depending on the dust size distribution assumed. Initial spectrophotometry reveals that the ring is neutral in color. The ring is uniform in brightness over the entire region between the two rings, with no evidence for internal structure associated with Prometheus and Atlas, suggesting that neither of these embedded moons acts as either a source or a sink. We will refine the aforementioned measurements and develop photometric models to better constrain the properties of the dust in this ring. This will enable us to relate the dust population to that in the F Ring proper, and to better explore the dynamical processes at work.

  3. Persistent organic pollutants in ringed seals from the Russian Arctic.

    PubMed

    Savinov, Vladimir; Muir, Derek C G; Svetochev, Vladislav; Svetocheva, Olga; Belikov, Stanislav; Boltunov, Andrey; Alekseeva, Ludmila; Reiersen, Lars-Otto; Savinova, Tatiana

    2011-06-15

    Organochlorine compounds total DDT (ΣDDT), total HCH isomers (ΣHCH), toxaphenes (sum of Parlar 26, 50, 62), mirex, endrin, methoxychlor, total chlorinated benzenes (ΣCBz), total chlordane compounds (ΣCHL), polychlorinated biphenyls (total of 56 congeners; ΣPCBs), polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), and polybrominated diphenyl ethers (sum of 7 tri- to hepta congeners; ΣPBDEs) were analysed in the blubber of adult ringed seals from the four areas of the Russian Arctic (White Sea, Barents Sea, Kara Sea and Chukchi Sea) collected in 2001-2005. Ringed seals from the south-western part of the Kara Sea (Dikson Island - Yenisei estuary) were the most contaminated with ΣDDTs, ΣPCBs, ΣCHL, and mirex as compared with those found in the other three areas of Russian Arctic, while the highest mean concentrations of ΣHCHs and PCDD/Fs were found in the blubber of ringed seals from the Chukchi Sea and the White Sea, respectively. Among all organochlorine compounds measured in ringed seals from the European part of the Russian Arctic, concentrations of ΣDDT and ΣPCBs only were higher as compared with the other Arctic regions. Levels of all other organochlorine compounds were similar or lower than in seals from Svalbard, Alaska, the Canadian Arctic and Greenland. ΣPBDEs were found in all ringed seal samples analysed. There were no significant differences between ΣPBDE concentrations found in the blubber of ringed seals from the three studied areas of the European part of the Russian Arctic, while PBDE contamination level in ringed seals from the Chukchi Sea was 30-50 times lower. ΣPBDE levels in the blubber of seals from the European part of the Russian Arctic are slightly higher than in ringed seals from the Canadian Arctic, Alaska, and western Greenland but lower compared to ringed seals from Svalbard and eastern Greenland.

  4. Helmet latching and attaching ring

    NASA Technical Reports Server (NTRS)

    Chase, E. W.; Viikinsalo, S. J. (Inventor)

    1970-01-01

    A neck ring releasably secured to a pressurized garment carries an open-ended ring normally in the engagement position fitted into an annular groove and adapted to fit into a complementary annular groove formed in a helmet. Camming means formed on the inner surface at the end of the helmet engages the open-ended ring to retract the same and allow for one motion donning even when the garment is pressurized. A projection on the end of the split ring is engageable to physically retract the split ring.

  5. Planetary ring dynamics and morphology

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Durisen, Richard H.; Shu, Frank H.

    1987-01-01

    Evidence for a moonlet belt in the region between Saturn's close-in moonrings Pandora and Prometheus is discussed. It is argued that little-known observations of magnetospheric electron density by Pioneer 11 imply substantial, ongoing injections of mass into the 2000 km region which surrounds the F ring. A hypothesis is presented that these events result naturally from interparticle collisions between the smaller members of an optically thin belt of moonlets. Also discussed is work on Uranus ring structure and photometry, image processing and analysis of the Jonian ring strucure, photometric and structural studies of the A ring of Saturn, and improvements to an image processing system for ring studies.

  6. Cassini UVIS Observations Show Active Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Esposito, L.; Colwell, J. E.; UVIS Team

    2004-12-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) is part of the remote sensing payload of the NASA/ESA Cassini spacecraft. This spectrograph includes channels for extreme UV and far UV spectroscopic imaging, high speed photometry of stellar occultations, solar EUV occultation, and a hydrogen/deuterium absorption cell. We report our initial results from UVIS observations of Saturn's rings. Dynamic interactions between neutrals, ions, rings, moons and meteoroids produce a highly structured and time variable Saturn system Oxygen in the Saturn system dominates the magnetosphere. Observed fluctuations indicate close interactions with plasma sources. Stochastic events in the E ring may be the ultimate source. The spectral signature of water ice is seen on Phoebe and in Saturn's rings. Water ice is mixed non-uniformly with darker constituents. The high structure of the UV ring reflectance argues that collisional transport dominates ballistic transport in darkening the rings. Our preliminary results support the idea that rings are recycled fragments of moons: the current processes are more important than history and initial conditions. The spectra along the UVIS SOI radial scan indicate varying amounts of water ice. In the A ring, the ice fraction increases outward to a maximum at the outer edge. This large-scale variation is consistent with initially pure ice that has suffered meteoritic bombardment over the age of the Solar system (Cuzzi and Estrada 1998). We also see variations over scales of 1000 - 3000 km, which cannot be explained by this mechanism. Ballistic transport of spectrally neutral extrinsic pollutants from meteoroids striking the rings has a typical throw distance of 6000 km (Durisen et al 1989), too long to explain this finer structure. We propose a class of smaller renewal events, in which a small moon residing within the rings is shattered by an external impactor (Colwell and Esposito 1993, Barbara and Esposito 2002, Esposito and Colwell 2003). The

  7. Ring Autosomes: Some Unexpected Findings

    PubMed Central

    Caba, L; Rusu, C; Plăiaşu; Gug, G; Grămescu, M; Bujoran, C; Ochiană, D; Voloşciuc, M; Popescu, R; Braha, E; Pânzaru, M; Butnariu, L; Sireteanu, A; Covic, M; Gorduza, EV

    2012-01-01

    Ring chromosomes are rare entities, usually associated with phenotypic abnormalities in correlation with the loss of genetic material. There are various breakpoints and sometimes there is a dynamic mosaicism that is reflected in clinical features. Most of the ring chromosomes are de novo occurrences. Our study reflects the experience of three Romanian cytogenetic laboratories in the field of ring chromosomes. We present six cases with ring chromosomes involving chromosomes 5, 13, 18, and 21. All ring chromosomes were identified after birth in children with plurimalformative syndromes. The ring chromosome was present in mosaic form in three cases, and this feature reflects the ring’s instability. In case of ring chromosome 5, we report a possible association with oculo-auriculo-vertebral spectrum. PMID:24052730

  8. Mass of Saturn's A ring

    NASA Technical Reports Server (NTRS)

    Horn, L. J.; Russell, C. T.

    1993-01-01

    The mass of Saturn's A ring is reestimated using the behavior of spiral density waves embedded in the ring. The Voyager photopolarimeter (PPS) observed the star delta-Scorpii as it was occulted by Saturn's rings during the Voyager 2 flyby of Saturn in 1981 producing a radial profile of the rings. We examined forty spiral density waves in the Voyager PPS data of the A ring including 10 weaker waves that have not been previously analyzed by means of an autoregressive power spectral technique called Burg. The strengths of this new method for ring studies are that weaker, less extended waves are easily detected and characterized. This method is also the first one which does not require precise knowledge of the resonance location and phase of the wave in order to calculate the surface mass density. Uncertainties of up to 3 km are present in the currently available radial scales for Saturn's rings.

  9. A season in Saturn's rings: Cycling, recycling and ring history

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Meinke, B. K.; Albers, N.; Sremcevic, M.

    2012-04-01

    Cassini experiments have watched Saturn's ring system evolve before our eyes. Images and occultations show changes and transient events. The rings are a dynamic and complex geophysical system, incompletely modeled as a single-phase fluid. Key Cassini observations: High resolution images show straw, propellers, embedded moonlets, and F ring objects. Multiple UVIS, RSS and VIMS occutlations indicate multimodal ringlet and edge structure, including free and forced modes along with stochastic perturbations that are most likely caused by nearby mass concentrations. Vertical excursions are evident at ring edges and in other perturbed regions. The rings are occasionally hit by meteorites that leave a signature that may last centuries; meteoritic dust pollutes the rings. Temperature, reflectance and transmission spectra are influenced by the dynamical state of the ring particles. Saturn's Equinox 2009: Oblique lighting exposed vertical structure and embedded objects. The rings were the coldest ever. Images inspired new occultation and spectral analysis that show abundant structure in the perturbed regions. The rings are more variable and complex than we had expected prior to this seasonal viewing geometry. Sub-kilometer structure in power spectral analysis: Wavelet analysis shows features in the strongest density waves and at the shepherded outer edge of the B ring. Edges are variable as shown by multiple occultations and occultations of double stars. F ring kittens: 25 features seen in the first 102 occultations show a weak correlation with Prometheus location. We interpret these features as temporary aggregations. Simulation results indicate that accretion must be enhanced to match the kittens' size distribution. Images show that Prometheus triggers the formation of transient objects. Propellers and ghosts: Occulations and images provide evidence for small moonlets in the A, B and C rings. These indicate accretion occurs inside the classical Roche limit. Implications

  10. Erratum: Voyager Color Photometry of Saturn's Main Rings

    NASA Technical Reports Server (NTRS)

    Estrada, Paul R.; Cuzzi, Jeffrey N.; Showalter, Mark R.; DeVincenzi, Donald (Technical Monitor)

    2002-01-01

    We correct a calibration error in our earlier analysis of Voyager color observations of Saturn's main rings at 14 deg phase angle and present thoroughly revised and reanalyzed radial profiles of the brightness of the main rings in Voyager G, V, and UV filters, and ratios of these brightnesses. These results are consistent with more recent HST results at 6 deg phase angle, once allowance is made for plausible phase reddening of the rings. Unfortunately, the Voyager camera calibration factors are simply not sufficiently well known for a combination of the Voyager and HST data to be used to constrain the phase reddening quantitatively. However, some interesting radial variations in reddening between 6-14 deg phase angles are hinted at. We update a ring-and-satellite color vs. albedo plot from Cuzzi and Estrada in several ways. The A and B rings are still found to be in a significantly redder part of color-albedo space than Saturn's icy satellites.

  11. New Views of Jupiter's Rings

    NASA Astrophysics Data System (ADS)

    Burns, J. A.

    1998-09-01

    Jupiter's rings are the archetype of ethereal planetary rings (very-low optical-depth bands containing micron-sized "dust"). As a result of much improved observations by Galileo (Ockert-Bell* -- most citations are et al. and Icarus in press* or this meeting) and Keck (de Pater*), we now understand the nature of such rings. The ring has three components: a 104 km-thick toroidal halo (1.4-1.7 RJ; normal optical depth t = 10-6), a thin main ring (1.7-1.8 RJ; t = 10-6), and a pair of exterior gossamer rings (1.8-3.5RJ; t = 10-7). The main ring has patchy ( 20-30 percent) brightness. The ring is reddish and its particles satisfy a -2.5 differential power-law size distribution. Because particle lifetimes are brief, the rings must be continually regenerated, by collisions into parent bodies, which may be unseen or may be the known small ring-moons (Thomas*, Simonelli). The gossamer ring seems to be collisional ejecta derived from the ring-moons Amalthea and Thebe, and evolving inward by Poynting-Robertson drag (Burns). The particles drift through many electromagnetic resonances, clustering around synchronous orbit, which produce jumps in the particles' inclinations (Hamilton). The main ring is probably debris from Adrastea and Metis, which orbit in the equatorial plane. The halo particles are driven vertically by electromagnetic forces, which may be resonant (Schaffer & Burns) or not (Horanyi & Cravens). When halo orbits become highly distorted, particles are lost into Jupiter. Similar faint rings may be attendant to all small, close-in satellites (Showalter).

  12. Aromatic and antiaromatic ring currents in a molecular nanoring

    NASA Astrophysics Data System (ADS)

    Peeks, Martin D.; Claridge, Timothy D. W.; Anderson, Harry L.

    2016-12-01

    Aromatic and antiaromatic molecules—which have delocalized circuits of [4n + 2] or [4n] electrons, respectively—exhibit ring currents around their perimeters. The direction of the ring current in an aromatic molecule is such as to generate a magnetic field that opposes the external field inside the ring (a ‘diatropic’ current), while the ring current in an antiaromatic molecule flows in the reverse direction (‘paratropic’). Similar persistent currents occur in metal or semiconductor rings, when the phase coherence of the electronic wavefunction is preserved around the ring. Persistent currents in non-molecular rings switch direction as a function of the magnetic flux passing through the ring, so that they can be changed from diatropic (‘aromatic’) to paratropic (‘antiaromatic’) simply by changing the external magnetic field. As in molecular systems, the direction of the persistent current also depends on the number of electrons. The relationship between ring currents in molecular and non-molecular rings is poorly understood, partly because they are studied in different size regimes: the largest aromatic molecules have diameters of about one nanometre, whereas persistent currents are observed in microfabricated rings with diameters of 20-1,000 nanometres. Understanding the connection between aromaticity and quantum-coherence effects in mesoscopic rings provides a motivation for investigating ring currents in molecules of an intermediate size. Here we show, using nuclear magnetic resonance spectroscopy and density functional theory, that a six-porphyrin nanoring template complex, with a diameter of 2.4 nanometres, is antiaromatic in its 4+ oxidation state (80 π electrons) and aromatic in its 6+ oxidation state (78 π electrons). The antiaromatic state has a huge paramagnetic susceptibility, despite having no unpaired electrons. This work demonstrates that a global ring current can be promoted in a macrocycle by adjusting its oxidation state

  13. Tree Rings: Timekeepers of the Past.

    ERIC Educational Resources Information Center

    Phipps, R. L.; McGowan, J.

    One of a series of general interest publications on science issues, this booklet describes the uses of tree rings in historical and biological recordkeeping. Separate sections cover the following topics: dating of tree rings, dating with tree rings, tree ring formation, tree ring identification, sample collections, tree ring cross dating, tree…

  14. Ring currents in azulene

    NASA Astrophysics Data System (ADS)

    Paxton, A. T.; Todorov, T. N.; Elena, A. M.

    2009-11-01

    We propose a self consistent polarisable ion tight binding theory for the study of push-pull processes in aromatic molecules. We find that the method quantitatively reproduces ab initio calculations of dipole moments and polarisability. We apply the scheme in a simulation which solves the time dependent Schrödinger equation to follow the relaxation of azulene from the second excited to the ground states. We observe rather spectacular oscillating ring currents which we explain in terms of interference between the HOMO and LUMO states.

  15. Wave structure in planetary rings

    NASA Astrophysics Data System (ADS)

    Horn, Linda Joyce

    1992-01-01

    Planetary rings contain a wealth of wavelike structure that is driven by gravitational resonance interactions with nearby satellites. Wave behavior is a powerful tool for estimating physical ring parameters that are key to our understanding of ring origin and evolution. A new technique, utilizing the Burg autoregressive power spectral algorithm, was developed for probing the physical characteristics of rings and for detecting waves that are not otherwise visible. Data from the Voyager photopolarimeter (PPS) stellar occultations by the rings of Saturn, Uranus, and Neptune and the Voyager radio science (RSS) occultation by Saturn's rings were used. Local surface mass density estimates are obtained from the dispersion of 40 spiral density waves in Saturn's A ring, including 10 weaker waves not previously analyzed. Surface mass densities vary from 20 to 60 gm sq cm. Increasing optical depth is not correlated with increasing surface mass density, especially after the Keeler gap, suggesting that ring particle size and composition are not uniform throughout the A ring. Saturn's A ring mass is reestimated using the surface mass densities and is 5.2 +/- 1.3 x 1021 gm. The wakes of Saturn's satellite Pan are not short timescale phenomena because the effects of Pan's gravitational perturbations persist for more than one Pan encounter. Four additional Pan wakes were discovered at longitudes greater than 360 deg. Collective effects such as collisions modify the wake dispersion more extensively at greater longitudes. Pan is the dominant mass in the Encke gap. A spiral density wave was detected inside the Uranian delta ring. Upper and lower bounds were estimated for the surface mass density of the delta ring 5 less than or equal to sigma less than or equal to 10 gm/sq cm, the viscosity 10 less than or equal to nu less than or equal to 40 sq cm/sec, and the local ring height 7 less than or equal to h less than or equal to 20 m. These values are comparable to the corresponding

  16. WISE Constraints on the Particle Properties in Saturn's Phoebe Ring

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.; Verbiscer, A. J.; Skrutskie, M. F.

    2012-05-01

    Saturn's diffuse outer Phoebe Ring is an immense disk-like structure oriented edge-on as viewed from Earth; it is 30 million km (500 Saturn ra dii) wide and 2.5 million km (40 Saturn radii) thick. The ring's particles are thought to originate primarily from the planet's dark irregular satellite Phoebe (mean radius 107km). The ring was discovered by Spitzer 24-micron imaging (Verbiscer et al., Nature 2009) and recently recovered by WISE (Skrutskie et al., DPS 2011) at 22 microns. The WISE images, which show the full extent of the ring for the first time, nicely complement the more sensitive but spatially-limited Spitzer data. Usually, ring particle populations can be determined observationally from spectral and phase angle information, but as observations of the Phoebe ring are extremely limited, we instead rely on dynamical arguments. Small particles in the Phoebe ring are expected to be driven to eccentricities in excess of Phoebe's e=0.16 by radiation pressure over 30-year timescales. Over million-year timescales, the dust distribution migrates inward via Poynting-Robertson drag, and most of the material finds its way onto the dark side of Iapetus. We model these processes numerically and build up synthetic ring profiles, making various assumptions about the unknown particle size distribution. We produce radial intensity profiles which we compare to the WISE data as well as vertical profiles which are most constrained by Spitzer. Our procedure is more robust than the onion-peeling technique used by ring scientists because it does not require the assumption of circular orbits. We find that the WISE data cannot be fit by a simple power law particle size distribution as is commonly assumed for rings. Instead, we show that the majority of the flux in the outer parts of the ring is be due to a significant excess of particles with sizes larger than several centimeters.

  17. Orbits of nine Uranian rings

    NASA Technical Reports Server (NTRS)

    Elliot, J. L.; French, R. G.; Frogel, J. A.; Elias, J. H.; Mink, D. J.; Liller, W.

    1981-01-01

    Observations of a stellar occultation by Uranus and its nine rings are presented and used to examine the structures and kinematics of the rings. The observations of the occultation of the K giant star KM 12 were obtained in the K band with the 4-m CTIO telescope at a signal-to-noise ratio higher than any previously obtained. Ring occultation profiles reveal the alpha ring to possibly have a double structure and less abrupt boundaries than the gamma ring, which exhibits diffraction fringes, while the eta ring is a broad ring with an unresolved narrow component at its inner edge. The present timing data, as well as previous occultation timings, are fit to a kinematic model in which all nine rings are treated as coplanar eclipses of zero inclination, precessing due to the zonal harmonics of the Uranian gravitational potential to obtain solutions for the ring orbits. Analysis of the residuals from the fitted orbits reveals that the proposed model is a good representation of ring kinematics. The reference system defined by the orbit solutions has also been used to obtain a value of 0.022 + or - 0.003 for the ellipticity of Uranus and a Uranian rotation period of 15.5 h.

  18. Revisiting stability of pickup ion rings

    NASA Astrophysics Data System (ADS)

    Florinski, V. A.; Niemiec, J.; Heerikhuisen, J.

    2015-12-01

    Do we really understand ring distribution stability in weakly turbulent plasmas? The first measurement of the interstellar magnetic fluctuation spectrum by Voyager 1 was consistent with interstellar Kolmogorov turbulence spectrum, ruling out any significant local wave sources, such as an instability. We show that both linear dispersion analysis and kinetic plasma computer simulations should be approached with much caution when drawing conclusions about the wave generation and resulting particle scattering in pitch angle, especially for very tenuous rings. Using hybrid-kinetic and PIC models we carefully examine the nonlinear phase of pickup ion (PUI) scattering on self-generated fluctuations to reveal a critical dependence on the number of pseudo-particles present in the simulation. It is shown that narrow rings modeled with very high number of particles (1 million per cell) could become stable in the nonlinear phase. The second part of this presentation deals with more realistic pickup rings derived from the distribution of primary energetic neutral atoms (ENAs) originating in the solar wind and the inner heliosheath. The width of these distributions allow them to remain stable on the timescales of at least a few months. These results lend additional support to the secondary PUI theory of the origin of the IBEX ribbon.

  19. The Charging of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Graps, Amara L.; Horanyi, M.; Havnes, O.; Gruen, E.

    2008-09-01

    Planetary rings have an undeniable aesthetic appeal, resulting in media icons of ringed planets as descriptive of the planetary sciences field as a whole. Such far-reaching symbolism might not be misplaced, however, because planetary rings represent a fundamental class of planetary structure that invites interdisciplinary investigations from specialists in dust, gravitational, plasma, collisional, and radiative transfer physics, due to: its sub-micron to meters-sized particles, its immersion in the planet's magnetic field, its embedded moonlets and its close proximity to the ringed planet's ionosphere and innermost moons. As such, planetary rings are a metaphoric bridge through a wide range of planetary physical processes. Processes to charge ring particles have different relative dynamical effects, dependent upon the rings' particle sizes, and the ring's plasma, magnetic and gravitational environments. This presentation will review what is known about the charging parameters and processes of planetary rings, in particular the sum of the individual currents from the time-varying charge dQ/dt, of the planetary ring particle. The individual currents depend on the environmental plasma conditions: number density, flow speed, temperature, and mass for the currents: electron and ion capture from the plasma, ion currents to a moving grain, photoelectron emission, secondary electron emission, thermionic effects, with stochastic charging influencing all of the above. Since rings are an ensemble of particles, ("cloud" Ring), we will define an ensemble, and consider the above currents, including those for the smallest ring particles, the dust particles, to arrive at a table giving charge potential and other relevant parameters.

  20. Rheology of Rings: Current Status and Future Challenges

    NASA Astrophysics Data System (ADS)

    McKenna, Gregory

    Understanding the dynamics of circular or ring-like polymers has been a subject of investigation since the 1980s and is one which remains an area that is not fully understood. Part of the reason for this is the difficulty of making synthetic rings of sufficient size to establish the nature of the entanglement dynamics, if entanglements even exist in these materials. Furthermore, there is now strong evidence that small amounts of linear impurities can impact the dynamics. Hence, one of the major challenges to our understanding of ring dynamics is to make large molecular weight rings of sufficient purity that the dynamics of the rings themselves can be determined. In the present work the current state of understanding of the dynamics of rings is outlined and current work from our group of collaborators to make extremely large circular polymers using Echeverria Coli as a route to make pure rings (circular DNA) in sufficient quantity and size to determine the dynamics of these materials will be shown. First results of ring dynamics in dilute solution are presented and new results on concentrated and entangled solutions will be discussed. Remaining challenges will be elucidated. Partially supported by the John R. Bradford Endowment and the Paul Whitfield Horn Professorship at Texas Tech University.

  1. Mechanical supporting ring structure

    NASA Astrophysics Data System (ADS)

    Tserodze, Sh.; Medzmariashvili, E.; Tusishvili, O.; Tsignadze, N.; Santiago-Prowald, J.; ‘t Klooster, C. G. M.; Medzmariashvili, N.

    2013-12-01

    Large deployable antenna reflectors are commonly employed for space missions. Scientific, telecommunications and earth observation applications are enabled due to the antenna gain provided by the large apertures (8-25 m). The most relevant requirements that drive the design are the size of the stowed package diameter (0.4-1.50 m), the mass (18-160 kg), the control of the deployment process, the accuracy and stability of the surface and the RF performance requirements. In this paper a new architecture of conical ring reflector is described, with the objective of providing a response to the mentioned requirements. The projected aperture range of 8-25 m is addressed, enabling to create offset reflectors of elliptical rim. The configuration is based on a double pantograph conical ring. It is an architecture suitable for reflector-based radar in LEO missions from P to C band, although the expected stiffness and stability can be seen as an asset for higher operational frequencies. The configuration of the structure is new and has been preliminarily discussed in the paper. Further investigations might well be of interest.

  2. Storage ring injection

    SciTech Connect

    Burke, R.J.

    1980-01-01

    Some basic issues involved in injecting the beam into storage rings with the principal parameters of those studied at the workshop have been considered. The main conclusion is that straightforward adjustments of the storage ring parameters makes injection easy. The largest number of injected turns is fourteen, and the phase space dilution allowance seems adequate to ensure very small beam loss during injection. The adjustments also result in lower bending magnet fields, and high field superconducting magnets (e.g., 5 Tesla) are not necessary. The design changes do not necessarily affect the Keil-Schnell criterion for stability of the longitudinal microwave instability, although that criterion appears to be irrelevant. Because the beams are expected to be unstable, but with slow growth rates, the vacuum chamber impedances required to give equal risetimes for the various designs are compared for systems posing various degrees of difficulty for injection. Finally, the impact of the parameters on cost is noted, and a system is considered that cuts the length of the linac in half by using doubly charged ions.

  3. Vortex and Rings

    NASA Image and Video Library

    2014-07-07

    NASA Cassini spacecraft captures three magnificent sights at once: Saturn north polar vortex and hexagon along with its expansive rings. The hexagon, which is wider than two Earths, owes its appearance to the jet stream that forms its perimeter. The jet stream forms a six-lobed, stationary wave which wraps around the north polar regions at a latitude of roughly 77 degrees North. This view looks toward the sunlit side of the rings from about 37 degrees above the ringplane. The image was taken with the Cassini spacecraft wide-angle camera on April 2, 2014 using a spectral filter which preferentially admits wavelengths of near-infrared light centered at 752 nanometers. The view was obtained at a distance of approximately 1.4 million miles (2.2 million kilometers) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 43 degrees. Image scale is 81 miles (131 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18274

  4. Buoyant Norbury's vortex rings

    NASA Astrophysics Data System (ADS)

    Blyth, Mark; Rodriguez-Rodriguez, Javier; Salman, Hayder

    2014-11-01

    Norbury's vortices are a one-parameter family of axisymmetric vortex rings that are exact solutions to the Euler equations. Due to their relative simplicity, they are extensively used to model the behavior of real vortex rings found in experiments and in Nature. In this work, we extend the original formulation of the problem to include buoyancy effects for the case where the fluid that lies within the vortex has a different density to that of the ambient. In this modified formulation, buoyancy effects enter the problem through the baroclinic term of the vorticity equation. This permits an efficient numerical solution of the governing equation of motion in terms of a vortex contour method that tracks the evolution of the boundary of the vortex. Finally, we compare our numerical results with the theoretical analysis of the short-time evolution of a buoyant vortex. Funded by the Spanish Ministry of Economy and Competitiveness through grant DPI2011-28356-C03-02 and by the London Mathematical Society.

  5. Ring Image Analyzer

    NASA Technical Reports Server (NTRS)

    Strekalov, Dmitry V.

    2012-01-01

    Ring Image Analyzer software analyzes images to recognize elliptical patterns. It determines the ellipse parameters (axes ratio, centroid coordinate, tilt angle). The program attempts to recognize elliptical fringes (e.g., Newton Rings) on a photograph and determine their centroid position, the short-to-long-axis ratio, and the angle of rotation of the long axis relative to the horizontal direction on the photograph. These capabilities are important in interferometric imaging and control of surfaces. In particular, this program has been developed and applied for determining the rim shape of precision-machined optical whispering gallery mode resonators. The program relies on a unique image recognition algorithm aimed at recognizing elliptical shapes, but can be easily adapted to other geometric shapes. It is robust against non-elliptical details of the image and against noise. Interferometric analysis of precision-machined surfaces remains an important technological instrument in hardware development and quality analysis. This software automates and increases the accuracy of this technique. The software has been developed for the needs of an R&TD-funded project and has become an important asset for the future research proposal to NASA as well as other agencies.

  6. Analysis of Double Ring Resonators using Method of Equating Fields

    NASA Astrophysics Data System (ADS)

    Althaf, Shahana

    Optical ring resonators have the potential to be integral parts of large scale photonic circuits. My thesis theoretically analyzes parallel coupled double ring resonators (DRRs) in detail. The analysis is performed using the method of equating fields (MEF) which provides an in depth understanding about the transmitted and reflected light paths in the structure. Equations for the transmitted and reflected fields are derived; these equations allow for unequal ring lengths and coupling coefficients. Sanity checks including comparison with previously studied structures are performed in the final chapter in order to prove the correctness of the obtained results.

  7. Storage ring: An advanced tool in modern research

    NASA Astrophysics Data System (ADS)

    Kienle, P.

    1998-11-01

    These introductory notes give a personal flavoured view on the developments, opportunities and perspectives of ion storage rings with cooling devices including some highlights of applications in various fields of research. First some historical remarks are made on the development of cooler rings and cooling techniques, highlighted by the observation of “orderliness” in cooled heavy ion beams. In the main part recent experimental highlights from storage rings in the fields of particle-, nuclear and atomic physics are reviewed. The lecture will end with a look at future projects and a dream.

  8. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance

    SciTech Connect

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings

  9. Cassini-VIMS Observations of Saturn's Rings at SOI

    NASA Astrophysics Data System (ADS)

    Nicholson, P. D.; Clark, R. N.; Cruikshank, D. P.; Showalter, M. R.; Sicardy, B.; Cassini VIMS

    2004-11-01

    Following the Cassini spacecraft's Saturn Orbit Insertion (SOI) burn on 1 July 2004, the Visual and Infrared Mapping Spectrometer (VIMS) obtained near-infrared spectra from 0.9 to 5.1 μ m in two continuous radial scans across the unlit side of the rings, at ranges of ˜30,000 km. The first scan covers the outer C and inner B rings at a phase angle, α = 82o and an emission angle, e = 47o, while the second covers the Cassini Division and entire A ring at α = 59o and e = 63o. The solar incidence angle was 114o and the radial resolution of both scans is 15-20 km, with sampling intervals of 2-3 km. Structurally, the rings appear to have changed little, if at all, since the Voyager observations in 1980/81 and the 28 Sgr occultations in 1989. This similarity extends even to the quasi-irregular structure which characterizes the inner B ring on scales of ˜100 km. Spectrally, all regions of the rings scanned are dominated by water ice, with prominent absorption bands at 1.55, 2.0 and 3.0 μ m, as well as weaker bands at 1.04 and 1.25 μ m seen primarily in the A and B rings. The ice bands are strongest in the middle A ring, somewhat weaker in the B ring, and much weaker in the C ring and Cassini Division. Locally, however, the fractional band depths appear to be independent of optical depth, suggesting that the light diffusely transmitted through the rings at moderate phase angles is dominated by single scattering. Regionally, the transitions between the C and B rings and between the Cassini Division and A ring are marked by gradual changes in band depth over radial distances of a few thousand km, perhaps indicative of ballistic redistribution of material. A broad reflectance maximum at 3.6 μ m, characteristic of ice grain sizes less than 100 μ m, is prominent everywhere but particularly strong in the outermost parts of the A ring, exterior to the Encke Gap. Besides water ice, the most noteworthy spectral feature is a broad, shallow absorption in the 0.9-1.8 μ m

  10. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance.

    PubMed

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R; Junge, Wolfgang; Khan, Shahid

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ring motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics that may

  11. Saturn's rings - A new survey

    NASA Technical Reports Server (NTRS)

    Cook, A. F.; Franklin, F. A.

    1977-01-01

    Observations of radar returns from Saturn's rings, together with radio interferometry of their absorption of radiation from the disk, combine to require an effective radius of ring particles of about 6 cm or larger. It is suggested that the ring particles may also include, in addition to the known ice constituent, a mixture of the clathrated hydrate of methane and ammonia hydrate. A two-density model for ring particles is possible in which a matrix of low density contains many nodules of higher-density ice particles; in this case, radii nearly as large as the observed ring thickness would be possible. Improved resolution in radio observations at 21 cm or, if necessary, at longer wavelengths for narrow ring openings is perhaps the most useful method for determining upper limits on the particle size.

  12. Ring current and radiation belts

    NASA Technical Reports Server (NTRS)

    Williams, D. J.

    1987-01-01

    Studies performed during 1983-1986 on the ring current, the injection boundary model, and the radiation belts are discussed. The results of these studies yielded the first observations on the composition and charge state of the ring current throughout the ring-current energy range, and strong observational support for an injection-boundary model accounting for the origins of radiation-belt particles, the ring current, and substorm particles observed at R less than about 7 earth radii. In addition, the results have demonstrated that the detection of energetic neutral atoms generated by charge-exchange interactions between the ring current and the hydrogen geocorona can provide global images of the earth's ring current and its spatial and temporal evolution.

  13. Reversible Rings with Involutions and Some Minimalities

    PubMed Central

    Fakieh, W. M.; Nauman, S. K.

    2013-01-01

    In continuation of the recent developments on extended reversibilities on rings, we initiate here a study on reversible rings with involutions, or, in short, ∗-reversible rings. These rings are symmetric, reversible, reflexive, and semicommutative. In this note we will study some properties and examples of ∗-reversible rings. It is proved here that the polynomial rings of ∗-reversible rings may not be ∗-reversible. A criterion for rings which cannot adhere to any involution is developed and it is observed that a minimal noninvolutary ring is of order 4 and that a minimal noncommutative ∗-reversible ring is of order 16. PMID:24489510

  14. Causes of Ring-Related Leg Injuries in Birds – Evidence and Recommendations from Four Field Studies

    PubMed Central

    Griesser, Michael; Schneider, Nicole A.; Collis, Mary-Anne; Overs, Anthony; Guppy, Michael; Guppy, Sarah; Takeuchi, Naoko; Collins, Pete; Peters, Anne; Hall, Michelle L.

    2012-01-01

    One of the main techniques for recognizing individuals in avian field research is marking birds with plastic and metal leg rings. However, in some species individuals may react negatively to rings, causing leg injuries and, in extreme cases, the loss of a foot or limb. Here, we report problems that arise from ringing and illustrate solutions based on field data from Brown Thornbills (Acanthiza pusilla) (2 populations), Siberian Jays (Perisoreus infaustus) and Purple-crowned Fairy-wrens (Malurus coronatus). We encountered three problems caused by plastic rings: inflammations triggered by material accumulating under the ring (Purple-crowned Fairy-wrens), contact inflammations as a consequence of plastic rings touching the foot or tibio-tarsal joint (Brown Thornbills), and toes or the foot getting trapped in partly unwrapped flat-band colour rings (Siberian Jays). Metal rings caused two problems: the edges of aluminium rings bent inwards if mounted on top of each other (Brown Thornbills), and too small a ring size led to inflammation (Purple-crowned Fairy-wrens). We overcame these problems by changing the ringing technique (using different ring types or larger rings), or using different adhesive. Additionally, we developed and tested a novel, simple technique of gluing plastic rings onto metal rings in Brown Thornbills. A review of studies reporting ring injuries (N = 23) showed that small birds (<55 g body weight) are more prone to leg infections while larger birds (>35 g) tend to get rings stuck over their feet. We give methodological advice on how these problems can be avoided, and suggest a ringing hazard index to compare the impact of ringing in terms of injury on different bird species. Finally, to facilitate improvements in ringing techniques, we encourage online deposition of information regarding ringing injuries of birds at a website hosted by the European Union for Bird Ringing (EURING). PMID:23300574

  15. Saturn's rings and associated ring plasma cavity: Evidence for slow ring erosion

    NASA Astrophysics Data System (ADS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-08-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C-ring, leading to field-aligned plasma transport to Saturn's ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma 'fountains'. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >109 years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  16. Saturn's Rings and Associated Ring Plasma Cavity: Evidence for Slow Ring Erosion

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Kurth, W. S.; Gurnett, D. A.; Persoon, A. M.; MacDowall, R. J.

    2017-01-01

    We re-examine the radio and plasma wave observations obtained during the Cassini Saturn orbit insertion period, as the spacecraft flew over the northern ring surface into a radial distance of 1.3 Rs (over the C-ring). Voyager era studies suggest the rings are a source of micro-meteoroid generated plasma and dust, with theorized peak impact-created plasma outflows over the densest portion of the rings (central B-ring). In sharp contrast, the Cassini Radio and Plasma Wave System (RPWS) observations identify the presence of a ring-plasma cavity located in the central portion of the B-ring, with little evidence of impact-related plasma. While previous Voyager era studies have predicted unstable ion orbits over the C- ring, leading to field-aligned plasma transport to Saturns ionosphere, the Cassini RPWS observations do not reveal evidence for such instability-created plasma fountains. Given the passive ring loss processes observed by Cassini, we find that the ring lifetimes should extend >10(exp 9) years, and that there is limited evidence for prompt destruction (loss in <100 Myrs).

  17. Pressure-Energized Seal Rings to Better Withstand Flows

    NASA Technical Reports Server (NTRS)

    Farner, Bruce

    2009-01-01

    approximate parallelogram would be pushed farther apart along a radius of the ring, thereby causing the polymeric ring material to push radially harder against the body sealing surface. From the radially innermost corner of the approximate parallelogram, the spring material would extend radially, then axially into recesses in the seal gland. These extensions would help to restrain the seal ring against ejection. A seat retainer would hold the sealing ring in the gland and form a mechanical compression seal to prevent or at least reduce leakage of pressurized fluid into the cavity behind the seal. However, because there would likely be a little leakage, the cavity behind the seal should be vented to the low pressure side to prevent buildup of pressure in the cavity over time; otherwise, the built-up pressure could cause ejection of the seal ring when the pressure on the high-pressure side was reduced. Polymeric seal-ring materials may not be able to withstand working conditions in applications that involve abrasive and/or hot working fluids. For such applications, all-metal seal rings may be preferred. The bottom part of Figure 2 shows one example of an alternative gland configuration with an all-metal seal ring.

  18. Split ring containment attachment device

    DOEpatents

    Sammel, Alfred G.

    1996-01-01

    A containment attachment device 10 for operatively connecting a glovebag 200 to plastic sheeting 100 covering hazardous material. The device 10 includes an inner split ring member 20 connected on one end 22 to a middle ring member 30 wherein the free end 21 of the split ring member 20 is inserted through a slit 101 in the plastic sheeting 100 to captively engage a generally circular portion of the plastic sheeting 100. A collar potion 41 having an outer ring portion 42 is provided with fastening means 51 for securing the device 10 together wherein the glovebag 200 is operatively connected to the collar portion 41.

  19. Saturn's Rings Edge-on

    NASA Technical Reports Server (NTRS)

    1995-01-01

    In one of nature's most dramatic examples of 'now-you see-them, now-you-don't', NASA's Hubble Space Telescope captured Saturn on May 22, 1995 as the planet's magnificent ring system turned edge-on. This ring-plane crossing occurs approximately every 15 years when the Earth passes through Saturn's ring plane.

    For comparison, the top picture was taken by Hubble on December 1, 1994 and shows the rings in a more familiar configuration for Earth observers.

    The bottom picture was taken shortly before the ring plane crossing. The rings do not disappear completely because the edge of the rings reflects sunlight. The dark band across the middle of Saturn is the shadow of the rings cast on the planet (the Sun is almost 3 degrees above the ring plane.) The bright stripe directly above the ring shadow is caused by sunlight reflected off the rings onto Saturn's atmosphere. Two of Saturn's icy moons are visible as tiny starlike objects in or near the ring plane. They are, from left to right, Tethys (slightly above the ring plane) and Dione.

    This observation will be used to determine the time of ring-plane crossing and the thickness of the main rings and to search for as yet undiscovered satellites. Knowledge of the exact time of ring-plane crossing will lead to an improved determination of the rate at which Saturn 'wobbles' about its axis (polar precession).

    Both pictures were taken with Hubble's Wide Field Planetary Camera 2. The top image was taken in visible light. Saturn's disk appears different in the bottom image because a narrowband filter (which only lets through light that is not absorbed by methane gas in Saturn's atmosphere) was used to reduce the bright glare of the planet. Though Saturn is approximately 900 million miles away, Hubble can see details as small as 450 miles across.

    The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science

  20. Ground Movement in SSRL Ring

    SciTech Connect

    Sunikumar, Nikita; /UCLA /SLAC

    2011-08-25

    Users of the Stanford Synchrotron Radiation Lightsource (SSRL) are being affected by diurnal motion of the synchrotron's storage ring, which undergoes structural changes due to outdoor temperature fluctuations. In order to minimize the effects of diurnal temperature fluctuations, especially on the vertical motion of the ring floor, scientists at SSRL tried three approaches: painting the storage ring white, covering the asphalt in the middle of the ring with highly reflective Mylar and installing Mylar on a portion of the ring roof and walls. Vertical motion in the storage ring is measured by a Hydrostatic Leveling System (HLS), which calculates the relative height of water in a pipe that extends around the ring. The 24-hr amplitude of the floor motion was determined using spectral analysis of HLS data, and the ratio of this amplitude before and after each experiment was used to quantitatively determine the efficacy of each approach. The results of this analysis showed that the Mylar did not have any significant effect on floor motion, although the whitewash project did yield a reduction in overall HLS variation of 15 percent. However, further analysis showed that the reduction can largely be attributed to a few local changes rather than an overall reduction in floor motion around the ring. Future work will consist of identifying and selectively insulating these local regions in order to find the driving force behind diurnal floor motion in the storage ring.

  1. Fingering inside the coffee ring

    NASA Astrophysics Data System (ADS)

    Weon, Byung Mook; Je, Jung Ho

    2013-01-01

    Colloidal droplets including micro- and nanoparticles generally leave a ringlike stain, called the “coffee ring,” after evaporation. We show that fingering emerges during evaporation inside the coffee ring, resulting from a bidispersed colloidal mixture of micro- and nanoparticles. Microscopic observations suggest that finger formation is driven by competition between the coffee-ring and Marangoni effects, especially when the inward Marangoni flow is overwhelmed by the outward coffee-ring flow. This finding could help to understand the variety of the final deposition patterns of colloidal droplets.

  2. Rings Around the Pole

    NASA Image and Video Library

    2005-01-20

    Atmospheric features in Saturn's north polar region are revealed in spectacular detail in this Cassini image, taken in the near infrared spectral region, where methane gas is not very absorbing. The dark shadows of Saturn's rings drape across the planet, creating the illusion of atmospheric bands. Dots of bright clouds give the appearance that this is an active place. The image was taken with the Cassini spacecraft wide angle camera on Dec. 14, 2004, at a distance of 717,800 kilometers (446,100 miles) from Saturn through a filter sensitive to wavelengths of infrared light centered at 939 nanometers. The image scale is about 43 kilometers (27 miles) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA06567

  3. Black ring deconstruction

    SciTech Connect

    Gimon, Eric; Gimon, Eric G.; Levi, Thomas S.

    2007-06-22

    We present a sample microstate for a black ring in four and five dimensional language. The microstate consists of a black string microstate with an additional D6-brane. We show that with an appropriate choice of parameters the piece involving the black string microstate falls down a long AdS throat, whose M-theory lift is AdS_3 x S2. We wrap a spinning dipole M2-brane on the S2 in the probe approximation. In IIA, this corresponds to a dielectric D2-brane carrying only D0-charge. We conjecture this is the firstapproximation to a cloud of D0-branes blowing up due to their non-abelian degrees of freedom and the Myers effect.

  4. A familiar ring?

    SciTech Connect

    Camack, M.J.

    1995-05-01

    These days, the 1984 divestiture of the regional Bell operating companies from AT&T and the succeeding competitive struggles among long-distance companies and equipment providers seem to ring loud and clear for those in the electric power business. The similarities are compelling: Advancements in technology, the clamor of customers for choice, and other natural pressures in the marketplace challenge the traditional structure of a natural monopoly, creating an opening for competition. Voila, deregulation. To gain expertise from the divestiture experience, several electric utility companies have dialed up former telecommunications executives and managers for their insights, hiring them for key positions in senior management. Veterans of telecommunications have instructive views on the similarities, differences, and lessons learned, especially in the areas of marketing and customer focus.

  5. Ring around the colloid

    NASA Astrophysics Data System (ADS)

    Cavallaro, Marcello, Jr.; Gharbi, Mohamed A.; Beller, Daniel A.; Čopar, Simon; Shi, Zheng; Kamien, Randall D.; Yang, Shu; Baumgart, Tobias; Stebe, Kathleen J.

    In this work, we show that Janus washers, genus-one colloids with hybrid anchoring conditions, form topologically required defects in nematic liquid crystals. Experiments under crossed polarizers reveal the defect structure to be a rigid disclination loop confined within the colloid, with an accompanying defect in the liquid crystal. When confined to a homeotropic cell, the resulting colloid-defect ring pair tilts relative to the far field director, in contrast to the behavior of toroidal colloids with purely homeotropic anchoring. We show that this tilting behavior can be reversibly suppressed by the introduction of a spherical colloid into the center of the toroid, creating a new kind of multi-shape colloidal assemblage.

  6. Synthesis of the EF-ring of ciguatoxin 3C based on the [2,3]-Wittig rearrangement and ring-closing olefin metathesis.

    PubMed

    Goto, Akiyoshi; Fujiwara, Kenshu; Kawai, Ayako; Kawai, Hidetoshi; Suzuki, Takanori

    2007-12-20

    The EF-ring segment of ciguatoxin 3C, a causative toxin of ciguatera fish poisoning, was synthesized in three major steps: 1,4-addition for the C20O-C27 bond connection, chirality transferring anti selective [2,3]-Wittig rearrangement for the construction of the anti-2-hydroxyalkyl ether part, and ring-closing olefin metathesis for the F-ring formation.

  7. The Phylogenetic Signature Underlying ATP Synthase c-Ring Compliance

    DOE PAGES

    Pandini, Alessandro; Kleinjung, Jens; Taylor, Willie R.; ...

    2015-09-01

    The proton-driven ATP synthase (FOF1) is comprised of two rotary, stepping motors (FO and F1) coupled by an elastic power transmission. The elastic compliance resides in the rotor module that includes the membrane-embedded FO c-ring. Proton transport by FO is firmly coupled to the rotation of the c-ring relative to other FO subunits (ab2). It drives ATP synthesis. We used a computational method to investigate the contribution of the c-ring to the total elastic compliance. We performed principal component analysis of conformational ensembles built using distance constraints from the bovine mitochondrial c-ring x-ray structure. Angular rotary twist, the dominant ringmore » motion, was estimated to show that the c-ring accounted in part for the measured compliance. Ring rotation was entrained to rotation of the external helix within each hairpin-shaped c-subunit in the ring. Ensembles of monomer and dimers extracted from complete c-rings showed that the coupling between collective ring and the individual subunit motions was independent of the size of the c-ring, which varies between organisms. Molecular determinants were identified by covariance analysis of residue coevolution and structural-alphabet-based local dynamics correlations. The residue coevolution gave a readout of subunit architecture. The dynamic couplings revealed that the hinge for both ring and subunit helix rotations was constructed from the proton-binding site and the adjacent glycine motif (IB-GGGG) in the midmembrane plane. IB-GGGG motifs were linked by long-range couplings across the ring, while intrasubunit couplings connected the motif to the conserved cytoplasmic loop and adjacent segments. The correlation with principal collective motions shows that the couplings underlie both ring rotary and bending motions. Noncontact couplings between IB-GGGG motifs matched the coevolution signal as well as contact couplings. The residue coevolution reflects the physiological importance of the dynamics

  8. How Jupiter's Ring Was Discovered.

    ERIC Educational Resources Information Center

    Elliot, James; Kerr, Richard

    1985-01-01

    "Rings" (by astronomer James Elliot and science writer Richard Kerr) is a nontechnical book about the discovery and exploration of ring systems from the time of Galileo to the era of the Voyager spacecraft. One of this book's chapters is presented. (JN)

  9. Uranus Rings in False Color

    NASA Image and Video Library

    1996-01-29

    This false-color view of the rings of Uranus was made from images taken by NASA Voyager 2 on Jan. 21, 1986. All nine known rings are visible here; the somewhat fainter, pastel lines seen between them are contributed by the computer enhancement. http://photojournal.jpl.nasa.gov/catalog/PIA00033

  10. Nardò Ring, Italy

    NASA Image and Video Library

    2008-04-08

    The Nardò Ring is a striking visual feature from space, and astronauts have photographed it several times. The Ring is a race car test track in Italy. This image was acquired by NASA Terra satellite on August 17. 2007.

  11. Running Rings Around the Web.

    ERIC Educational Resources Information Center

    McDermott, Irene E.

    1999-01-01

    Describes the development and current status of WebRing, a service that links related Web sites into a central hub. Discusses it as a viable alternative to other search engines and examines issues of free speech, use by the business sector, and implications for WebRing after its purchase by Yahoo! (LRW)

  12. Reversible Seeding in Storage Rings

    SciTech Connect

    Ratner, Daniel; Chao, Alex; /SLAC

    2011-12-14

    We propose to generate steady-state microbunching in a storage ring with a reversible seeding scheme. High gain harmonic generation (HGHG) and echo-enabled harmonic generation (EEHG) are two promising methods for microbunching linac electron beams. Because both schemes increase the energy spread of the seeded beam, they cannot drive a coherent radiator turn-by-turn in a storage ring. However, reversing the seeding process following the radiator minimizes the impact on the electron beam and may allow coherent radiation at or near the storage ring repetition rate. In this paper we describe the general idea and outline a proof-of-principle experiment. Electron storage rings can drive high average power light sources, and free-electron lasers (FELs) are now producing coherent light sources of unprecedented peak brightness While there is active research towards high repetition rate FELs (for example, using energy recovery linacs), at present there are still no convenient accelerator-based sources of high repetition rate, coherent radiation. As an alternative avenue, we recently proposed to establish steady-state microbunching (SSMB) in a storage ring. By maintaining steady-state coherent microbunching at one point in the storage ring, the beam generates coherent radiation at or close to the repetition rate of the storage ring. In this paper, we propose a method of generating a microbunched beam in a storage ring by using reversible versions of linac seeding schemes.

  13. How Jupiter's Ring Was Discovered.

    ERIC Educational Resources Information Center

    Elliot, James; Kerr, Richard

    1985-01-01

    "Rings" (by astronomer James Elliot and science writer Richard Kerr) is a nontechnical book about the discovery and exploration of ring systems from the time of Galileo to the era of the Voyager spacecraft. One of this book's chapters is presented. (JN)

  14. Contraceptive vaginal rings: a review.

    PubMed

    Brache, Vivian; Faundes, Anibal

    2010-11-01

    Development efforts on contraceptive vaginal rings were initiated over 40 years ago based on two principles: the capacity of the vaginal epithelium to absorb steroids and the capacity of elastomers to release these hormones at a nearly constant rate. Numerous models of contraceptive vaginal rings (CVRs) have been studied, but only two have reached the market: NuvaRing, a combined ring that releases etonogestrel (ENG) and ethinylestradiol (EE), and Progering, a progesterone-releasing ring for use in lactating women. The main advantages of CVRs are their effectiveness (similar to or slightly better than the pill), ease of use without the need of remembering a daily routine, user's ability to control initiation and discontinuation, nearly constant release rate allowing for lower doses, greater bioavailability and good cycle control with the combined ring. The main disadvantages are related to the mode of delivery; CVRs may cause vaginal discharge and complaints, ring expulsion is not uncommon, the ring may be felt during coitus and vaginal insertion may be unpleasant for some women. The studies reviewed in this article provide evidence that CVRs are safe, effective and highly acceptable to women. There is no doubt that CVRs offer a new, effective contraceptive option to women, expanding their available choices of hormonal contraception. Copyright © 2010 Elsevier Inc. All rights reserved.

  15. Ring Infiltrate in Staphylococcal Keratitis

    PubMed Central

    Wallang, Batriti S.; Sharma, Savitri; Sahu, Srikant K.; Mittal, Ruchi

    2013-01-01

    Smear and culture tests of corneal scrapings from a patient with a ring infiltrate confirmed significant growth of a Staphylococcus species resistant to fluoroquinolones. Because of nonresponse to medical management, the patient underwent therapeutic penetrating keratoplasty. Staphylococcal infection of the cornea may appear as a ring-like infiltrate that is recalcitrant to medical management. PMID:23100354

  16. Biomechanics of Corneal Ring Implants

    PubMed Central

    2015-01-01

    Purpose: To evaluate the biomechanics of corneal ring implants by providing a related mathematical theory and biomechanical model for the treatment of myopia and keratoconus. Methods: The spherical dome model considers the inhomogeneity of the tunica of the eye, dimensions of the cornea, lamellar structure of the corneal stroma, and asphericity of the cornea. It is used in this study for calculating a strengthening factor sf for the characterization of different ring-shaped corneal implant designs. The strengthening factor is a measure of the amount of strengthening of the cornea induced by the implant. Results: For ring segments and incomplete rings, sf = 1.0, which indicates that these implants are not able to strengthen the cornea. The intracorneal continuous complete ring (MyoRing) has a strengthening factor of up to sf = 3.2. The MyoRing is, therefore, able to strengthen the cornea significantly. Conclusions: The result of the presented biomechanical analysis of different ring-shaped corneal implant designs can explain the different postoperative clinical results of different implant types in myopia and keratoconus. PMID:26312619

  17. Rings Full of Waves (zoom)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This image shows a close-up view of a density wave in Saturn's A ring. It was taken by the narrow angle camera on the Cassini spacecraft after successful entry into Saturn's orbit. The view shows the dark, or unlit, side of the rings.

  18. Fibre ring cavity semiconductor laser

    SciTech Connect

    Duraev, V P; Medvedev, S V

    2013-10-31

    This paper presents a study of semiconductor lasers having a polarisation maintaining fibre ring cavity. We examine the operating principle and report main characteristics of a semiconductor ring laser, in particular in single- and multiple-frequency regimes, and discuss its application areas. (lasers)

  19. Simulating the Smallest Ring World of Chariklo

    NASA Astrophysics Data System (ADS)

    Michikoshi, Shugo; Kokubo, Eiichiro

    2017-03-01

    A ring system consisting of two dense narrow rings has been discovered around Centaur Chariklo. The existence of these rings around a small object poses various questions about their origin, stability, and lifetime. In order to understand the nature of Chariklo’s rings, we perform global N-body simulations of the self-gravitating collisional particle rings for the first time. We find that Chariklo should be denser than the ring material in order to avoid the rapid diffusion of the rings. If Chariklo is denser than the ring material, fine spiral structures called self-gravity wakes occur in the inner ring. These wakes accelerate the viscous spreading of the ring significantly and typically occur on timescales of about 100 {years} for m-sized ring particles, which is considerably shorter than the timescales suggested in previous studies. The existence of these narrow rings implies smaller ring particles or the existence of shepherding satellites.

  20. Ring lens focusing and push-pull tracking scheme for optical disk systems

    NASA Technical Reports Server (NTRS)

    Gerber, R.; Zambuto, J.; Erwin, J. K.; Mansuripur, M.

    1993-01-01

    An experimental comparison of the ring lens and the astigmatic techniques of generating focus-error-signal (FES) in optical disk systems reveals that the ring lens generates a FES over two times steeper than that produced by the astigmat. Partly due to this large slope and, in part, because of its diffraction-limited behavior, the ring lens scheme exhibits superior performance characteristics. In particular the undesirable signal known as 'feedthrough' (induced on the FES by track-crossings during the seek operation) is lower by a factor of six compared to that observed with the astigmatic method. The ring lens is easy to align and has reasonable tolerance for positioning errors.

  1. Black hole ringing, quasinormal modes, and light rings

    NASA Astrophysics Data System (ADS)

    Khanna, Gaurav; Price, Richard H.

    2017-04-01

    Modeling of gravitational waves from binary black hole inspiral has played an important role in the recent observations of such signals. The late-stage ringdown phase of the gravitational waveform is often associated with the null particle orbit ("light ring") of the black hole spacetime. With simple models we show that this link between the light ring and spacetime ringing is based more on the history of specific models than on an actual constraining relationship. We also show, in particular, that a better understanding of the dissociation of the two may be relevant to the astrophysically interesting case of rotating (Kerr) black holes.

  2. Radiation issues in a radioactive ion decay ring.

    PubMed

    Magistris, M; Silari, M

    2005-01-01

    In a beta-beam facility, a pure beam of electron neutrinos, or their antiparticles, are produced by the decay of fully stripped radioactive ions (6He and 18Ne) circulating in a storage ring. Since the beam is not extracted from the ring, all the particles will eventually be lost somewhere in the machine and thus activate the accelerator components and the surrounding concrete and rock. In particular, as nuclei change their charge in beta-decay, a large part of the particles will be lost in the arcs of the decay ring and mainly irradiate the magnets. The density of inelastic interactions of hadrons in the magnets, concrete and rock and the track-length distribution of secondary hadrons were calculated by means of the FLUKA Monte Carlo code. These values were used to estimate the induced radioactivity in the facility, the dose rates expected in the decay ring and the consequences for the environment.

  3. On the buckling of elastic rings by external confinement

    NASA Astrophysics Data System (ADS)

    Hazel, Andrew L.; Mullin, Tom

    2017-04-01

    We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff-Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement. This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'

  4. Observed structures at the edges of Saturn's rings

    NASA Astrophysics Data System (ADS)

    Albers, N.; Sremcevic, M.; Esposito, L. W.

    2014-04-01

    The edges of Saturn's rings exhibit structure on a range of spatial and temporal scales. Aside from the known variability in edge location many edges feature clumping on orbital timescales. In cases like the B and A ring outer edges even larger, more persistent objects have been observed. Most of these features and the underlying physical processing creating them have been associated with moon-induced perturbations. In addition tomoon-associated structures like wakes and gaps at the Encke and Keeler gap due to the presence of Pan and Daphnis respectively, parts of ring material is found truncated from the edges downstream of the moon. These gaps are about a few km wide and located a few tens of km from the edge. Using primarily Cassini UVIS occultations we investigate spatial and temporal morphology of ring edges.

  5. On the buckling of elastic rings by external confinement.

    PubMed

    Hazel, Andrew L; Mullin, Tom

    2017-05-13

    We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff-Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.'

  6. Impact of Saturn ring particles on Pioneer 11

    NASA Technical Reports Server (NTRS)

    Humes, D. H.; Oneal, R. L.; Kinard, W. H.; Alvarez, J. M.

    1980-01-01

    The detection of particles near the rings of Saturn by the meteoroid detection instrument on board Pioneer 11 is discussed. The instrument consists of 234 penetration detectors, distributed between two independent data channels each of which is designed to become inhibited for a period of 77 min after the registration of a penetration event in that channel. At least four particles penetrated the detectors in the 4.5 h period around Saturn periapsis at radial distances between 1.36 and 3.1 Saturn radii, a radial distribution inconsistent with the gravitational focusing of meteoroids. The detection of particles which may have been part of the E ring before the crossing of the ring plane suggests that this ring may be 1800 km thick, with an optical thickness greater than 10 to the -8th.

  7. Dione Before the Rings

    NASA Image and Video Library

    2015-11-23

    Saturn's rings are so expansive that they often sneak into Cassini's pictures of other bodies. Here, they appear with the planet in a picture taken during a close flyby of Dione. The flyby of Dione (698 miles or 1123 kilometers across) during which this image was taken was the last close encounter with this moon during Cassini's mission. The main goal of the flyby was to use the spacecraft as a probe to measure Dione's gravity field. However, scientists also managed to take some very close images of the surface. All of the data will be helpful to understand the interior structure and geological history of this distant, icy world. This view is centered on terrain at 7 degrees south latitude, 122 degrees west longitude. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 17, 2015. The view was obtained at a distance of approximately 48,000 miles (77,000 kilometers) from Dione and at a Sun-Dione-spacecraft, or phase angle of 35 degrees. Image scale is 1,520 feet (464 meters) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA18344

  8. Ring Buffered Network Bus

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This report describes the research effort to demonstrate the integration of a data sharing technology, Ring Buffered Network Bus, in development by Dryden Flight Research Center, with an engine simulation application, the Java Gas Turbine Simulator, in development at the University of Toledo under a grant from the Glenn Research Center. The objective of this task was to examine the application of the RBNB technologies as a key component in the data sharing, health monitoring and system wide modeling elements of the NASA Aviation Safety Program (AVSP) [Golding, 1997]. System-wide monitoring and modeling of aircraft and air safety systems will require access to all data sources which are relative factors when monitoring or modeling the national airspace such as radar, weather, aircraft performance, engine performance, schedule and planning, airport configuration, flight operations, etc. The data sharing portion of the overall AVSP program is responsible for providing the hardware and software architecture to access and distribute data, including real-time flight operations data, among all of the AVSP elements. The integration of an engine code capable of numerically "flying" through recorded flight paths and weather data using a software tool that allows for distributed access of data to this engine code demonstrates initial steps toward building a system capable of monitoring and modeling the National Airspace.

  9. Vortex formation in magnetic narrow rings

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.

    2002-03-01

    between the contacts, the magnetization is everywhere parallel to the current, and the resistance is high. After the second switching into the reverse `onion' state a domain wall is now present between the contacts. This means some of the magnetization in the transverse domain wall is perpendicular to the current and hence the resistance decreases. This shows that one can clearly distinguish between the onion and vortex state using MR measurements. In addition, using the field dependent voltage drop between different contacts, the switching field at which each part of the ring reverses can be determined. >From the second type of measurements clear hysteretic behaviour is seen, indicating that there is some domain wall pinning. This demonstrates that the position of the domain walls can be identified by looking at the voltage drop between different contacts. By measuring at different magnitudes of the applied field the pinning strength of the domain walls is determined, and in particular the dependence of the domain wall pinning on the notch size. Furthermore the structure of the domain wall changes for different notch sizes, and hence the contribution of the wall to the resistance changes as well. Real-time measurements between different contacts might allow for domain wall speed measurements and other domain wall propagation studies. References: [1] J. Rothman, M. Kläui, L. Lopez-Diaz, C.A.F. Vaz, A. Bleloch, J.A.C. Bland, Z. Cui, R. Speaks, Phys. Rev. Lett. 86 (2001) 1098. [2] Z. Cui, J. Rothman, M. Kläui, L. Lopez-Diaz, C.A.F. Vaz, J.A.C. Bland, to be published. [3] M. Kläui, L. Lopez-Diaz, J. Rothman, C.A.F. Vaz, J.A.C. Bland, Z. Cui, J. Magn. Magn. Mat., to be published. [4] L. Lopez-Diaz, J. Rothman, M. Kläui, J.A.C. Bland, IEEE Trans. Mag. 36 (2000) 3155. [5] C.A.F. Vaz, L. Lopez-Diaz, M. Kläui, J.A.C. Bland, T.L. Monchesky, J. Unguris, Z. Cui, 46th MMM Conference, Seattle, 2001. [6] R. D. McMichael and M. J. Donahue, IEEE Trans. Mag. 33, 4167-4169 (1997).

  10. Transverse electric field in a mesoscopic Luttinger-liquid ring

    NASA Astrophysics Data System (ADS)

    Šimánek, E.

    1999-08-01

    The electric field within a ring containing repulsively interacting electrons is estimated using the spinless Luttinger-liquid model extended to allow transverse excitations due to the radial centrifugal force. The radial voltage drop across a ring, threaded by the Aharonov-Bohm flux, consists of a flux-periodic part that is independent of the interaction, and a flux-independent part that is proportional to the square root of the inverse compressibility of the electron gas. The voltage drop obtained from perturbation theory is consistent with Bernoulli's equation.

  11. Ion Rings for Magnetic Fusion

    SciTech Connect

    Greenly, John, B.

    2005-07-31

    This Final Technical Report presents the results of the program, Ion Rings for Magnetic Fusion, which was carried out under Department of Energy funding during the period August, 1993 to January, 2005. The central objective of the program was to study the properties of field-reversed configurations formed by ion rings. In order to reach this objective, our experimental program, called the Field-reversed Ion Ring Experiment, FIREX, undertook to develop an efficient, economical technology for the production of field-reversed ion rings. A field-reversed configuration (FRC) in which the azimuthal (field-reversing) current is carried by ions with gyro-radius comparable to the magnetic separatrix radius is called a field-reversed ion ring. A background plasma is required for charge neutralization of the ring, and this plasma will be confined within the ring's closed magnetic flux. Ion rings have long been of interest as the basis of compact magnetic fusion reactors, as the basis for a high-power accelerator for an inertial fusion driver, and for other applications of high power ion beams or plasmas of high energy density. Specifically, the FIREX program was intended to address the longstanding question of the contribution of large-orbit ions to the observed stability of experimental FRCs to the MHD tilt mode. Typical experimental FRCs with s {approx} 2-4, where s is the ratio of separatrix radius to ion gyro-radius, have been stable to tilting, but desired values for a fusion reactor, s > 20, should be unstable. The FIREX ring would consist of a plasma with large s for the background ions, but with s {approx} 1 for the ring ions. By varying the proportions of these two populations, the minimum proportion of large-orbit ions necessary for stability could be determined. The incorporation of large-orbit ions, perhaps by neutral-beam injection, into an FRC has been advanced for the purpose of stabilizing, heating, controlling angular momentum, and aiding the formation of a

  12. Genetics Home Reference: ring chromosome 20 syndrome

    MedlinePlus

    ... Home Health Conditions ring chromosome 20 syndrome ring chromosome 20 syndrome Printable PDF Open All Close All ... to view the expand/collapse boxes. Description Ring chromosome 20 syndrome is a condition that affects the ...

  13. Galactic Behavior for the Outer B Ring

    NASA Image and Video Library

    2010-11-01

    Keeping a close watch on the outer portion of Saturn B ring, NASA Cassini spacecraft records the complex inward and outward movement of the edge of the ring. This ring movement resembles the suspected behavior of spiral disk galaxies.

  14. Particle properties and processes in Uranus' rings

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.; Brahic, A.; Burns, J. A.; Marouf, Essam A.

    1991-01-01

    The particle properties and processes in the Uranian rings are analyzed from Voyager observations and ground-based data. Occultation observations of the epsilon ring are interpreted to yield an effective size of the ring particles that exceeds 70 cm, a surface mass density that exceeds 80 g/sq cm, and a ring vertical thickness greater than tens of meters for solid ice particles. The particles forming the classic rings are dark and gray, with albedo of 0.014 +/-0.004. It is argued that the small amount of dust that exists in the classical rings and between the rings in bands is created by erosion of ring particles and unseen satellites resulting from collisions and micrometeoroid bombardment. As proposed for regions of the other known ring systems, new ring material can be continually created by the destruction of small moons near the rings, which may explain the youthful appearance of the Uranian rings.

  15. Modeling piston-ring dynamics, blowby, and ring-twist effects

    SciTech Connect

    Tian, T.; Noordzij, L.B.; Wong, V.W.; Heywood, J.B.

    1996-12-31

    A ring-dynamics and gas-flow model has been developed to study ring/groove contact, blowby, and the influence of ring static twist, keystone ring/groove configurations, and other piston and ring parameters. The model is developed for a ring pack with three rings. The dynamics of the top two rings and the gas pressures in the regions above the oil control ring are simulated. Distributions of oil film thickness and surface roughness on the groove and ring surfaces are assumed in the model to calculate the forces generated by the ring/groove contact. Ring static and dynamic twists are considered as well as different keystone ring/groove configurations. Ring dynamics and gas flows are coupled in the formulation and an implicit scheme is implemented, enabling the model to resolve detailed events such as ring flutter. Studies on a spark ignition engine found that static twist or, more generally speaking, the relative angle between rings and their grooves, has great influence on ring/groove contact characteristics, ring stability, and blowby. Ring flutter is found to occur for the second ring with a negative static twist under normal operating conditions and for the top ring with a negative static twist under high-speed/low-load operating conditions. Studies on a diesel engine show that different keystone ring/groove configurations result in different twist behaviors of the ring that may affect the wear pattern of the keystone ring running surfaces.

  16. Keck Adaptive Optics Imaging of Uranus and its Rings

    NASA Astrophysics Data System (ADS)

    de Pater, Imke; Roe, H.; Macintosh, B.; Gibbard, S.; Max, C.; Gavel, D.

    2000-10-01

    We observed Uranus with the recently commissioned AO/NIRSPEC system (Adaptive Optics system with the Near-Infrared echelle Spectrograph) on the 10-m W.M. Keck telescope, UT June 17 and 18, 2000. NIRSPEC allows one to take images and spectra simultaneously. Here we will discuss the images at wavelengths between 1 and 2.4 micron. Due to the location of the rings' pericenter, the rings were much brighter in the north than the south, which resulted in excellent ring images. Inside of the ɛ ring at least three more (individually slightly resolved) rings are visible: from the outside inwards these are: 1) combined δ ,γ ,η rings, 2) combined β ,α rings, and 3) combined 4,5,6 rings. On the planet itself we detected at least 8 different cloud features, five of which were in the northern hemisphere. Two features could be tracked over a 40-60 degree longitude range, and yield wind velocities of 175 +/- 35 m/s at a latitude of +30o, and of 120 +/- 40 m/s at +40o latitude. The highest latitude reached by HST NICMOS was +27o, where a velocity of 20 m/s was measured (Karkoschka, 1998). Has the wind speed changed? Or is there a very steep gradient in the profile? Our data suggest the wind profile to be similar to that derived for Neptune, though at reduced velocities. This research was supported in part by the STC Program of the National Science Foundation under Agreement No. AST-9876783, and in part under the auspices of the US Department of Energy at Lawrence Livermore National Laboratory, Univ. of Calif. under contract No. W-7405-Eng-48.

  17. The polar ring of Arp 230

    NASA Image and Video Library

    2015-01-26

    This Picture of the Week shows Arp 230, also known as IC 51, observed by the NASA/ESA Hubble Space Telescope. Arp 230 is a galaxy of an uncommon or peculiar shape, and is therefore part of the Atlas of Peculiar Galaxies produced by Halton Arp. Its irregular shape is thought to be the result of a violent collision with another galaxy sometime in the past. The collision could also be held responsible for the formation of the galaxy’s polar ring. The outer ring surrounding the galaxy consists of gas and stars and rotates over the poles of the galaxy. It is thought that the orbit of the smaller of the two galaxies that created Arp 230 was perpendicular to the disc of the second, larger galaxy when they collided. In the process of merging the smaller galaxy would have been ripped apart and may have formed the polar ring structure astronomers can observe today. Arp 230 is quite small for a lenticular galaxy, so the two original galaxies forming it must both have been smaller than the Milky Way. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by flickr user Det58. Links Atlas of Peculiar Galaxies

  18. Particle Simulations of Ion Rings for Magnetic Fusion.

    NASA Astrophysics Data System (ADS)

    Lyster, Peter Michael

    1987-09-01

    This thesis contains a numerical study of the dynamics of axis encircling charged particles in ion rings and layers. Part of this work deals with the coalescence of ion rings to form field reversed rings, which may be useful for Compact Torus magnetic fusion reactors. The coalescence of weak ion rings with Compact Toroids is also investigated. This is important because a component of energetic particles may help to maintain the flux or stabilize these configurations against a number of macroscopic magnetohydrodynamic instabilities. Several different types of particle codes are used. RINGA and CIDER are two and one half-dimensional codes in cylindrical axisymmetric geometry. For the RINGA code, a simple Ohm's law is used for modeling a resistive background plasma. For CIDER, the massless electron momentum equation is used for modeling a conductive background plasma. In a resistive plasma, ring coalescence can be achieved if the initial relative translational velocity is not excessive, and if the plasma conductivity is chosen to maximize the dissipation of ring energy. A theoretical and computational study is made of a mechanism by which ring translational energy is transferred to Alfven waves in a conductive plasma. A new collective phenomenon is discussed, whereby the merging of rings is improved if they have stronger initial self fields. A study is made of the coalescence of strong field-reversed ion rings in highly conductive plasmas, in which it is found that magnetic field line reconnection is an important process. Finally, a study of the magnetic compression of ion layers in conductive plasmas is presented. BAGSHAW, a one-dimensional particle code which treats the background plasma in the two fluid approximation, was developed for this purpose. Compression on a timescale which is comparable with the Alfven transit time may create considerable transients in the system. In a one-dimensional system, the plasma return current does not cancel the increase in the

  19. Ring-Ringlet Interactions in Saturn's C Ring

    NASA Technical Reports Server (NTRS)

    Rappaport, N. J.

    1997-01-01

    The overall obejective of this work is to derive a theoretical model for the formation of gaps harboring isolated ringlets in order to explain the presence of such features in Saturn's C ring and Cassini division.

  20. Reflex ring laser amplifier system

    DOEpatents

    Summers, Mark A.

    1985-01-01

    A laser pulse is injected into an unstable ring resonator-amplifier structure. Inside this resonator the laser pulse is amplified, spatially filtered and magnified. The laser pulse is recirculated in the resonator, being amplified, filtered and magnified on each pass. The magnification is chosen so that the beam passes through the amplifier in concentric non-overlapping regions similar to a single pass MOPA. After a number of passes around the ring resonator the laser pulse is spatially large enough to exit the ring resonator system by passing around an output mirror.

  1. Researches on the Piston Ring

    NASA Technical Reports Server (NTRS)

    Ehihara, Keikiti

    1944-01-01

    In internal combustion engines, steam engines, air compressors, and so forth, the piston ring plays an important role. Especially, the recent development of Diesel engines which require a high compression pressure for their working, makes, nowadays, the packing action of the piston ring far more important than ever. Though a number of papers have been published in regard to researches on the problem of the piston ring, none has yet dealt with an exact measurement of pressure exerted on the cylinder wall at any given point of the ring. The only paper that can be traced on this subject so far is Mr. Nakagawa's report on the determination of the relative distribution of pressure on the cylinder wall, but the measuring method adopted therein appears to need further consideration. No exact idea has yet been obtained as to how the obturation of gas between the piston and cylinder, the frictional resistance of the piston, and the wear of the cylinder wall are affected by the intensity and the distribution of the radial pressure of the piston ring. Consequently, the author has endeavored, by employing an apparatus of his own invention, to get an exact determination of the pressure distribution of the piston ring. By means of a newly devised ring tester, to which piezoelectricity of quartz was applied, the distribution of the radial pressure of many sample rings on the market was accurately determined. Since many famous piston rings show very irregular pressure distribution, the author investigated and achieved a manufacturing process of the piston ring which will exert uniform pressure on the cylinder wall. Temperature effects on the configuration and on the mean spring power have also been studied. Further, the tests were performed to ascertain how the gas tightness of the piston ring may be affected by the number or spring power. The researches as to the frictional resistance between the piston ring and the cylinder wall were carried out, too. The procedure of study, and

  2. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059478 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst (left) and NASA astronaut Reid Wiseman, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  3. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059467 (10 July 2014) --- In the International Space Station's Kibo laboratory, European Space Agency astronaut Alexander Gerst and NASA astronaut Reid Wiseman (mostly obscured), both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  4. SPHERES-RINGS Time Lapse

    NASA Image and Video Library

    2014-07-10

    ISS040-E-059344 (10 July 2014) --- In the International Space Station’s Kibo laboratory, NASA astronaut Reid Wiseman (left) and European Space Agency astronaut Alexander Gerst, both Expedition 40 flight engineers, conduct a session with a pair of bowling-ball-sized free-flying satellites known as Synchronized Position Hold, Engage, Reorient, Experimental Satellites, or SPHERES. Surrounding the two SPHERES mini-satellites is ring-shaped hardware known as the Resonant Inductive Near-field Generation System, or RINGS. SPHERES-RINGS seeks to demonstrate wireless power transfer between satellites at a distance for enhanced operations.

  5. Codes over infinite family of rings : Equivalence and invariant ring

    NASA Astrophysics Data System (ADS)

    Irwansyah, Muchtadi-Alamsyah, Intan; Muchlis, Ahmad; Barra, Aleams; Suprijanto, Djoko

    2016-02-01

    In this paper, we study codes over the ring Bk=𝔽pr[v1,…,vk]/(vi2=vi,∀i =1 ,…,k ) . For instance, we focus on two topics, i.e. characterization of the equivalent condition between two codes over Bk using a Gray map into codes over finite field 𝔽pr, and finding generators for invariant ring of Hamming weight enumerator for Euclidean self-dual codes over Bk.

  6. Photometric Analysis of the Jovian Ring System and Modeling of Ring Origin and Evolution

    NASA Technical Reports Server (NTRS)

    Esposito, L. W.

    2003-01-01

    We have successfully completed the work described in our proposal. The work supported by this grant resulted in the publication of the following paper: Brooks, S. M., L. W. Esposito, M. R. Showalter, and H. B. Throop. 2002. The size distribution of Jupiter's main ring from Galileo imaging and spectroscopy. Icarus, in press. This was also the major part of Dr. Shawn Brooks PhD dissertation. Dr. Brooks gave oral presentations on this work at the Lunar and Planetary Conference, the annual meetings of the Division for Planetary Sciences of the American Astronomical Society, the annual meetings of the European Geophysical Society, the international Jupiter Conference in Boulder, the Jupiter after Galileo and Cassini Conference in Lisbon and to the Working Group in Non-Linear Dynamics in Potsdam, Germany. This work was reviewed in: Esposito, L. W. 2002. Planetary rings. Rep. hog. Phys. 65, 1741-1783. Planetary rings. LASP reprint 874. Online at http://stacks.iop.org/RoPP/65/1741. Dr. Esposito gave presentations at schools and over the internet on the results of this work. Dr. Brooks lectured in undergraduate and graduate classes on Jupiter's rings, and on the meaning of his research. In August 2003, Dr. Shawn Brooks received the Phd degree from the University of Colorado in Astrophysical and Planetary Sciences.

  7. Raschig ring HDS catalysts reduce pressure drop

    SciTech Connect

    Moyse, B.

    1984-12-31

    Many hydroprocessing units have a limit on their run length imposed by bed plugging. As opposed to catalyst deactivation, bed plugging can cause pressure drop over the reactor or first reactor in the train to develop rapidly. For this reason many reactor designs call for the use of scale baskets together with grading of topping material and/or catalyst in the top bed of the lead reactor. Nevertheless, many plants have a history of unfavorable pressure drop development. Some refiners must regularly practice catalyst skimming operations. In such pressure drop limiting cases the use of Raschig ring catalysts as part of the reactor fill can markedly improve the pressure drop situation.

  8. NMR studies of exocyclic 1,N sup 2 -propanodeoxyguanosine adducts (X) opposite purines in DNA duplexes: Protonated X(syn)ter dot A(anti) pairing (acidic pH) and X(syn)ter dot G(anti) pairing (neutral pH) at the lesion site

    SciTech Connect

    Kouchakdjian, M.; Gao, X.; Patel, D. ); Marinelli, E.; Johnson, F.; Grollman, A. )

    1989-06-27

    Proton and phosphorus two-dimensional NMR studies are reported for the complementary d(C1-A2-T3-G4-X5-G6-T7-A8-C9){center dot}d(G10-T11-A12-C13-A14-C15-A16-T17-G18) nonanucleotide duplex (designated X{center dot}A 9-mer) that contains a 1,N{sup 2}-propanodeoxyguanosine exocyclic adduct, X5, opposite deoxyadenosine A14 in the center of the helix. The NMR studies detect a pH-dependent conformational transition; this paper focuses on the structure present at pH 5.8. The two-dimensional NOESY studies of the X{center dot}A 9-mer duplex in H{sub 2}O and D{sub 2}O solution establish that X5 adopts a syn orientation while A14 adopts an anti orientation about the glycosidic bond at the lesion site. At pH 5.8, the observed NOE between the H8 proton of X5 and the H2 proton of A14 in the X{center dot}A 9-mer duplex demonstrates unequivocally the formation of the protonated X5(syn){center dot}A14(anti) pair. A perturbation in the phosphodiester backbone is detected at the C13-A14 phosphorus located at the lesion site by {sup 31}P NMR spectroscopy. The two-dimensional NMR studies have been extended to the related complementary X{center dot}G 9-mer duplex that contains a central X5{center dot}G14 lesion in a sequence that is otherwise identical with the X{center dot}A 9-mer duplex. The NMR experimental parameters are consistent with formation of a pH-independent X5(syn){center dot}G14(anti) pair stabilized by two hydrogen bonds with the 1,N{sup 2}-propano exocyclic adduct of X5(syn) located in the major groove.

  9. Structures of exocyclic R,R- and S,S-N(6),N(6)-(2,3-dihydroxybutan-1,4-diyl)-2'-deoxyadenosine adducts induced by 1,2,3,4-diepoxybutane.

    PubMed

    Kowal, Ewa A; Seneviratne, Uthpala; Wickramaratne, Susith; Doherty, Kathleen E; Cao, Xiangkun; Tretyakova, Natalia; Stone, Michael P

    2014-05-19

    1,3-Butadiene (BD) is an industrial and environmental chemical present in urban air and cigarette smoke, and is classified as a human carcinogen. It is oxidized by cytochrome P450 to form 1,2,3,4-diepoxybutane (DEB); DEB bis-alkylates the N(6) position of adenine in DNA. Two enantiomers of bis-N(6)-dA adducts of DEB have been identified: R,R-N(6),N(6)-(2,3-dihydroxybutan-1,4-diyl)-2'-deoxyadenosine (R,R-DHB-dA), and S,S-N(6),N(6)-(2,3-dihydroxybutan-1,4-diyl)-2'-deoxyadenosine (S,S-DHB-dA) [ Seneviratne , U. , Antsypovich , S. , Dorr , D. Q. , Dissanayake , T. , Kotapati , S. , and Tretyakova , N. ( 2010 ) Chem. Res. Toxicol. 23 , 1556 -1567 ]. Herein, the R,R-DHB-dA and S,S-DHB-dA adducts have been incorporated into the 5'-d(C(1)G(2)G(3)A(4)C(5)X(6)A(7)G(8)A(9)A(10)G(11))-3':5'-d(C(12)T(13)T(14)C(15)T(16)T(17)G(18)T(19)C(20)C(21)G(22))-3' duplex [X(6) = R,R-DHB-dA (R(6)) or S,S-DHB-dA (S(6))]. The structures of the duplexes were determined by molecular dynamics calculations, which were restrained by experimental distances obtained from NMR data. Both the R,R- and S,S-DHB-dA adducts are positioned in the major groove of DNA. In both instances, the bulky 3,4-dihydroxypyrrolidine rings are accommodated by an out-of-plane rotation about the C6-N(6) bond of the bis-alkylated adenine. In both instances, the directionality of the dihydroxypyrrolidine ring is evidenced by the pattern of NOEs between the 3,4-dihydroxypyrrolidine protons and DNA. Also in both instances, the anti conformation of the glycosyl bond is maintained, which combined with the out-of-plane rotation about the C6-N(6) bond, allows the complementary thymine, T(17), to remain stacked within the duplex, and form one hydrogen bond with the modified base, between the imine nitrogen of the modified base and the T(17) N3H imino proton. The loss of the second Watson-Crick hydrogen bonding interaction at the lesion sites correlates with the lower thermal stabilities of the R,R- and S,S-DHB-dA duplexes, as

  10. Ultraviolet Ring Around the Galaxies

    NASA Image and Video Library

    2010-08-11

    Astronomers have found unexpected rings and arcs of ultraviolet light around a selection of galaxies, four of which are shown here as viewed by NASA and the European Space Agency Hubble Space Telescope.

  11. Black rings at large D

    NASA Astrophysics Data System (ADS)

    Tanabe, Kentaro

    2016-02-01

    We study the effective theory of slowly rotating black holes at the infinite limit of the spacetime dimension D. This large D effective theory is obtained by integrating the Einstein equation with respect to the radial direction. The effective theory gives equations for non-linear dynamical deformations of a slowly rotating black hole by effective equations. The effective equations contain the slowly rotating Myers-Perry black hole, slowly boosted black string, non-uniform black string and black ring as stationary solutions. We obtain the analytic solution of the black ring by solving effective equations. Furthermore, by perturbation analysis of effective equations, we find a quasinormal mode condition of the black ring in analytic way. As a result we confirm that thin black ring is unstable against non-axisymmetric perturbations. We also include 1 /D corrections to the effective equations and discuss the effects by 1 /D corrections.

  12. Dissipative ring solitons with vorticity.

    PubMed

    Soto-Crespo, J M; Akhmediev, N; Mejia-Cortés, C; Devine, N

    2009-03-16

    We study dissipative ring solitons with vorticity in the frame of the (2+1)-dimensional cubic-quintic complex Ginzburg-Landau equation. In dissipative media, radially symmetric ring structures with any vorticity m can be stable in a finite range of parameters. Beyond the region of stability, the solitons lose the radial symmetry but may remain stable, keeping the same value of the topological charge. We have found bifurcations into solitons with n-fold bending symmetry, with n independent on m. Solitons without circular symmetry can also display (m + 1)-fold modulation behaviour. A sequence of bifurcations can transform the ring soliton into a pulsating or chaotic state which keeps the same value of the topological charge as the original ring.

  13. Ring Beholds a Delicate Flower

    NASA Image and Video Library

    2005-02-11

    NASA Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom.

  14. Physical processes in planetary rings

    NASA Technical Reports Server (NTRS)

    Burns, Joseph A.

    1991-01-01

    A summary of research performed in 1990 is presented. The subject areas covered include perturbed narrow rings and the dynamics of circumplanetary dust. Progress made in the area of perturbed narrow rings includes: (1) the possible discovery of an undocumented moonlet in the environs of Saturn's F ring; and (2) the investigation of the consequences of a close satellite perturbing a narrow ring using numerical simulation. Progress made in the area of circumplanetary dust includes: (1) studies of the motion of circumplanetary dust under the action of radiation pressure and various electromagnetic processes; and (2) the initiation of a systematic explanation of the curious consequences of some of the perturbations that act on small particles.

  15. Earhart in the A Ring

    NASA Image and Video Library

    2013-08-19

    Cassini scientists continue their quest to understand the origin and evolution of the newly discovered features observed in Saturn A ring which have become known as propellers as shown in this image from NASA Cassini spacecraft.

  16. Vortex rings in Bose gas

    SciTech Connect

    Belyaev, S. T.

    2016-06-15

    We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.

  17. Large Double-ringed Basin

    NASA Image and Video Library

    2000-08-05

    Taken about 40 minutes before NASA Mariner 10 made its close approach to Mercury on Sept. 21,1974, this picture shows a large double-ringed basin center of picture located in the planet south polar region

  18. Dust Impact Detection by the Cassini Langmuir Probe in Saturn's E ring

    NASA Astrophysics Data System (ADS)

    Hsu, H.-W.; Wahlund, J.-E.; Morooka, M.; Kempf, S.; Horanyi, M.

    2015-10-01

    In this work, we present preliminary analysis of dust impact detections recorded by the Cassini Langmuir probe (LP) in Saturn's E ring. These signals appear as sharp spikes in the LP current-voltage (I-V) curves and show clear correlation with the E ring dust density. The statistical analysis will help to understand the nature of these detections as well as provide an alternative method to study the densest part of the E ring.

  19. Collector ring project at FAIR

    NASA Astrophysics Data System (ADS)

    Dolinskii, A.; Berkaev, D.; Blell, U.; Dimopoulou, C.; Gorda, O.; Leibrock, H.; Litvinov, S.; Laier, U.; Koop, I.; Schurig, I.; Starostenko, A.; Shatunov, P.; Weinrich, U.

    2015-11-01

    The collector ring is a dedicated ring for fast cooling of ions coming from separators at the FAIR project. To accommodate optimal technical solutions, a structure of a magnet lattice was recently reviewed and modified. Consequently, more appropriate technical solutions for the main magnets could be adopted. A general layout and design of the present machine is shown. The demanding extraction schemes have been detailed and open design issues were completed.

  20. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, Richard N.; Martin, Juergen; Paldus, Barbara A.; Xie, Jinchun

    1999-01-01

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS).

  1. Ring resonant cavities for spectroscopy

    DOEpatents

    Zare, R.N.; Martin, J.; Paldus, B.A.; Xie, J.

    1999-06-15

    Ring-shaped resonant cavities for spectroscopy allow a reduction in optical feedback to the light source, and provide information on the interaction of both s- and p-polarized light with samples. A laser light source is locked to a single cavity mode. An intracavity acousto-optic modulator may be used to couple light into the cavity. The cavity geometry is particularly useful for Cavity Ring-Down Spectroscopy (CRDS). 6 figs.

  2. Resonance capture and Saturn's rings

    SciTech Connect

    Patterson, C.W.

    1986-05-01

    We have assigned the resonances apparently responsible for the stabilization of the Saturn's shepherd satellites and for the substructure seen in the F-ring and the ringlets in the C-ring. We show that Saturn's narrow ringlets have a substructure determined by three-body resonances with Saturn's ringmoons and the sun. We believe such resonances have important implications to satellite formation. 17 refs., 1 fig., 1 tab.

  3. The Case for Massive and Ancient Rings of Saturn

    NASA Astrophysics Data System (ADS)

    Esposito, Larry W.

    2016-04-01

    Analysis of Voyager and Pioneer 11 results give a mass for Saturn's rings, M = 5 x 10-8 Msat. This is about the mass of Saturn's small moon Mimas. This has been interpreted as a lower limit to the ring mass (Esposito et al 1983), since the thickest parts of the rings were not penetrated by the stellar occultstion, and this calculation assumes an unvarying particle size throughout the rings. Because the rings are constantly bombarded by micrometeroids, their current composition of nearly pure water ice implies such low mass rings must have formed recently. The case is par-ticularly strong for Saturn's A ring, where the data are the best, implying the A ring is less than 10% of the age of the Saturn (Esposito 1986). Cassini results com-pound this problem. UVIS spectra are consistent with either young rings or rings about 10x as massive as the Voyager estimate (Elliott and Esposito (2011). CDA confirms the impacting mass flux is similar to that as-sumed for the pollution calculations (Kempf etal 2015). VIMS analysis of density wave signatures in the B ring gives a value of about 1/3 the Voyager value (Hedmann etal 2016). This VIMS result implies the rings are even younger! The problem is that young rings are very unlikely to be formed recently, meaning that we live in a very special epoch, following some unlikely recent origin… like disruption of a medium sized moon or capture of the fragments of a disrupted comet. This paradox (Charnoz etal 2009) is unre-solved. Alternative interpretations: To take the VIMS results at face value, Saturn's low mass rings must be very young. The optically thick B ring must be made of small, porous or fractal particles. This is hard to understand, since the particles are continually colliding every few hours and temporary aggregates will stir the collision velocities to higher values. An alternative is that we accept the higher mass interpretation of the Pioneer 11 results (Esposito etal 2008) using the granola bar model of Colwell

  4. Faint F Ring and Prometheus

    NASA Image and Video Library

    2016-11-21

    Surface features are visible on Saturn's moon Prometheus in this view from NASA's Cassini spacecraft. Most of Cassini's images of Prometheus are too distant to resolve individual craters, making views like this a rare treat. Saturn's narrow F ring, which makes a diagonal line beginning at top center, appears bright and bold in some Cassini views, but not here. Since the sun is nearly behind Cassini in this image, most of the light hitting the F ring is being scattered away from the camera, making it appear dim. Light-scattering behavior like this is typical of rings comprised of small particles, such as the F ring. This view looks toward the unilluminated side of the rings from about 14 degrees below the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Sept. 24, 2016. The view was acquired at a distance of approximately 226,000 miles (364,000 kilometers) from Prometheus and at a sun-Prometheus-spacecraft, or phase, angle of 51 degrees. Image scale is 1.2 miles (2 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA20508

  5. History of Neptune's Ring Arcs

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Colwell, J. E.; Canup, R. M.

    1997-07-01

    The recent dynamical calculations for Neptune's Adams ring arcs by Foryta and Sicardy (1996) and Hanninen and Porco (1997) determine the basic evolutionary parameters for this system. The ring evolution is dominated by stochastic events, particularly chaotic motion that causes a migration between the corotation sites (FS96) and collisions near quadrature (HP97). A basic problem is that the high velocity collisions that produce the dusty arcs at the Galatea corotation resonances rapidly depopulate these sites (Colwell and Esposito 1990). With the new results in hand for the evolution of the ring particles over periods of less than a century, we can now calculate the long-term stochastic evolution of the Adams ring. Using a finite Markov chain as a model for this stochastic process, we follow the suggestion by FS96 that corotation sites provide preferential locations for accretion. A more general conclusion is that the longitudinal concentration of material in a few nearby sites (and that the majority of the Adams ring material is residing there) requires either an exceedingly recent event (EC92) or that the corotation sites be absorbing states of the Markov chain.In the latter case, the competing processes of chaotic diffusion and frustrated accretion can provide the arc and clump features as recurrent transient events near the Roche limit. Similar phenomena would be expected for Saturn's F and G rings.

  6. Classifying Saturn's F Ring Strands

    NASA Astrophysics Data System (ADS)

    Albers, Nicole; Sremcevic, M.; Esposito, L. W.; Colwell, J. E.

    2009-09-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) High Speed Photometer (HSP) has recorded more than 113 stellar occultations by Saturn's F ring providing measurements with ring plane resolutions of a few dozen meters and better. Inner and outer F ring strands have been seen throughout the Cassini mission where they revealed themselves as non-continuous, azimuthally and temporally highly variable structures. In the light of a more accurate orbit description of the F ring core we find evidence for a ring that becomes dynamically more active as the system approaches anti-apse alignment with Prometheus. This is consistent with the observed increased strand activity. A recent strand that morphologically resembles the core is the strongest seen to date and points to the intricate relation between core and strands indicating the strands' violent creation. Using more than 150 identifications of various strands, we trace their kinematics and infer dynamical timescales and photometric properties. Implications for the dynamical evolution of the F ring will be discussed. This research was supported by the Cassini Project.

  7. Collar nut and thrust ring

    DOEpatents

    Lowery, Guy B.

    1991-01-01

    A collar nut comprises a hollow cylinder having fine interior threads at one end for threadably engaging a pump mechanical seal assembly and an inwardly depending flange at the other end. The flange has an enlarged portion with a groove for receiving an O-ring for sealing against the intrusion of pumpage from the exterior. The enlarged portion engages a thrust ring about the pump shaft for crushing a hard O-ring, such as a graphite O-ring. The hard O-ring seals the interior of the mechanical seal assembly and pump housing against the loss of lubricants or leakage of pumpage. The fine threads of the hollow cylinder provide the mechanical advantage for crushing the hard O-ring evenly and easily with a hand tool from the side of the collar nut rather than by tightening a plurality of bolts from the end and streamlines the exterior surface of the mechanical seal. The collar nut avoids the spatial requirements of bolt heads at the end of a seal and associated bolt head turbulence.

  8. Physics of Jupiter's Gossamer Rings

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.; Krueger, H.

    2007-10-01

    Thebe's gossamer ring, the outermost and faintest of Jupiter's rings, has an outward extension that we have previously argued is due to a shadow resonance (Hamilton 2003, DPS meeting #35, #11.09). A shadow resonance arises from the abrupt shutoff of photoelectric charging when a dust particle enters Jupiter's shadow which, in turn, affects the strength of the electromagnetic perturbation from the planet's intense magnetic field. The result is a coupled oscillation between a particle's orbital eccentricity and its semimajor axis. Ring material spreads outward from Thebe while maintaining its vertical thickness just as observed by Galileo imaging. In addition to cameras, the Galileo spacecraft was also equipped with dust and plasma detectors. The spacecraft made two passes through the ring and its dust detector found that 1) dust fluxes drop immediately interior to Thebe's orbit, 2) some grains have inclinations in excess of 20 degrees and 3) submicron particles are present in the Amalthea ring in much greater numbers than in the Thebe ring. These findings can all be explained in the context of our shadow resonance model: the inner boundary is a direct consequence of the conservation of the Electromagnetic Jacobi Constant, the high inclinations are forced by a vertical resonance, and the excess submicron particles are a consequence of the weakening of electromagnetic forces in the vicinity of synchronous orbit. In this talk, we will present the data sets as well as detailed numerical simulations that back up these claims.

  9. Of Rings and Volcanoes

    NASA Astrophysics Data System (ADS)

    2002-01-01

    Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and the DESPA and DASGAL laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA infra-red camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für Extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. Saturn - Lord of the rings ESO PR Photo 04a/02 ESO PR Photo 04a/02 [Preview - JPEG: 460 x 400 pix - 54k] [Normal - JPEG: 1034 x 800 pix - 200k] Caption : PR Photo 04a/02 shows the giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocussing" for this observation. More details in the text. Technical information about this photo is available below. This NAOS/CONICA image of Saturn ( PR Photo 04a/02 ), the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. It was only recently observed in visible light from the ground with a telescope at the Pic du Midi Observatory in the Pyrenees (France) - this is the first infrared image to

  10. Characteristic Time of the Magnetospheric Ring Current Decay FROM EXPIREMENT AND THEORY

    NASA Astrophysics Data System (ADS)

    Biktash(Sizova), L. Z.; Korotova, G. I.

    2006-12-01

    The magnetospheric ring current particles are the most dynamic part of the Earth's radiation belts especially during geomagnetic storms. The processes of the magnetospheric ring current decay are studied as a function of the solar wind electric field. It is shown that the ring current dissipation rate is different during the main and recovery phase of geomagnetic storms. The characteristic time of the ring current decay in the main phase is independent of storm intensity and equals 4 hours. The characteristic time of the ring current decay in a recovery phase increases with storm intensity. We examine the ring current ion lifetimes for the possible mechanisms of its decay. Coulomb scattering, charge exchange and plasma instability mechanisms are used for estimation of lifetime of electrons, protons, helium, and oxygen ions. The values of the characteristic lifetime of ring current dissipation obtained from experiment and theory are compared. It is shown that during main and recovery phase of magnetic storm the different mechanisms can play main role in dissipation of the ring current. Very short characteristic decay time during main phase of geomagnetic storms is associated with plasma instabilities. The available ion composition data of the ring current make possible to assume that the ring current decay is accounted for by ion composition variations with changing the intensity (and hence position) of the ring current and/or by a rise of energetic ion fraction on low L-shells.

  11. Rhinoplasty: the lateral crura-alar ring.

    PubMed

    Daniel, Rollin K; Palhazi, Peter; Gerbault, Olivier; Kosins, Aaron M

    2014-05-01

    Rhinoplasty surgeons routinely excise or incise the lateral crura despite nostril rim retraction, bossa, and collapse. Given recent emphasis on preserving the lateral crura, a review of the lateral crura's anatomy is warranted. The authors quantify specific anatomical aspects of the lateral crura in cadavers and clinical patients. This was a 2-part investigation, consisting of a prospective clinical measurement study of 40 consecutive rhinoplasty patients (all women) and 20 fresh cadaver dissections (13 males, 1 female). In the clinical phase, the alar cartilages were photographed intraoperatively and alar position (ie, orientation), axis, and width were measured. Cadaver dissections concentrated on parts of the lateral crura (alar cartilages and alar ring) that were inaccessible clinically. Average clinical patient age was 28 years (range, 14-51 years). Average cadaver age was 74 (range, 57-88 years). Clinically, the distance of the lateral crura from the mid-nostril point averaged 5.9 mm, and the cephalic orientation averaged 43.6 degrees. The most frequent configuration of the axis was smooth-straight in the horizontal axis and a cephalic border higher than the caudal border in the vertical axis. Maximal lateral crura width averaged 10.1 mm. In the cadavers, average lateral crural dimensions were 23.4 mm long, 6.4 mm wide at the domal notch, 11.1 mm wide at the so-designated turning point (TP), and 0.5 mm thickness. The accessory cartilage chain was present in all dissections. The lateral crura-alar ring was present in all dissections as a circular ring continuing around toward the anterior nasal spine but not abutting the pyriform. The lateral crura (1) begins at the domal notch and ends at the accessory cartilages, (2) exhibits a distinct TP from the caudal border, (3) has distinct horizontal and vertical vectors, and (4) should have a caudal border higher than the cephalic border. Alar malposition may be associated with position, orientation, or configuration.

  12. Microstrip Ring Resonator for Soil Moisture Measurements

    NASA Technical Reports Server (NTRS)

    Sarabandi, Kamal; Li, Eric S.

    1993-01-01

    Accurate determination of spatial soil moisture distribution and monitoring its temporal variation have a significant impact on the outcomes of hydrologic, ecologic, and climatic models. Development of a successful remote sensing instrument for soil moisture relies on the accurate knowledge of the soil dielectric constant (epsilon(sub soil)) to its moisture content. Two existing methods for measurement of dielectric constant of soil at low and high frequencies are, respectively, the time domain reflectometry and the reflection coefficient measurement using an open-ended coaxial probe. The major shortcoming of these methods is the lack of accurate determination of the imaginary part of epsilon(sub soil). In this paper a microstrip ring resonator is proposed for the accurate measurement of soil dielectric constant. In this technique the microstrip ring resonator is placed in contact with soil medium and the real and imaginary parts of epsilon(sub soil) are determined from the changes in the resonant frequency and the quality factor of the resonator respectively. The solution of the electromagnetic problem is obtained using a hybrid approach based on the method of moments solution of the quasi-static formulation in conjunction with experimental data obtained from reference dielectric samples. Also a simple inversion algorithm for epsilon(sub soil) = epsilon'(sub r) + j(epsilon"(sub r)) based on regression analysis is obtained. It is shown that the wide dynamic range of the measured quantities provides excellent accuracy in the dielectric constant measurement. A prototype microstrip ring resonator at L-band is designed and measurements of soil with different moisture contents are presented and compared with other approaches.

  13. Aharonov-Bohm oscillations in phosphorene quantum rings

    NASA Astrophysics Data System (ADS)

    Li, L. L.; Moldovan, D.; Vasilopoulos, P.; Peeters, F. M.

    2017-05-01

    The Aharonov-Bohm (AB) effect in square phosphorene quantum rings, with armchair and zigzag edges, is investigated using the tight-binding method. The energy spectra and wave functions of such rings, obtained as a function of the magnetic flux Φ threading the ring, are strongly influenced by the ring width W , an in-plane electric field Ep, and a side-gating potential Vg. Compared to a square dot, the ring shows an enhanced confinement due to its inner edges and an interedge coupling along the zigzag direction, both of which strongly affect the energy spectrum and the wave functions. The energy spectrum that is gapped consists of a regular part, of conduction (valence) band states, that shows the usual AB oscillations in the higher- (lower-) energy region, and of edge states, in the gap, that exhibit no AB oscillations. As the width W decreases, the AB oscillations become more distinct and regular and their period is close to Φ0/2 , where the flux quantum Φ0=h /e is the period of an ideal circular ring (W →0 ). Both the electric field Ep and the side-gating potential Vg reduce the amplitude of the AB oscillations. The amplitude can be effectively tuned by Ep or Vg and exhibits an anisotropic behavior for different field directions or side-gating configurations.

  14. On the synthesis, measurement and applications of octanuclear heterometallic rings

    NASA Astrophysics Data System (ADS)

    Faust, T. B.

    Inorganic macrocycles have stimulated interest in recent years for their magnetic properties, their associated host-guest chemistry and their aesthetically appealing structures. These characteristics have led to suggestions that they could be exploited for the purposes of ion recognition, catalysis, as single molecule magnets, MRI agents, antibacterial agents and as part of larger architectures in a molecular machine. This thesis explores the properties of a group of chromium(III) macrocycles, with functionality tailored towards different pursuits. Firstly the magnetic properties of a newly synthesised family of ring dimers are investigated. The nature of magnetic exchange within each ring leads to a net electronic spin which, it has been proposed, could represent a quantum binary digit within a quantum information processing system. By linking together pairs of rings, the degree of inter-ring communication can be determined. Such interactions are important for the correlation of spin as initiation of quantum entanglement, a pre-requisite for quantum computing. The rings can also act as fluoro-metallocrown, hosting the molecule which templated their formation. A range of rings with different guests are synthesised and their solid and solution state structures are explored. On templating about bulky dialykyl amines hybrid organic-inorganic rotaxanes are formed where the guest is fixed. In contrast when using small amines and alkali metals, exchange of guests is possible. The dynamics of all of these systems are investigated with proton NMR, quite remarkable for such highly paramagnetic complexes.

  15. A ring system detected around the Centaur (10199) Chariklo.

    PubMed

    Braga-Ribas, F; Sicardy, B; Ortiz, J L; Snodgrass, C; Roques, F; Vieira-Martins, R; Camargo, J I B; Assafin, M; Duffard, R; Jehin, E; Pollock, J; Leiva, R; Emilio, M; Machado, D I; Colazo, C; Lellouch, E; Skottfelt, J; Gillon, M; Ligier, N; Maquet, L; Benedetti-Rossi, G; Ramos Gomes, A; Kervella, P; Monteiro, H; Sfair, R; El Moutamid, M; Tancredi, G; Spagnotto, J; Maury, A; Morales, N; Gil-Hutton, R; Roland, S; Ceretta, A; Gu, S-h; Wang, X-b; Harpsøe, K; Rabus, M; Manfroid, J; Opitom, C; Vanzi, L; Mehret, L; Lorenzini, L; Schneiter, E M; Melia, R; Lecacheux, J; Colas, F; Vachier, F; Widemann, T; Almenares, L; Sandness, R G; Char, F; Perez, V; Lemos, P; Martinez, N; Jørgensen, U G; Dominik, M; Roig, F; Reichart, D E; LaCluyze, A P; Haislip, J B; Ivarsen, K M; Moore, J P; Frank, N R; Lambas, D G

    2014-04-03

    Hitherto, rings have been found exclusively around the four giant planets in the Solar System. Rings are natural laboratories in which to study dynamical processes analogous to those that take place during the formation of planetary systems and galaxies. Their presence also tells us about the origin and evolution of the body they encircle. Here we report observations of a multichord stellar occultation that revealed the presence of a ring system around (10199) Chariklo, which is a Centaur--that is, one of a class of small objects orbiting primarily between Jupiter and Neptune--with an equivalent radius of 124 ±  9 kilometres (ref. 2). There are two dense rings, with respective widths of about 7 and 3 kilometres, optical depths of 0.4 and 0.06, and orbital radii of 391 and 405 kilometres. The present orientation of the ring is consistent with an edge-on geometry in 2008, which provides a simple explanation for the dimming of the Chariklo system between 1997 and 2008, and for the gradual disappearance of ice and other absorption features in its spectrum over the same period. This implies that the rings are partly composed of water ice. They may be the remnants of a debris disk, possibly confined by embedded, kilometre-sized satellites.

  16. Wearable Ring-Based Sensing Platform for Detecting Chemical Threats.

    PubMed

    Sempionatto, Juliane R; Mishra, Rupesh K; Martín, Aida; Tang, Guangda; Nakagawa, Tatsuo; Lu, Xiaolong; Campbell, Alan S; Lyu, Kay Mengjia; Wang, Joseph

    2017-10-11

    This work describes a wireless wearable ring-based multiplexed chemical sensor platform for rapid electrochemical monitoring of explosive and nerve-agent threats in vapor and liquid phases. The ring-based sensor system consists of two parts: a set of printed electrochemical sensors and a miniaturized electronic interface, based on a battery-powered stamp-size potentiostat, for signal processing and wireless transmission of data. A wide range of electrochemical capabilities have thus been fully integrated into a 3D printed compact ring structure, toward performing fast square-wave voltammetry and chronoamperometric analyses, along with interchangeable screen-printed sensing electrodes for the rapid detection of different chemical threats. High analytical performance is demonstrated despite the remarkable miniaturization and integration of the ring system. The attractive capabilities of the wearable sensor ring system have been demonstrated for sensitive and rapid voltammetric and amperometric monitoring of nitroaromatic and peroxide explosives, respectively, along with amperometric biosensing of organophosphate (OP) nerve agents. Such ability of the miniaturized wearable sensor ring platform to simultaneously detect multiple chemical threats in both liquid and vapor phases and alert the wearer of such hazards offers considerable promise for meeting the demands of diverse defense and security scenarios.

  17. Chromosomal breakpoints characterization of two supernumerary ring chromosomes 20.

    PubMed

    Guediche, N; Brisset, S; Benichou, J-J; Guérin, N; Mabboux, P; Maurin, M-L; Bas, C; Laroudie, M; Picone, O; Goldszmidt, D; Prévot, S; Labrune, P; Tachdjian, G

    2010-02-01

    The occurrence of an additional ring chromosome 20 is a rare chromosome abnormality, and no common phenotype has been yet described. We report on two new patients presenting with a supernumerary ring chromosome 20 both prenatally diagnosed. The first presented with intrauterine growth retardation and some craniofacial dysmorphism, and the second case had a normal phenotype except for obesity. Conventional cytogenetic studies showed for each patient a small supernumerary marker chromosome (SMC). Using fluorescence in situ hybridization, these SMCs corresponded to ring chromosomes 20 including a part of short and long arms of chromosome 20. Detailed molecular cytogenetic characterization showed different breakpoints (20p11.23 and 20q11.23 for Patient 1 and 20p11.21 and 20q11.21 for Patient 2) and sizes of the two ring chromosomes 20 (13.6 Mb for case 1 and 4.8 Mb for case 2). Review of the 13 case reports of an extra r(20) ascertained postnatally (8 cases) and prenatally (5 cases) showed varying degrees of phenotypic abnormalities. We document a detailed molecular cytogenetic chromosomal breakpoints characterization of two cases of supernumerary ring chromosomes 20. These results emphasize the need to characterize precisely chromosomal breakpoints of supernumerary ring chromosomes 20 in order to establish genotype-phenotype correlation. This report may be helpful for prediction of natural history and outcome, particularly in prenatal diagnosis. Copyright 2010 Wiley-Liss, Inc.

  18. Structures of Exocyclic R,R- and S,S-N6,N6-(2,3-Dihydroxybutan-1,4-diyl)-2′-Deoxyadenosine Adducts Induced by 1,2,3,4-Diepoxybutane

    PubMed Central

    2015-01-01

    1,3-Butadiene (BD) is an industrial and environmental chemical present in urban air and cigarette smoke, and is classified as a human carcinogen. It is oxidized by cytochrome P450 to form 1,2,3,4-diepoxybutane (DEB); DEB bis-alkylates the N6 position of adenine in DNA. Two enantiomers of bis-N6-dA adducts of DEB have been identified: R,R-N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2′-deoxyadenosine (R,R-DHB-dA), and S,S-N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2′-deoxyadenosine (S,S-DHB-dA) [SeneviratneU., AntsypovichS., DorrD. Q., DissanayakeT., KotapatiS., and TretyakovaN. (2010) Chem. Res. Toxicol.23, 1556−156720873715]. Herein, the R,R-DHB-dA and S,S-DHB-dA adducts have been incorporated into the 5′-d(C1G2G3A4C5X6A7G8A9A10G11)-3′:5′-d(C12T13T14C15T16T17G18T19C20C21G22)-3′ duplex [X6 = R,R-DHB-dA (R6) or S,S-DHB-dA (S6)]. The structures of the duplexes were determined by molecular dynamics calculations, which were restrained by experimental distances obtained from NMR data. Both the R,R- and S,S-DHB-dA adducts are positioned in the major groove of DNA. In both instances, the bulky 3,4-dihydroxypyrrolidine rings are accommodated by an out-of-plane rotation about the C6-N6 bond of the bis-alkylated adenine. In both instances, the directionality of the dihydroxypyrrolidine ring is evidenced by the pattern of NOEs between the 3,4-dihydroxypyrrolidine protons and DNA. Also in both instances, the anti conformation of the glycosyl bond is maintained, which combined with the out-of-plane rotation about the C6-N6 bond, allows the complementary thymine, T17, to remain stacked within the duplex, and form one hydrogen bond with the modified base, between the imine nitrogen of the modified base and the T17 N3H imino proton. The loss of the second Watson–Crick hydrogen bonding interaction at the lesion sites correlates with the lower thermal stabilities of the R,R- and S,S-DHB-dA duplexes, as compared to the corresponding unmodified duplex. The reduced base stacking at the

  19. Accretion in Saturn's F Ring

    NASA Astrophysics Data System (ADS)

    Meinke, B. K.; Esposito, L. W.; Stewart, G.

    2012-12-01

    Saturn's F ring is the solar system's principal natural laboratory for direct observation of accretion and disruption processes. The ring resides in the Roche zone, where tidal disruption competes with self-gravity, which allows us to observe the lifecycle of moonlets. Just as nearby moons create structure at the B ring edge (Esposito et al. 2012) and the Keeler gap (Murray 2007), the F ring "shepherding" moons Prometheus and Pandora stir up ring material and create observably changing structures on timescales of days to decades. In fact, Beurle et al (2010) show that Prometheus makes it possible for "distended, yet gravitationally coherent clumps" to form in the F ring, and Barbara and Esposito (2002) predicted a population of ~1 km bodies in the ring. In addition to the observations over the last three decades, the Cassini Ultraviolet Imaging Spectrograph (UVIS) has detected 27 statistically significant features in 101 occultations by Saturn's F ring since July 2004. Seventeen of those 27 features are associated with clumps of ring material. Two features are opaque in occultation, which makes them candidates for solid objects, which we refer to as Moonlets. The 15 other features partially block stellar signal for 22 m to just over 3.7 km along the radial expanse of the occultation. Upon visual inspection of the occultation profile, these features resemble Icicles, thus we will refer to them as such here. The density enhancements responsible for such signal attenuations are likely due to transient clumping of material, evidence that aggregations of material are ubiquitous in the F ring. Our lengthy observing campaign reveals that Icicles are likely transient clumps, while Moonlets are possible solid objects. Optical depth is an indicator of clumping because more-densely aggregated material blocks more light; therefore, it is natural to imagine moonlets as later evolutionary stage of icicle, when looser clumps of material compact to form a feature that appears

  20. Study of Intrabeam Scattering in Low Energy Electron Rings

    SciTech Connect

    Venturini, Marco

    2002-08-08

    The paper contains a study of intrabeam scattering in a low energy electron storage ring to be used as part of a Compton back-scattering x-ray source. We discuss time evolution of emittance and dependence of IBS growth rates on lattice parameters.

  1. Mode Orientation Control For Sapphire Dielectric Ring Resonator

    NASA Technical Reports Server (NTRS)

    Santiago, David G.; Dick, G. John; Prata, Aluizio

    1996-01-01

    Small sapphire tuning wedge used in technique for solving mode-purity problem associated with sapphire dielectric-ring resonator part of cryogenic microwave frequency discriminator. Breaks quasi-degeneracy of two modes and allows selective coupling to just one mode. Wedge mounted on axle entering resonator cavity and rotated while resonator cryogenically operating in vacuum. Furthermore, axle moved vertically to tune resonant frequency.

  2. Injection and Extraction Lines for the ILC Damping Rings

    SciTech Connect

    Reichel, Ina

    2007-06-20

    The current design for the injection and extraction linesintoand out of the ILC Damping Rings is presented as well as the designfor the abort line. Due to changes of the geometric boundary conditionsby other subsystems of the ILC, a modular approach has been used to beable to respond to recurring layout changes whilereusing previouslydesigned parts.

  3. Study for ILC Damping Ring at KEKB

    SciTech Connect

    Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; Pivi, M.; /SLAC

    2011-11-04

    ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

  4. Double acting stirling engine piston ring

    DOEpatents

    Howarth, Roy B.

    1986-01-01

    A piston ring design for a Stirling engine wherein the contact pressure between the piston and the cylinder is maintained at a uniform level, independent of engine conditions through a balancing of the pressure exerted upon the ring's surface and thereby allowing the contact pressure on the ring to be predetermined through the use of a preloaded expander ring.

  5. Plasma deposited rider rings for hot displacer

    DOEpatents

    Kroebig, Helmut L.

    1976-01-01

    A hot cylinder for a cryogenic refrigerator having two plasma spray deposited rider rings of a corrosion and abrasion resistant material provided in the rider ring grooves, wherein the rider rings are machined to the desired diameter and width after deposition. The rider rings have gas flow flats machined on their outer surface.

  6. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, T.C.

    1999-08-24

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion. 3 figs.

  7. Concentric ring flywheel without expansion separators

    DOEpatents

    Kuklo, Thomas C.

    1999-01-01

    A concentric ring flywheel wherein the adjacent rings are configured to eliminate the need for differential expansion separators between the adjacent rings. This is accomplished by forming a circumferential step on an outer surface of an inner concentric ring and forming a matching circumferential step on the inner surface of an adjacent outer concentric ring. During operation the circumferential steps allow the rings to differentially expand due to the difference in the radius of the rings without the formation of gaps therebetween, thereby eliminating the need for expansion separators to take up the gaps formed by differential expansion.

  8. Micromagnetic calculation of magnetization reversal in magnetic rings

    NASA Astrophysics Data System (ADS)

    Lopez-Diaz, Luis

    2002-03-01

    The success of using patterned magnetic nanoelements in Magnetic Random Access Memories (MRAM) depends entirely on our ability to control accurately their switching fields. In a recent study1, we showed that micron-sized narrow rings present well defined stable states and nucleation-free switching between them. In the first part of the talk we review our experimental studies on ring magnets. Pre-patterned Si(100) substrates were used to grow free-standing epitaxial ring magnets of Cu(100)/Co(100)/Cu(100)/Si(100) with 1.8 mm outer diameter, 1.2 mm inner diameter and 34 nm thickness. The samples were magnetically characterised using specially adapted magneto-optic Kerr effect. The measurements show that a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a second state which is also stable at remanence and undergoes a simple and well characterised nucleation free domain wall propagation switching process. Moreover, it is confirmed that the rings reverse by falling into vortex states with different circulation when the field is applied in opposite directions. This means a particular vortex state (clockwise or counter-clockwise) can be prepared using a uniform field only, which can be important for technological applications. In the second part of the talk we use micromagnetic simulations to further explore the potential performance of narrow rings as memory cells in MRAM devices in terms of scalability and switching speed. We introduce two artificial notches at the outer surface of the rings in order to control accurately the depinning fields for the domain walls. According to our simulations, well defined onion states1 and switching by domain wall motion can be achieved for ring diameters down 180 nm. In order to speed up the switching process, two different approaches are considered. In the first one, a field pulse is

  9. Grinding Parts For Automatic Welding

    NASA Technical Reports Server (NTRS)

    Burley, Richard K.; Hoult, William S.

    1989-01-01

    Rollers guide grinding tool along prospective welding path. Skatelike fixture holds rotary grinder or file for machining large-diameter rings or ring segments in preparation for welding. Operator grasps handles to push rolling fixture along part. Rollers maintain precise dimensional relationship so grinding wheel cuts precise depth. Fixture-mounted grinder machines surface to quality sufficient for automatic welding; manual welding with attendant variations and distortion not necessary. Developed to enable automatic welding of parts, manual welding of which resulted in weld bead permeated with microscopic fissures.

  10. Ringing in an HNBody Upgrade

    NASA Astrophysics Data System (ADS)

    Rimlinger, Thomas; Hamilton, Douglas; Hahn, Joseph M.

    2017-06-01

    We are in the process of developing a useful extension to the N-body integrator HNBody (Rauch & Hamilton 2002), enabling it to simulate a viscous, self-gravitating ring orbiting an oblate body. Our algorithm follows that used in the symplectic integrator epi_int (Hahn & Spitale 2013), in which the ring is simulated as many (~100) interacting, elliptic, confocal streamlines. This idea was first introduced in an analytic context by Goldreich & Tremaine (1979) and enabled rapid progress in the theory of ring evolution; since then, such discretization has been standard in the literature. While we adopt epi_int’s streamline formalism, we nevertheless improve upon its design in several ways. Epi_int uses epicyclic elements in its drift step; approximating these elements introduces small, systematic errors that build up with time. We sidestep this problem by instead using the more traditional Keplerian osculating elements. In addition, epi_int uses several particles per wire to effectively calculate the inter-gravitational forces everywhere along each streamline. We replicate this ability but can often gain a speed boost by using a single tracer particle per streamline; while this restricts us to simulating rings dominated by the m = 1 mode, this is typical of most observed narrow eccentric ringlets. We have also extended epi_int’s two dimensional algorithm into 3D. Finally, whereas epi_int is written in IDL, HNBody is written in C, which yields considerably faster integrations.Braga-Ribas et al. (2014) reported a set of narrow rings orbiting the Centaur Chariklo, but neither their investigation nor that of Pan & Wu (2016) yielded a satisfactory origin and evolution scenario. Eschewing the assumption that such rings must be short-lived, we instead argue (as in Rimlinger et al. 2016) that sufficiently eccentric rings can self-confine for hundreds of millions of years while circularizing. In this case, Chariklo may have formed rings as a KBO. We are working towards

  11. Intrinsic structure in Saturn's rings

    NASA Astrophysics Data System (ADS)

    Albers, N.

    2015-10-01

    Saturn's rings are the most prominent in our Solar system and one example of granular matter in space. Dominated by tides and inelastic collisions the system is highly flattened being almost 300000km wide while only tens of meters thick. Individual particles are composed of primarily water ice and range from microns to few tens of meters in size. Apparent patterns comprise ringlets, gaps, kinematic wakes, propellers, bending waves, and the winding spiral arms of density waves. These large-scale structures are perturbations foremost created by external as well as embedded moons. Observations made by the Cassini spacecraft currently in orbit around Saturn show these structures in unprecedented detail. But high-resolution measurements reveal the presence of small-scale structures throughout the system. These include self-gravity wakes (50-100m), overstable waves (100-300m), subkm structure at the A and B ring edges, "straw" and "ropy" structures (1-3km), and the C ring "ghosts". Most of these had not been anticipated and are found in perturbed regions, driven by resonances with external moons, where the system undergoes periodic phases of compression and relaxation that correlate with the presence of structure. High velocity dispersion and the presence of large clumps imply structure formation on time scales as short as one orbit (about 10 hours). The presence of these intrinsic structures is seemingly the response to varying local conditions such as internal density, optical depth, underlying particle size distribution, granular temperature, and distance from the central planet. Their abundance provides evidence for an active and dynamic ring system where aggregation and fragmentation are ongoing on orbital timescales. Thus a kinetic description of the rings may be more appropriate than the fluid one. I will present Cassini Ultraviolet Spectrometer (UVIS) High Speed Photometer (HSP) occultations, Voyager 1 and 2 Imaging Science Subsystem (ISS), and high

  12. Hydrodynamic Simulations of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Miller, Jacob; Stewart, G. R.; Esposito, L. W.

    2013-10-01

    Simulations of rings have traditionally been done using N-body methods, granting insight into the interactions of individual ring particles on varying scales. However, due to the scale of a typical ring system and the sheer number of particles involved, a global N-body simulation is too computationally expensive, unless particle collisions are replaced by stochastic forces (Bromley & Kenyon, 2013). Rings are extraordinarily flat systems and therefore are well-suited to existing geophysical shallow-water hydrodynamics models with well-established non-linear advection methods. By adopting a general relationship between pressure and surface density such as a polytropic equation of state, we can modify the shallow-water formula to treat a thin, compressible, self-gravitating, shearing fluid. Previous hydrodynamic simulations of planetary rings have been restricted to axisymmetric flows and therefore have not treated the response to nonaxisymmetric perturbations by moons (Schmidt & Tscharnuter 1999, Latter & Ogilvie 2010). We seek to expand on existing hydrodynamic methods and, by comparing our work with complementary N-body simulations and Cassini observations, confirm the veracity of our results at small scales before eventually moving to a global domain size. We will use non-Newtonian, dynamically variable viscosity to model the viscous transport caused by unresolved self-gravity wakes. Self-gravity will be added to model the dynamics of large-scale structures, such as density waves and edge waves. Support from NASA Outer Planets and Planetary Geology and Geophysics programs is gratefully acknowledged.

  13. Storage ring working group report

    SciTech Connect

    Krinsky, S.

    1997-01-01

    Over the last two decades great progress has been made in the development of storage rings with small transverse emittance. It is now a good time to consider the possibility of achieving very short bunches m storage rings. From the perspective of synchrotron radiation source development, there are at least two motivations for obtaining short electron bunches: (1) the generation of sub- picosecond x-ray pulses and (2) the coherent emission of sub- picosecond pulses of far infrared radiation. A useful short-term goal is the experimental study of bunches with 1 ps rms length both at high ({approx_gt} 1 GeV) and low ({approx_lt} 150 MeV) electron energies. Experiments on 1 ps bunches are now feasible and can yield new insight into the high frequency impedance of storage rings and the associated phenomena which can result in bunch lengthening. Achievement of 1 ps bunches can also be expected to allow the first observation of coherent synchrotron radiation in a storage ring, in the millimeter wavelength regime. A longer-term objective is the realization of 100 fs bunches. Achievement of this goal not only will advance understanding of storage rings but will open up new opportunities in synchrotron radiation based research at both x-ray and far infrared wavelengths. It is now an appropriate time to carry forward theoretical investigations clarifying the fundamental limitations on bunch length, and to devise schemes to minimize it.

  14. Ring Beholds a Delicate Flower

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. A planetary nebula is a shell of material ejected from a dying star. Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.

    The 'ring' is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. The telescope's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit infrared light because they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.

    Download the QuickTime movie for the animated version of this Ring Nebula image.

  15. Archiving of Planetary Ring Data

    NASA Technical Reports Server (NTRS)

    Elliot, James L.

    2001-01-01

    Stellar occultation data provide our only Earth-based means of probing planetary rings at kilometer spatial resolution. The occultation data archive at MIT contains original data and analysis products of stellar occultations by the ring systems of the planets Jupiter, Saturn, Uranus, and Neptune observed by members of the group (and other groups) from 1977 to the present. During this time period, several media have been used to record and store the original and processed data: (1) chart records; (2) printed output, (3) audio reel tape; (4) audio cassette tape; (5) 7-track, 1/2-inch computer tape; (6) 9-track, 1/2-inch computer tape at 800, 1600, and 6250 bpi; (7) NOVA disk platters (2.5 and 5.0 Mbyte); (8) write once optical disks; (9) punched cards; and (10) read-write optical disks. With the rapid change of computer technology over this time period, some of these media have become not only obsolete, but nearly extinct. In particular, it has become nearly impossible to find any facilities that can still read 800 bpi tapes, which contain the only copies of several important data sets for the ring system of Uranus. In particular, we have an extensive ring data collection that includes data sets for the following Uranian ring occultations: U0, U11, U12, U13, U14, U25, U17, and U36.

  16. Ring wormholes via duality rotations

    NASA Astrophysics Data System (ADS)

    Gibbons, Gary W.; Volkov, Mikhail S.

    2016-09-01

    We apply duality rotations and complex transformations to the Schwarzschild metric to obtain wormhole geometries with two asymptotically flat regions connected by a throat. In the simplest case these are the well-known wormholes supported by phantom scalar field. Further duality rotations remove the scalar field to yield less well known vacuum metrics of the oblate Zipoy-Voorhees-Weyl class, which describe ring wormholes. The ring encircles the wormhole throat and can have any radius, whereas its tension is always negative and should be less than -c4 / 4 G. If the tension reaches the maximal value, the geometry becomes exactly flat, but the topology remains non-trivial and corresponds to two copies of Minkowski space glued together along the disk encircled by the ring. The geodesics are straight lines, and those which traverse the ring get to the other universe. The ring therefore literally produces a hole in space. Such wormholes could perhaps be created by negative energies concentrated in toroidal volumes, for example by vacuum fluctuations.

  17. Ring Beholds a Delicate Flower

    NASA Technical Reports Server (NTRS)

    2005-01-01

    NASA's Spitzer Space Telescope finds a delicate flower in the Ring Nebula, as shown in this image. The outer shell of this planetary nebula looks surprisingly similar to the delicate petals of a camellia blossom. A planetary nebula is a shell of material ejected from a dying star. Located about 2,000 light years from Earth in the constellation Lyra, the Ring Nebula is also known as Messier Object 57 and NGC 6720. It is one of the best examples of a planetary nebula and a favorite target of amateur astronomers.

    The 'ring' is a thick cylinder of glowing gas and dust around the doomed star. As the star begins to run out of fuel, its core becomes smaller and hotter, boiling off its outer layers. The telescope's infrared array camera detected this material expelled from the withering star. Previous images of the Ring Nebula taken by visible-light telescopes usually showed just the inner glowing loop of gas around the star. The outer regions are especially prominent in this new image because Spitzer sees the infrared light from hydrogen molecules. The molecules emit infrared light because they have absorbed ultraviolet radiation from the star or have been heated by the wind from the star.

    Download the QuickTime movie for the animated version of this Ring Nebula image.

  18. Ring lasers in precise measurements: A review

    SciTech Connect

    Kozubovskii, V.R.; Privalov, V.E.

    1995-05-01

    Features of the ring laser offer possibilities for various applications. The special features of frequency stabilization of ring lasers are analyzed. The employment of ring lasers in laser spectroscopy and the development of gas analytical devices on their basis are considered. It is shown that ring lasers offer some advantages for linear angular measurements and measurements of parameters of motion. Ways to optimize the parameters of ring lasers are indicated. 180 refs., 21 figs.

  19. Softened-Stainless-Steel O-Rings

    NASA Technical Reports Server (NTRS)

    Marquis, G. A.; Waters, William I.

    1993-01-01

    In fabrication of O-ring of new type, tube of 304 stainless steel bent around mandril into circle and welded closed into ring. Ring annealed in furnace to make it soft and highly ductile. In this condition, used as crushable, deformable O-ring seal. O-ring replacements used in variety of atmospheres and temperatures, relatively inexpensive, fabricated with minimum amount of work, amenable to one-of-a-kind production, reusable, and environmentally benign.

  20. On the formation of ring galaxies

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Ting; Jiang, Ing-Guey

    2011-08-01

    The formation scenario of ring galaxies is addressed in this paper. We focus on the P-type ring galaxies presented in Madore, Nelson & Petrillo (2009), particularly on the axis-symmetric ones. Our simulations show that a ring can form through the collision of disc and dwarf galaxies, and the locations, widths, and density contrasts of the ring are well determined. We find that a ring galaxy such as AM 2302-322 can be produced by this collision scenario.

  1. A widely tunable laser using silica-waveguide ring resonators

    NASA Astrophysics Data System (ADS)

    Yamazaki, Hiroyuki; Takahashi, Morio; Suzuki, Kouichi; Deki, Yukari; Takeuchi, Takeshi; Takaesu, Sekizen; Horie, Mika; Sato, Kenji; Kudo, Koji

    2005-10-01

    A Wide wavelength tunable laser is needed for Wavelength Division Multiplexing (WDM) and Reconfigurable Optical Add/Drop Multiplexing (ROADM) networks, since it realizes flexible network, effectively employing wavelength resources, and inventory cost reduction. Several types currently exist, but they all are difficult to produce; that is, their mass producibility is not high and they have many components. In particular, monolithically integrated wavelength tunable lasers, such as DFB array, and SG(Sampled Grating)-DBR based structures, have been developed. While these lasers have good performance, they require complex InP growth steps and processing. The external cavity lasers also have good performance, but require precise manual assembly and have moving parts. We have proposed novel tunable laser consisting of silica waveguide ring resonator connected directly to semiconductor optical amplifier. This laser structure has several advantages, such as a simple laser structure suitable for mass-production and high reliability due to having a stable thermal optic phase shifter and no moving parts. This paper gives recent progress in waveguide ring resonator based tunable laser. Low loss and high performance silica waveguide ring resonator, which was suitable for tunable laser, was successfully fabricated using high index contrast SiON core. Double-ring resonators successfully attained 45-nm and 160-nm wavelength tuning operations, which was the largest wavelength tuning range in a tunable laser with no mechanical moving parts reported to date. Triple-ring resonator demonstrated stable full L-band tuning operations with 50-GHz wavelength spacing. We believe that silica waveguide ring resonator based tunable laser is very suitable for not only mass production, but also widely wavelength tuning and stable single mode operations.

  2. Cassini FUV Spectral Properties of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Bradley, Eric Todd; Colwell, J. E.; Esposito, L. W.; Cuzzi, J. N.; Tollerud, H.; Chambers, L.

    2009-09-01

    Spectra taken by the Cassin Ultraviolet Imaging Spectrograph (UVIS) of Saturn's C ring, B ring, Cassini Division, and A ring have been analyzed in order to characterize ring particle regolith properties, water ice abundance in the rings, and macroscopic scattering properties. Spectra of the normalized reflectance (I/F) in all four regions show a characteristic water ice absorption feature near 1650 Å. Using only the spectral shape of the water ice absorption feature, a modified Hapke model and Shkuratov model were used to determine the asymmetry parameter and photon mean path length for the regolith associated with ice grains on ring particles. Both models assume multiple scattering between regolith grains on a given ring particle. Retrieved values of the single scattering asymmetry parameter show the regolith grains to be highly backscattering in the FUV spectral regime. Retrieved values of the photon mean path length show a strong correlation with ring brightness in the C ring but are anti-correlated with ring brightness from the inner B ring through the outer A ring. The UV slope of 1800/1500 Å (reflectance outside the water absorption ratioed to that inside the absorption band) shows that the fractional abundance of surface water ice is largest in the outer B ring and decreases by over a factor of 2 across the inner C ring. Under a single scattering assumption, we are analyzing the data to look at the ring particle phase function and albedo for measurements over a range of phase angles and will present those results.

  3. CMB lensing and giant rings

    SciTech Connect

    Rathaus, Ben; Itzhaki, Nissan E-mail: ben.rathaus@gmail.com

    2012-05-01

    We study the CMB lensing signature of a pre-inationary particle (PIP), assuming it is responsible for the giant rings anomaly that was found recently in the WMAP data. Simulating Planck-like data we find that generically the CMB lensing signal to noise ratio associated with such a PIP is quite small and it would be difficult to cross correlate the temperature giant rings with the CMB lensing signal. However, if the pre-inationary particle is also responsible for the bulk flow measured from the local large scale structure, which happens to point roughly at the same direction as the giant rings, then the CMB lensing signal to noise ratio is fairly significant.

  4. Traversable wormholes: The Roman ring

    SciTech Connect

    Visser, M.

    1997-04-01

    In this Brief Report I introduce yet another class of geometries for which semiclassical chronology protection theorems are of dubious physical reliability. I consider a {ital {open_quotes}Roman ring{close_quotes}} of traversable wormholes, wherein a number of wormholes are arranged in a ring in such a manner that no subset of wormholes is near chronology violation, though the combined system can be arbitrarily close to chronology violation. I show that (with enough wormholes in the ring) the gravitational vacuum polarization (the expectation value of the quantum stress-energy tensor) can be made arbitrarily small. In particular, the back reaction can be kept arbitrarily small all the way to the {open_quotes}reliability horizon,{close_quotes} so that semiclassical quantum gravity becomes unreliable before the gravitational back reaction becomes large. {copyright} {ital 1997} {ital The American Physical Society}

  5. Remote Sensing of Dipole Rings

    NASA Technical Reports Server (NTRS)

    Hooker, Stanford B.; Mied, Richard P.; Brown, James W.; Kirwan, A. D., Jr.

    1997-01-01

    Historical satellite-derived sea surface temperature (SST) data are reanalyzed with a zebra color palette and a thermal separatrix method. The new results from this reanalysis are as follows: (a) Thirteen observational sequences of six rings from the Gulf Stream and the Brazil Current, which have historically been interpreted as solitary vortices or monopoles are shown to have a dipolar character; (b) some of these dipole rings have been observed in the open ocean, thereby eliminating the possibility that they are sustained by topographic interactions with the continental slope; (c) whether interacting with other features or evolving as isolated circulations, dipoles are seen to rotate within a relatively narrow range of approximately 4-8 deg/day (interacting) and 10-11 deg/day (isolated); and (d) feature tracking delineates energetic fluid in both vortices and eliminates the possibility of interpreting dipole rings as transient features produced by active monopoles and patches of entrained fluid.

  6. Ring Vaccination and Smallpox Control

    PubMed Central

    van den Hof, Susan; Wallinga, Jacco; van Wijngaarden, Jan

    2004-01-01

    We present a stochastic model for the spread of smallpox after a small number of index cases are introduced into a susceptible population. The model describes a branching process for the spread of the infection and the effects of intervention measures. We discuss scenarios in which ring vaccination of direct contacts of infected persons is sufficient to contain an epidemic. Ring vaccination can be successful if infectious cases are rapidly diagnosed. However, because of the inherent stochastic nature of epidemic outbreaks, both the size and duration of contained outbreaks are highly variable. Intervention requirements depend on the basic reproduction number R0, for which different estimates exist. When faced with the decision of whether to rely on ring vaccination, the public health community should be aware that an epidemic might take time to subside even for an eventually successful intervention strategy. PMID:15200816

  7. The Sound of Science: Comparison of Cassini Ring Crossings

    NASA Image and Video Library

    2017-05-01

    The sounds and spectrograms in these two videos represent data collected by the Radio and Plasma Wave Science, or RPWS, instrument on NASA's Cassini spacecraft, as it crossed the plane of Saturn's rings on two separate orbits. As tiny, dust-sized particles strike Cassini and the three 33-foot-long (10-meter-long), RPWS antennas, the particles are vaporized into tiny clouds of plasma, or electrically excited gas. These tiny explosions make a small electrical signal (a voltage impulse) that RPWS can detect. Researchers on the RPWS team convert the data into visible and audio formats, like those seen here, for analysis. Ring particle hits sound like pops and cracks in the audio. The first video (top image in the montage) was made using RPWS data from a ring plane crossing on Dec. 18, 2016, when the spacecraft passed through the faint, dusty Janus-Epimetheus ring (see PIA08328 for an image that features this ring). This was during Cassini's 253rd orbit of Saturn, known as Rev 253. As is typical for this sort of ring crossing, the number of audible pops and cracks rises to a maximum around the time of a ring crossing and trails off afterward. The peak of the ring density is obvious in the colored display at the red spike. The second video (bottom image in the montage) was made using data RPWS collected as Cassini made the first dive through the gap between Saturn and its rings as part of the mission's Grand Finale, on April 26, 2017. Very few pops and cracks are audible in this data at all. In comparing the two data sets, it is apparent that while Cassini detected many ring-particles striking Cassini when passing through the Janus-Epimetheus ring, the first Grand Finale crossing -- in stark contrast -- was nearly particle free. The unexpected finding that the gap is so empty is a new mystery that scientists are eager to understand. On April 26, 2017, Cassini dove through the previously unexplored ring-planet gap at speeds approaching 75,000 mph (121,000 kph), using its

  8. Radar Data Explanation via Superdiamagnetic Model of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Girich, S. V.; Pospelov, A. Yu.; Tchernyi, V. V.; CITO MVD Collaboration; GPI RAS Team; MSIEM LMIS Team

    1998-09-01

    range 10 mm - 10 cm has the same behavior as those for the surface resistance of superconductors. 3. Frequency anomalies in the thermal radiation of Saturn's rings in the spectrum range 100 mm - 1 cm Thermal radiation of the rings of Saturn on the wavelengths in the range 10 mm - 1 cm also has been measured. The measured brightness temperatures on short waves are less than true brightness temperature of rings, and on longer waves the rings look much colder than in the case when the radiation corresponds to their physical temperature. On the wavelengths 100 mm - 1 mm brightness temperature of the ring sharply falls to the meanings less than those ones characteristic of an absolutely black body. On the wavelengths longer than 1 cm a ring behaves as the diffusion screen, reflecting planetary and cold space radiation. Under the superconducting condition the electrons do not interact with a crystal lattice and do not exchange energy with it, therefore they cannot transfer heat from one part of a body into another one. Hence, when substance passes into superconducting condition, its heat conductivity is lowered. Keywords: planetary rings; radiation, reflection and absorption; superdiamagnetic liquid; superconducting particles.

  9. Formation and evolution of concentric vortex rings

    NASA Astrophysics Data System (ADS)

    Sadri, Vahid

    The formation and interactions of concentric vortex rings are studied experimentally and computationally using a concentric piston-cylinder geometry to generate concentric vortex rings in water at a maximum jet Reynolds number of 2000. The effects of cylinder gap ratio, DeltaR/R, and jet stroke length-to-gap ratio, L/DeltaR, on the evolution of the flow were investigated. For the experimental study, the jet pulses were generated using piston stroke to gap size ratios (?R/R) in the range 0.2 to 0.05, and L/DeltaR in the range 1-20, for a trapezoidal piston velocity program. Digital Particle Image Velocimetry (DPIV) was used to measure concentric vortex ring position, vorticity, and velocity. Additional experiments were conducted using dye visualizations to reveal the spatial structure of the instability for concentric vortex rings. For the computational study, the flow was simulated at a jet Reynolds number of 1,000 (based on DeltaR and the jet velocity), L/DeltaR in the range 1-20, and DeltaR/R in the range 0.01-0.25. The large L/DeltaR and small DeltaR/R cases were included, in part, to investigate the pinch-off of axisymmetric vortex pairs generated by flow between concentric cylinders with radial separation DeltaR for comparison with planar vortex dipole behavior. Five characteristic flow evolution patterns were observed and classified based on L/DeltaR and DeltaR/R for concentric vortex ring behavior. The results showed that the relative position, relative strength, and radii of the vortex rings during and soon after formation played a prominent role in the evolution of the trajectories of their vorticity centroids at the later time. The conditions on relative strength of the vortices necessary for them to travel together as a pair following formation were studied and factors affecting differences in vortex circulation following formation were investigated. In addition to the characteristics of the primary vortices, the stopping vortices had a strong influence

  10. Chromosome 18 replaced by two ring chromosomes of chromosome 18 origin.

    PubMed

    Miller, K; Pabst, B; Ritter, H; Nürnberg, P; Siebert, R; Schmidtke, J; Arslan-Kirchner, M

    2003-04-01

    We here describe the first example of the replacement of an autosome by two ring chromosomes originating from the missing chromosome, presented in a patient with a single chromosome 18 and two additional ring chromosomes. Detailed fluorescence in situ hybridization (FISH) analysis revealed the chromosome 18 origin of both ring chromosomes and characterized the small and the large ring chromosome as derivatives of the short and long arm of chromosome 18, respectively. The loss of subtelomeric regions of the short and the long arm of chromosome 18 in the ring chromosomes was confirmed by FISH studies. Molecular studies showed the exclusive presence of the paternal alleles for microsatellite markers located distal to the short and long arm loci D18S843 and D18S474, respectively. This indicates the maternal origin of both rings and provides evidence for substantial deletions of the distal parts of both arms of chromosome 18 in the ring chromosomes. The dysmorphic features of the patient can be explained by these deletions in both chromosome arms, as the clinical findings partly overlap with observations in 18p- and 18q-syndrome and are similar to some cases of ring chromosome 18. Centromere misdivision is suggested as one mechanism involved in the formation of the ring chromosomes.

  11. Physics of Jupiter's Gossamer Rings

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas P.; Krueger, H.

    2008-05-01

    Thebe's gossamer ring, the outermost and faintest of Jupiter's rings, extends outward by at least half a jovian radius from its source satellite while maintaining a constant vertical thickness. This structure is created by an electromagnetic perturbation known as a shadow resonance (Hamilton 2003, DPS meeting #35, #11.09). A shadow resonance arises from the abrupt shutoff of photoelectric charging when a dust particle enters Jupiter's shadow which, in turn, affects the strength of the electromagnetic perturbation from the planet's intense magnetic field. The result is a coupled oscillation between a particle's orbital eccentricity and its semimajor axis. Ring material spreads outward from Thebe while maintaining its vertical thickness just as observed by Galileo imaging. In addition to cameras, the Galileo spacecraft was also equipped with dust and plasma detectors. The spacecraft made two passes through the ring and its dust detector found that 1) dust fluxes drop immediately interior to Thebe's orbit, 2) some grains have inclinations in excess of 20 degrees and 3) submicron particles are present in the Amalthea ring in much greater numbers than in the Thebe ring. These findings can all be explained in the context of our shadow resonance model: the inner boundary is a direct consequence of the conservation of the Electromagnetic Jacobi Constant, the high inclinations are forced by a vertical version of the shadow resonance, and the excess submicron particles are a consequence of the weakening of electromagnetic forces in the vicinity of synchronous orbit. In this talk, we will present the data sets as well as detailed numerical simulations that back up these claims.

  12. 20 - 50 GeV muon storage rings for a neutrino factory

    SciTech Connect

    Rees, G.H.; Johnstone, C.; Meot, F.; /DAPNIA, Saclay

    2006-07-01

    Muon decay rings are under study as part of an International Scoping Study (ISS) for a future Neutrino Factory. Both isosceles triangle- and racetrack-shaped rings are being considered for a 20 GeV muon energy, but with upgrade potentials of 40 or 50 GeV. Both rings are designed with long straights to optimize directional muon decay. The neutrinos from muon decay pass to one or two distant detectors; the racetrack ring has one very long production straight aligned with one detector while the triangular ring has two straights which can be aligned with two detectors. Decay ring specifications and lattice studies are the primary topic of this paper. Injection, collimation, and the RF system are covered in a second contribution to these proceedings.

  13. Physical processes in Jupiter's ring - Clues to its origin by Jove

    NASA Technical Reports Server (NTRS)

    Burns, J. A.; Showalter, M. R.; Cuzzi, J. N.; Pollack, J. B.

    1980-01-01

    It is shown that many of the observed properties of the Jovian ring can be explained by the presence of numerious small and unseen parent bodies, or 'mooms', residing within the ring; whose radii are less than 1 km. The small visible ring grains, which are destroyed in short times by sputtering and meteoroid erosion, are derived from these parent bodies largely through meteoroid impacts, and partly from Io's dust. Substantial orbit modification results from plasma drag, and the charge carried by the grains will influence their dynamics and may modify their shapes. It is concluded that the processes discussed, though present in other planetary ring systems, may be highlighted in Jupiter's ring because of its low optical depth and the small size of some of its particles. It is suggested that hidden reservoirs similar to the Jovian 'mooms' proposed may be present in the rings of Saturn and Uranus.

  14. Hawking radiation from black rings

    SciTech Connect

    Miyamoto, Umpei; Murata, Keiju

    2008-01-15

    We calculate the quantum radiation from the 5-dimensional charged rotating black rings by demanding the radiation eliminate the possible anomalies on the horizons. It is shown that the temperature, energy flux, and angular-momentum flux exactly coincide with those of the Hawking radiation. The black rings considered in this paper contain the Myers-Perry black hole as a limit, and the quantum radiation for this black hole, obtained in the literature, is recovered in the limit. The results support the picture that the Hawking radiation can be regarded as the anomaly eliminator on horizons and suggest its general applicability to the higher-dimensional black holes discovered recently.

  15. Damping ring designs and issues

    SciTech Connect

    Wolski, Andrzej; Decking, Winfried

    2003-05-12

    The luminosity performance of a future linear collider (LC) will depend critically on the performance of the damping rings. The design luminosities of the current LC proposals require rings with very short damping times, large acceptance, low equilibrium emittance and high beam intensity. We discuss the design strategies for lattices achieving the goals of dynamical stability, examine the challenges for alignment and coupling correction, and consider a variety of collective effects that threaten to limit beam quality. We put the design goals in context by referring to the experience of operating facilities, and outline the further research and development that is needed.

  16. Ring Around the Sun

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Our 'constant' sun is really more like a spherical sea of incredibly hot plasma, changing all the time. Astronomers like to keep a good eye on it, so no dramatic change goes by unnoticed. One amazing occurrence happened on Dec 7, 2007 and was seen by one of the two STEREO satellites. STEREO, as you recall, consists of a pair of satellites which observe the sun from different angles and allow astronomers to get a ŗ-D' view of the solar atmosphere and solar outflows. On December 7 one of the STEREO satellites captured a view (in the extreme ultraviolet part of the electromagnetic spectrum) of a Coronal Mass Ejection that released a huge amount of energy into the solar atmosphere, and a huge amount of matter into interplanetary space. A sort of atmospheric 'sunquake'. One result of this 'sunquake' was the production of a giant wave rippling through almost the entire solar atmosphere. The image above shows a snapshot of this unbelievable wave, slightly enhanced for viewability. Don't miss the movie. What damps the wave?

  17. A Crack in the C Ring?

    NASA Astrophysics Data System (ADS)

    Nicholson, Philip D.; Hedman, M. M.; Cassini VIMS Team

    2010-10-01

    The most prominent wavelike feature in Saturn's C ring, at a radius of 77520 - 77600 km, was identified by Rosen & Lissauer (1988; Science 241, 690) in Voyager radio occultation data as a vertical or bending wave driven at the Titan -1:0 nodal resonance. At such a resonance, the nodal regression rate of ring particles approximately matches the negative of the satellite's mean motion. Unlike other bending waves, this wave propagates radially outwards due to its negative pattern speed; its prominence in the Voyager profile was attributed to the very low elevation angle of 6 degrees, which amplified the effect of subtle vertical corrugations. However, the same wave appears in twenty stellar occultation profiles of the C ring obtained with the Cassini VIMS instrument at elevation angles as high as 62 degrees, casting some doubt on its identification as a bending wave. Also troubling is an apparently empty gap in the inner part of the Voyager wave profile, which also appears in about one-half of the VIMS profiles. When these data are organized by their position with respect to the predicted spiral pattern, the gap is seen to extend over 180 degrees in longitude, with varying width. A simple model which can account for these observations consists of a very narrow (< 1 km), continuous gap, one of whose edges is inclined with respect to the other by a few km. This is comparable to the amplitude of the bending wave inferred by Rosen & Lissauer. The gap is located only 14 km exterior to the nominal location of the -1:0 resonance, suggesting that the vertical displacement of its edge is resonantly forced. We acknowledge helpful discussions with R.G. French of the Cassini RSS team, and support from the Cassini/Huygens project.

  18. Uranus' Rings: Leading up to RPX

    NASA Astrophysics Data System (ADS)

    de Pater, I.; Showalter, M.; Hammel, H.; Gibbard, S.; Lissauer, J.

    We summarize recent HST and Keck observations of the uranian ring system, taken over the past years while the viewing geometry is changing. Some highlights of our campaign to date include: i) Detection of a ring system outside of Uranus main ring system by HST (Showalter and Lissauer, Science 311, p.973, 2006), followed by color information from Keck (de Pater et al, Science 312, p.92, 2006). This system consists of two rings. The inner ring, U2, is red and relatively narrow like Saturn's G ring, while the outer ring, U1, is much broader in extent and very blue, like Saturn's E ring. Just like Enceladus is located within the E ring, moon Mab is inside U1. Saturn's E ring is most likely produced by geyser activity on Enceladus. Mab, being over 20 times smaller, is unlikely to be geologically active. However, being this small, its size is optimal to produce a ring via meteorite sputtering. ii) Detection of a ring interior to the main ring system, which might be ring 1986U2R, discovered by Voyager, though its extent and location is different from the Voyager ring. iii) Dust sheets in between the main ring. These may be similar to the dust sheets seen by Voyager in forward scattered light, yet our observations indicate large changes from the Voyager era iv) New moons were detected by HST. The orbits of some of these moons appear to be somewhat erratic. The color of moon Mab appears to be more similar to that of the large outer moons than the small inner moons. Earth will cross Uranus' ring plane three times in 2007-2008 (2 May, 16 Aug. 2007, 20 Feb. 2008), and the Sun will cross it once (7 Dec. 2007). At these times optically thin dusty rings will brighten considerably, making this period an ideal time to study Uranus' outer ring system. Between the May and August crossings, as well as between December and February, the Earth and Sun are on opposite sides of the rings, so that any optically thick rings will essentially be invisible. This allows phenomena normally

  19. Transparent Optical Protection Ring Architectures and Applications

    NASA Astrophysics Data System (ADS)

    Li, Ming-Jun; Soulliere, Mark J.; Tebben, Daniel J.; Nederlof, Leo; Vaughn, Mark D.; Wagner, Richard E.

    2005-10-01

    This paper reviews recent progress in optical protection rings with the focus on transparent optical protection rings. Different optical protection ring architectures, such as dedicated and shared protection rings, in both the optical-channel (OCh) layer and the optical multiplex section (OMS) layer, are described. In particular, OCh shared protection rings (OChSPRINGs) are discussed in detail including node-architecture designs, ring protocols, triggers, and messaging channels. Feasibility studies and experimental results from Corning Inc. and other companies are reviewed. The paper also discusses how protection-switching times scale with number of nodes and number of wavelengths, and shows examples of applications using the scaling rules for practical optical networks such as metro, regional, and long-haul ring networks. The cost benefits of transparent optical protection rings are analyzed using a typical metro network. Finally, the paper discusses remaining issues and future developments in the optical protection ring area.

  20. INVITED TALK: Dynamics Of Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    2011-04-01

    Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We will review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We will then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk), and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally-confined arcs both at Saturn, Jupiter, and Neptune. Finally, every known ring system includes a substantial component of diffuse dusty rings.

  1. Dependency of the regio- and stereoselectivity of intramolecular, ring-closing glycosylations upon the ring size

    PubMed Central

    Claude, Patrick; Lehmann, Christian

    2011-01-01

    Summary Phenyl 3,4,6-tri-O-benzyl-2-O-(3-carboxypropionyl)-1-thio-β-D-galactopyranoside (1) was condensed via its pentafluorophenyl ester 2 with 5-aminopentyl (4a), 4-aminobutyl (4b), 3-aminopropyl (4c) and 2-aminoethyl 4,6-O-benzylidene-β-D-glucopyranoside (4d), prepared from the corresponding N-Cbz protected glucosides 3a–d, to give the corresponding 2-[3-(alkylcarbamoyl)propionyl] tethered saccharides 5a–d. Intramolecular, ring closing glycosylation of the saccharides with NIS and TMSOTf afforded the tethered β(1→3) linked disaccharides 6a–c, the α(1→3) linked disaccharides 7a–d and the α(1→2) linked disaccharide 8d in ratios depending upon the ring size formed during glycosylation. No β(1→2) linked disaccharides were formed. Molecular modeling of saccharides 6–8 revealed that a strong aromatic stacking interaction between the aromatic parts of the benzyl and benzylidene protecting groups in the galactosyl and glucosyl moieties was mainly responsible for the observed regioselectivity and anomeric selectivity of the ring-closing glycosylation step. PMID:22238538

  2. Initial Cassini Ultraviolet Observations of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Colwell, J. E.

    2004-12-01

    The first ring occultation to be observed by Cassini is of the star Xi Ceti on October 6-7, 2004, from a distance of 6.22 million km. The Ultraviolet Imaging Spectrograph (UVIS) includes a High Speed Photometer with a bandpass of ˜110-190 nm that has an integration period of 8 msec for this observation. The Fresnel zone at this distance is ˜40 m, and the speed of the occultation gives a radial sampling interval of 5-8 m. The occultation covers the C ring, Cassini Division, A ring, and F ring. The occultation is particularly well-suited for the low to intermediate optical depth regions of the C and F rings and the Cassini Division, and will have lower effective resolution in the higher optical depth regions of the A ring. The Xi Ceti occultation is by far the most distant that Cassini will observe. Ultraviolet spectral reflectance observations were also made at Saturn Orbit Insertion on July 1, 2004, providing the highest spatial resolution UV reflectance of the rings, with a 150 km effective resolution. Spectral variations are seen between the C, B, and A rings and the Cassini Division indicating varying amounts of dark material mixed in with water ice in the rings. The A ring is significantly brighter than the B and C rings, and its brightness increases with increasing radial distance. Meteoroid impacts into the rings darken the rings through the addition of silicates and carbonaceous material. Observed fluctuations in the UV brightness at length scales of less than 3000 km can be explained by impact fragmentation of moonlets or large ring particles in the rings. These fragmentation events expose relatively pure ice from the interior of the moonlet, leading to a local brightening of the ring which is gradually reduced and mixed with the surrounding ring material as the meteoroid bombardment continues. We will present our initial findings on ring structure, UV brightness, and particle sizes.

  3. Ring artifacts correction in compressed sensing tomographic reconstruction

    PubMed Central

    Paleo, Pierre; Mirone, Alessandro

    2015-01-01

    Ring artifacts are a very common problem in tomographic reconstruction, and numerous methods exist to either pre-process the sinogram or correct the reconstructed slice. A novel approach to perform the correction as part of the reconstruction process is presented. It is shown that for iterative techniques, which amount to optimizing an objective function, the ring artifacts correction can be easily integrated in the formalism, enabling simultaneous slice reconstruction and ring artifacts correction. This method is tested and compared with mainstream correction techniques for both simulated and experimental data. Results show that the correction is efficient, especially for undersampled datasets. This technique is included in the PyHST2 code which is used at the European Synchrotron Radiation Facility for tomographic reconstruction. PMID:26289279

  4. Thomson’s ring experiment with resonant LC circuit

    NASA Astrophysics Data System (ADS)

    Haidar, Sajjad

    2016-01-01

    Thomson’s jumping ring experiment is conducted using a low voltage (24 V) electronic circuit. A coil (L) is connected with a capacitor (C) in parallel and is driven at its resonant frequency to obtain a high current in the coil. A circuit sends current pulses to the LC tank circuit at around its resonant frequency. The oscillating current in the coil induces a voltage in a copper-loop on top of it. The induced current interacts with the radial part of the coil-magnetic field; the resulting force levitates the loop. In a separate coil, a ferrite core and a copper ring are used to demonstrate the jumping-ring effect. The levitation and the jumping effect can be controlled by changing the duty cycle and frequency. In this report simple formulae and approximations are used to calculate the levitating force on the loop.

  5. Dimensional crossover of the dephasing time in disordered mesoscopic rings

    NASA Astrophysics Data System (ADS)

    Treiber, M.; Yevtushenko, O. M.; Marquardt, F.; von Delft, J.; Lerner, I. V.

    2009-11-01

    We study dephasing by electron interactions in a small disordered quasi-one-dimensional (1D) ring weakly coupled to leads. We use an influence functional for quantum Nyquist noise to describe the crossover for the dephasing time τφ(T) from diffusive or ergodic 1D (τφ-1∝T2/3,T1) to zero-dimensional (0D) behavior (τφ-1∝T2) as T drops below the Thouless energy. The crossover to 0D, predicted earlier for two-dimensional and three-dimensional systems, has so far eluded experimental observation. The ring geometry holds promise of meeting this long-standing challenge, since the crossover manifests itself not only in the smooth part of the magnetoconductivity but also in the amplitude of Altshuler-Aronov-Spivak oscillations. This allows signatures of dephasing in the ring to be cleanly extracted by filtering out those of the leads.

  6. The EMMA Main Ring Lattice.

    SciTech Connect

    Berg,J.S.

    2008-02-21

    I give a brief introduction to the purpose and goals of the EMMA experiment and describe how they will impact the design of the main EMMA ring. I then describe the mathematical model that is used to describe the EMMA lattice. Finally, I show how the different lattice configurations were obtained and list their parameters.

  7. Conical O-ring seal

    DOEpatents

    Chalfant, G.G. Jr.

    A shipping container for radioactive or other hazardous materials has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  8. Stirring properties of vortex rings

    NASA Astrophysics Data System (ADS)

    Auerbach, David

    1991-05-01

    Ring vortex evolution, from the initial roll-up phase through to the final turbulent phase, was experimentally studied to see the dependence of its stirring properties on both the initial (accelerating, constant, decelerating, slow, fast) piston motion as well as on the boundary (tube/hole geometry) conditions. Stirring between fluid initially upstream and that initially downstream of the nozzle plane is done more by convective entrainment at the beginning (roll-up and contraction phases), by diffusive entrainment during the laminar and wavy phases, and by mixed entrainment and ejection during the transition to turbulence and the turbulent phase itself. During vortex roll-up, it was found that tubes eject shorter streaklines than do holes, and that there is less Re dependence for this for tubes than for holes. During the contraction phase, entrainment ends, save for minimal entrainment due to axial inflow into the ring from along the cores of Goertler-type vortices. Generally, the rate of fluid ejected is largest during the transition from the wavy to the turbulent state. As far as the stability of the vortices is concerned, rings generated at holes are less stable than those generated at tubes. During the final turbulent phase, rings not only entrain fluid but eject it periodically into the wake: Between two and four hairpin vortices are generated and laid off in the wake during each ejection. The frequency at which such ejections takes place scales as a Strouhal number that takes on values of between 2 and 4.

  9. Barred Ring Galaxy NGC 1291

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image left and visual image right from NASA Galaxy Evolution Explorer is of the barred ring galaxy NGC 1291. The VIS image is dominated by the inner disk and bar. The UV image is dominated by the low surface brightness outer arms.

  10. Conical O-ring seal

    DOEpatents

    Chalfant, Jr., Gordon G.

    1984-01-01

    A shipping container for radioactive or other hazardous materials which has a conical-shaped closure containing grooves in the conical surface thereof and an O-ring seal incorporated in each of such grooves. The closure and seal provide a much stronger, tighter and compact containment than with a conventional flanged joint.

  11. On the vortex ring state

    NASA Astrophysics Data System (ADS)

    Green, Richard; Gillies, E.; Giuni, M.; Hislop, J.; Savas, Omer

    2014-11-01

    The investigation considers the vortex ring state, a phenomenon normally associated with the collapse of a trailing, helical vortex wake into a unstable vortex ring, and is a problem encountered when a helicopter rotor descends into its own wake. A series of wind tunnel and towing tank experiments on rotor systems have been performed, and a comparison is then made with the behaviour of a specially designed open core, annular jet system that generates a mean flow velocity profile similar to that observed below a rotor. In experimentally simulated descents the jet system forms flow patterns that are topologically similar to the vortex ring state of a rotor system. Furthermore the dynamic behaviour of the flow shares many of the important characteristics of the rotor flow. This result suggests that the phenomenon of the vortex ring state of a rotor wake is decoupled from the detailed vortex dynamics of the helical vortex filaments themselves. The presentation will describe the principle behind the investigation, the details of the annular jet system and the results gained using PIV and flow visualisation of the wake and jet systems.

  12. RHIC Ring Element Nomenclature System

    SciTech Connect

    Hahn, H.; Rufer, C.; Sondericker, J.

    1990-10-11

    A technical note was published by Hahn, in March 1985, that presented a nomenclature system which identified RHIC main magnets and their position in the ring structure. A revised nomenclature system is described in this technical note which supersedes the earlier version. This present designation completes the 1985 note and has been enlarged to take into account practical considerations like machine installation and operation.

  13. Looking for rings and things

    NASA Astrophysics Data System (ADS)

    Kenworthy, Matthew

    2017-04-01

    It's not often that an astronomical object gets its own dedicated observatory, but as the planet Beta Pictoris b moves in front of its host star, its every move will be watched by bRing, eager to discover more about the planet's Hill sphere, explains Matthew Kenworthy.

  14. Baroclinic Structure of Oceanic Rings

    NASA Astrophysics Data System (ADS)

    Zhang, L.; Sun, C.

    One of the most important analytical solutions to the two dimensional incompressible flow is circular Rankin vortex that has a solid-body core and an approximately irrotational far field. For an f-plane rotating flow, Ingersoll (1969) presented a closed-form ring solution superposed with a zonal flow. So far most studies have been concerned with two dimensional and barotropic situations.

  15. Cavity-locked ring down spectroscopy

    DOEpatents

    Zare, Richard N.; Paldus, Barbara A.; Harb, Charles C.; Spence, Thomas

    2000-01-01

    Distinct locking and sampling light beams are used in a cavity ring-down spectroscopy (CRDS) system to perform multiple ring-down measurements while the laser and ring-down cavity are continuously locked. The sampling and locking light beams have different frequencies, to ensure that the sampling and locking light are decoupled within the cavity. Preferably, the ring-down cavity is ring-shaped, the sampling light is s-polarized, and the locking light is p-polarized. Transmitted sampling light is used for ring-down measurements, while reflected locking light is used for locking in a Pound-Drever scheme.

  16. The formation of Jupiter's faint rings

    PubMed

    Burns; Showalter; Hamilton; Nicholson; de Pater I; Ockert-Bell; Thomas

    1999-05-14

    Observations by the Galileo spacecraft and the Keck telescope showed that Jupiter's outermost (gossamer) ring is actually two rings circumscribed by the orbits of the small satellites Amalthea and Thebe. The gossamer rings' unique morphology-especially the rectangular end profiles at the satellite's orbit and the enhanced intensities along the top and bottom edges of the rings-can be explained by collisional ejecta lost from the inclined satellites. The ejecta evolves inward under Poynting-Robertson drag. This mechanism may also explain the origin of Jupiter's main ring and suggests that faint rings may accompany all small inner satellites of the other jovian planets.

  17. High-Speed Ring Bus

    NASA Technical Reports Server (NTRS)

    Wysocky, Terry; Kopf, Edward, Jr.; Katanyoutananti, Sunant; Steiner, Carl; Balian, Harry

    2010-01-01

    The high-speed ring bus at the Jet Propulsion Laboratory (JPL) allows for future growth trends in spacecraft seen with future scientific missions. This innovation constitutes an enhancement of the 1393 bus as documented in the Institute of Electrical and Electronics Engineers (IEEE) 1393-1999 standard for a spaceborne fiber-optic data bus. It allows for high-bandwidth and time synchronization of all nodes on the ring. The JPL ring bus allows for interconnection of active units with autonomous operation and increased fault handling at high bandwidths. It minimizes the flight software interface with an intelligent physical layer design that has few states to manage as well as simplified testability. The design will soon be documented in the AS-1393 standard (Serial Hi-Rel Ring Network for Aerospace Applications). The framework is designed for "Class A" spacecraft operation and provides redundant data paths. It is based on "fault containment regions" and "redundant functional regions (RFR)" and has a method for allocating cables that completely supports the redundancy in spacecraft design, allowing for a complete RFR to fail. This design reduces the mass of the bus by incorporating both the Control Unit and the Data Unit in the same hardware. The standard uses ATM (asynchronous transfer mode) packets, standardized by ITU-T, ANSI, ETSI, and the ATM Forum. The IEEE-1393 standard uses the UNI form of the packet and provides no protection for the data portion of the cell. The JPL design adds optional formatting to this data portion. This design extends fault protection beyond that of the interconnect. This includes adding protection to the data portion that is contained within the Bus Interface Units (BIUs) and by adding to the signal interface between the Data Host and the JPL 1393 Ring Bus. Data transfer on the ring bus does not involve a master or initiator. Following bus protocol, any BIU may transmit data on the ring whenever it has data received from its host. There

  18. Targeted flyby images of propellers in Saturn's A ring

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.; Baker, Emily J.; the Cassini ISS Team

    2017-06-01

    As part of its two-part end-of-mission maneuvers, the Cassini has targeted three "propeller moons" for close-range flybys, obtaining images that greatly improve on all previous images in terms of resolution and detailed structure. Propeller moons are ~1 km in size and are embedded in the disk of Saturn's A ring (Tiscareno et al. 2010, ApJL). Unlike the moons Pan and Daphnis, propeller moons have insufficient mass to carve out a fully circumferential gap; instead, we see a propeller-shaped disturbance around the moon (which itself is unseen) as the moon's attempted gap is filled back in, due to the dynamical viscosity of the ring particles.The Cassini Imaging Science Subsystem (ISS) has obtained images of the propeller moon "Santos-Dumont" on both the lit and unlit sides of the rings, and of "Earhart" on the lit side. As of this writing, a final targeted flyby of "Bleriot" on the unlit side of the rings has yet to take place. The resolution of these images is at least 3x to 4x better than those of nearly all previous propeller images, and at least 2x better than those of a small handful of the best previous propeller images.We will present maps of of the propeller structures, with enhanced ability to convert brightness to optical depth and surface density due to information from both the lit and unlit sides of the rings. The images contain more complex structure than is predicted by simple models, which we will describe, and for which we will comment on likely explanations. The central moonlet of each propeller (which has never been seen) should be a couple of pixels across, but we cannot confirm whether they are seen in these images or whether they are obscured by stirred-up ring material.

  19. Wireless optics protection of fiber via SONET ring closure

    NASA Astrophysics Data System (ADS)

    Mullen, Ruth Ann; Celmer, Ken T.; Foster, Michael; Wooten, Jimmie; Miller, Jared; Kean, John C.; Carter, Doug; Kefauver, Michael; Singh, Bhupendra; Achour, Maha; Willebrand, Heinz A.

    2001-02-01

    12 A free-space laser link closes an otherwise all-fiber SONET ring, demonstrating for the first time the feasibility of using wireless optics as a back-up to fiber in an application demanding the highest levels of statistical availability and sub-50-ms protection-restoral times. This experiment demonstrates that protocol-transparent wireless optical links can be readily internetworked with industry- standard fiber-based protection protocols to achieve SONET restoral times in the event of a fiber cut. By using the wireless optics as a back-up to fiber rather than as the primary link, end-users are normally protected from the unavoidable burst errors and outages that can arise on a wireless optical link in the event of anomalously poor atmospheric visibility or unanticipated line-of-sight obstructions. While an all-fiber SONET ring operating over physically diverse paths is generally preferred, hybrid fiber/air rings operating over physically-diverse paths (fiber as one path and air as the other) will easily meet or exceed existing Bellcore availability standards for SONET rings. The hybrid part-fiber, part-air ring advantageously protects customers from fiber cuts (a.k.a. `backhoe fade') and may be preferable to over service via either an unprotected fiber spur or over a `collapsed' fiber ring made up of fiber segments sharing a common conduit. The experiment is performed at an OC-12 (622 Mbps) data rate in a point-to-consecutive point configuration which demonstrates the use of a relay site to work-around a line- of-sight obstruction.

  20. F Ring Mini-Jets

    NASA Astrophysics Data System (ADS)

    Attree, N.; Murray, C.; Cooper, N. J.; Williams, G.

    2012-12-01

    Mini-jets are small, (~50 km) linear features observed in Cassini images to be emanating from Saturn's F ring; they are believed to be produced by collisions with a local population of moonlets. An analysis of one such feature, observed over the course of a ~7.5 h sequence as its length changed from ~75 km to ~250 km while it simultaneously appeared to collapse back into the core, supports the collisional theory of their origin [1]. Orbit determination suggests that this mini-jet consisted of ring material displaced by a ~1 m/s collision with a nearby object, resulting in paths relative to the core that are due to a combination of keplerian shear and epicyclic motion. The colliding object itself is likely to be too small to resolve in these images but represents just one member of a population of F ring moonlets. Such a population has been investigated by UVIS occultations [2], and other methods, but generally remains unresolved in Cassini images. Collisional features such as this mini-jet therefore provide an additional tracer for the region's moonlet population. In this talk we will present the results of recent work in measuring and describing a subset of ~350 catalogued mini-jets, applying knowledge gained from the original mini-jet feature. Their distribution in space and time, proximity to Prometheus and evolution are all examined in an effort to place constraints on the properties of the underlying population of colliding objects. References [1] N. O. Attree, C. D. Murray, N. J. Cooper, and G. A. Williams. Detection of low velocity collisions in Saturn's F ring. Ap. J. Lett. (In press). [1] B. K. Meinke, L. W. Esposito, N. Albers, and M. Sremevi. Classification of F ring features observed in cassini UVIS occultations. Icarus, 218(1):545 - 554, 2012.

  1. Recommendation for the Feasibility of more Compact LC Damping Rings

    SciTech Connect

    Pivi, M.T.F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Shibata, K.; Ohmi, K.; Dugan, G.; Palmer, M.; Crittenden, J.A.; Harkay, K.; Boon, L.; Furman, M.A.; Venturini, M.; Celata, C.; Malyshev, O.B.; Papaphilippou, I.; /CERN

    2010-06-15

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of the shorter damping ring with respect to the electron cloud build-up and related beam instabilities. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 [1] and would allow considerable reduction of the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigation techniques and the integration of the CesrTA results into the Damping Ring design.

  2. Recommendation for the Feasibility of more Compact LC Damping Rings

    SciTech Connect

    Pivi, M. T. F.; Wang, L.; Demma, T.; Guiducci, S.; Suetsugu, Y.; Fukuma, H.; Shibata, K.; Dugan, K.,G.; Palmer, M.; Crittenden, J.; Harkay, K.; Boon, L.; Furman, M. A.; Venturini, M.; Celata, C.; Malyshev, O.; Papaphilippou, I.

    2010-05-23

    As part of the international Linear Collider (ILC) collaboration, we have compared the electron cloud (EC) effect for different Damping Ring (DR) designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. The studies for a 3.2 km ring were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design SB2009 [1] and would allow to considerably reduce the number of components, wiggler magnets and costs. We discuss the impact of the proposed operation of the ILC at high repetition rate 10 Hz and address the necessary modifications for the DRs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.

  3. Recording PEP2 Ring Beam Losses at SLAC

    SciTech Connect

    Zelazny, M.; Gromme, T.; Himel, T.; Hendrickson, L.; Krauter, K.; /SLAC

    2005-09-30

    The PEP2 (e+)(e-) storage rings contain many complex interrelated systems. When the beam aborts, examining a record of the orbit from the time just before the abort can help identify the root cause. At the Stanford Linear Accelerator Center (SLAC) a system has been developed to continuously record beam orbits from Beam Position Monitors (BPMS) into a circular buffer. When the beam is aborted the buffers are frozen and their contents are stored for later analysis. BPM orbits are saved on a turn by turn basis for 2800 turns in both the high energy ring (HER) and the low energy ring (LER). Each BPM Processor (BPMP) can either monitor the HER or the LER, but not both as the readout of the two rings is multiplexed into a single readout channel. Tools exist as part of the SLAC Control Program (SCP) to collect, display, and save the data. A physicist or operator can choose a few BPMS in which to view all 2800 turns to identify the turn in which the beam went awry; then ask for that specific orbit from all of the BPMS in the storage ring to determine the root cause of the abort.

  4. Saturn's Magnetosphere, Rings, and Inner Satellites.

    PubMed

    VAN Allen, J A; Thomsen, M F; Randall, B A; Rairden, R L; Grosskreutz, C L

    1980-01-25

    Our 31 August to 5 September 1979 observations together with those of the other Pioneer 11 investigators provide the first credible discovery of the magnetosphere of Saturn and many detailed characteristics thereof. In physical dimensions and energetic charged particle population, Saturn's magnetosphere is intermediate between those of Earth and Jupiter. In terms of planetary radii, the scale of Saturn's magnetosphere more nearly resembles that of Earth and there is much less inflation by entrapped plasma than in the case at Jupiter. The orbit of Titan lies in the outer fringes of the magnetosphere. Particle angular distributions on the inbound leg of the trajectory (sunward side) have a complex pattern but are everywhere consistent with a dipolar magnetic field approximately perpendicular to the planet's equator. On the outbound leg (dawnside) there are marked departures from this situation outside of 7 Saturn radii (Rs), suggesting an equatorial current sheet having both longitudinal and radial components. The particulate rings and inner satellites have a profound effect on the distribution of energetic particles. We find (i) clear absorption signatures of Dione and Mimas; (ii) a broad absorption region encompassing the orbital radii of Tethys and Enceladus but probably attributable, at least in part, to plasma physical effects; (iii) no evidence for Janus (1966 S 1) (S 10) at or near 2.66 Rs; (iv) a satellite of diameter greater, similar 170 kilometers at 2.534 R(s) (1979 S 2), probably the same object as that detected optically by Pioneer 11 (1979 S 1) and previously by groundbased telescopes (1966 S 2) (S 11); (v) a satellite of comparable diameter at 2.343 Rs (1979 S 5); (vi) confirmation of the F ring between 2.336 and 2.371 Rs; (vii) confirmation of the Pioneer division between 2.292 and 2.336 Rs; (viii) a suspected satellite at 2.82 Rs (1979 S 3); (ix) no clear evidence for the E ring though its influence may be obscured by stronger effects; and (x) the

  5. Wear reduction systems liquid piston ring

    SciTech Connect

    Raymond, R.J.; Chen, T.N.; DiNanno, L.

    1990-09-01

    The overall objective of the program was to demonstrate the technical feasibility of achieving an acceptable wear rate for the cylinder liner, piston, and piston rings in a coal/water-slurry-fueled engine that utilized the concept of a liquid piston ring above the conventional piston rings and to identify technical barriers and required research and development. The study included analytical modeling of the system, a bench study of the fluid motion in the liquid piston ring, and a single-cylinder test rig for wear comparison. A system analysis made on the different variations of the liquid supply system showed the desirability of the once-through version from the standpoint of system simplicity. The dynamics of the liquid ring were modeled to determine the important design parameters that influence the pressure fluctuation in the liquid ring during a complete engine cycle and the integrity of the liquid ring. This analysis indicated the importance of controlling heat transfer to the liquid ring through piston and liner to avoid boiling the liquid. A conceptual piston design for minimizing heat transfer is presented in this report. Results showed that the liquid piston ring effectively reduced the solid particles on the wall by scrubbing, especially in the case where a surfactant was added to the water. The wear rates were reduced by a factor of 2 with the liquid ring. However, leakage of the contaminated liquid ring material past the top ring limited the effectiveness of the liquid ring concept. 8 refs., 33 figs., 1 tab.

  6. Local Area Networks: Part II.

    ERIC Educational Resources Information Center

    Dessy, Raymond E., Ed.

    1982-01-01

    Discusses five approaches used by industry/colleges to provide local area network (LAN) capabilities in the analytical laboratory: (1) mixed baseband bus network coupled to a star net; (2) broadband bus network; (3) ring network; (4) star network coupled to broadband net; and (5) simple multiprocessor center. Part I (September issue) focused on…

  7. The Canarias Einstein ring: a newly discovered optical Einstein ring

    NASA Astrophysics Data System (ADS)

    Bettinelli, M.; Simioni, M.; Aparicio, A.; Hidalgo, S. L.; Cassisi, S.; Walker, A. R.; Piotto, G.; Valdes, F.

    2016-09-01

    We report the discovery of an optical Einstein ring in the Sculptor constellation, IAC J010127-334319, in the vicinity of the Sculptor dwarf spheroidal galaxy. It is an almost complete ring (˜300°) with a diameter of ˜4.5 arcsec. The discovery was made serendipitously from inspecting Dark Energy Camera (DECam) archive imaging data. Confirmation of the object nature has been obtained by deriving spectroscopic redshifts for both components, lens and source, from observations at the 10.4 m Gran Telescopio CANARIAS (GTC) with the spectrograph OSIRIS. The lens, a massive early-type galaxy, has a redshift of z = 0.581, while the source is a starburst galaxy with redshift of z = 1.165. The total enclosed mass that produces the lensing effect has been estimated to be Mtot = (1.86 ± 0.23) × 1012 M⊙.

  8. Microwave observations provide clues to the origin of Saturn's main rings

    NASA Astrophysics Data System (ADS)

    Zhang, Zhimeng

    Division particles are more likely to contain ≥ 90% porosity due to its high opacity. We find that the overall pollution exposure time for the A and B rings and the Cassini Division ranges from 40-150 Myr, which is in line with the 15-90 Myr in the C ring. Our results support the idea that Saturn's rings may be ≤ 150 Myr old suggesting an origin scenario in which the rings are derived from the relatively recent breakup of an icy moon. The multi-wavelength VLA observations confirm the high porosity in the C ring particles and the presence of a "hot band" in the middle C ring. In the intramixure model, our multi-wavelength study suggests a corresponding decrease in the imaginary part of the silicates dielectric constant at higher frequencies. However, we do not see evidence for such decrease in the B ring particles. The results support the idea that the silicates in middle C ring has different origin source from meteoroid flux or that the middle C ring particles are more likely to be described by the core-mantle model which naturally matches observations at all wavelengths. Finally, the silicates fraction in the B ring is consistent with that derived from Cassini observations, less than 1%. We confirm that the B ring particles are likely to be over 80% porous, which at the same time explains the high opacity in the B ring measured by density waves.

  9. Contact stresses calculated for miniature slip rings

    NASA Technical Reports Server (NTRS)

    Albright, F. G.; Domerest, K. E.; Horton, J. C.

    1965-01-01

    Using mathematical formulations to plot the graphs of the contact preload versus the Hertzian load, calculations of unit loading of the preloaded brushes on slip rings can be made. This optimizes the design of contact brushes and miniature slip rings.

  10. How to Remove a Stuck Ring Safely

    MedlinePlus

    ... Gardening Safety Turkey Carving Removing a Ring Español Artritis de la base del pulgar Dedo en gatillo ... Gardening Safety Turkey Carving Removing a Ring Español Artritis de la base del pulgar Dedo en gatillo ...

  11. Strange Things Afoot in the B Ring

    NASA Image and Video Library

    2010-11-01

    The outer edge of Saturn B ring exhibits an unexpected feature in this image captured by NASA Cassini spacecraft. The image was obtained when the sun was over the planet equator and lit the rings exactly exactly edge on.

  12. Cassini's First Picture of F Ring

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This is one of the first images taken of Saturn's F ring by the Cassini spacecraft after it successfully entered Saturn's orbit. It was taken by the spacecraft's narrow angle camera and shows the sunlit side of the rings.

  13. Planetary science: Shepherds of Saturn's ring

    NASA Astrophysics Data System (ADS)

    Crida, Aurélien

    2015-09-01

    Saturn's F ring is chaperoned on both sides by the tiny moons Prometheus and Pandora. Numerical simulations show that this celestial ballet can result from the collision of two aggregates that evolved out of Saturn's main rings.

  14. Kinematics and dynamics of the Uranian rings

    NASA Technical Reports Server (NTRS)

    French, Richard G.

    1987-01-01

    The self-gravity model of apse alignment was tested by comparing its predictions about structure within the epsilon ring with an extensive set of observed occultation profiles covering a wide range of ring longitudes. The self-gravity model as presently constructed is inconsistent with the observations. The Lindblad resonance survey and Shepherd satellite ring perturbation are discussed. The kinematic model of the Uranian ring orbit was enhanced to accommodate Voyager observations as well as ground-based occultation observations.

  15. Optical fiber having wave-guiding rings

    DOEpatents

    Messerly, Michael J [Danville, CA; Dawson, Jay W [Livermore, CA; Beach, Raymond J [Livermore, CA; Barty, Christopher P. J. [Hayward, CA

    2011-03-15

    A waveguide includes a cladding region that has a refractive index that is substantially uniform and surrounds a wave-guiding region that has an average index that is close to the index of the cladding. The wave-guiding region also contains a thin ring or series of rings that have an index or indices that differ significantly from the index of the cladding. The ring or rings enable the structure to guide light.

  16. Analysis of Alternative Ring Resonator Designs

    DTIC Science & Technology

    2014-08-01

    the ring strip of the antenna as in the case of the original design. Both the alternative dielectric laminate and the increased thickness laminate...adjustments to the geometry parameters. 2. Ring Resonator Antenna Design The ring resonator is a two port antenna consisting of a ring strip and two...differing thicknesses for resonator antennas of the same design suggests that the RF fields penetrate slightly more or that the resonator can “see” a

  17. Shepherding model for Neptune's arc ring

    NASA Technical Reports Server (NTRS)

    Lissauer, J. J.

    1985-01-01

    A model to explain the confinement of the recently discovered incomplete arc ring around Neptune is developed. The ring may be azimuthally confined near a triangular (Trojan) point of an undiscovered satellite of Neptune. Radial diffusion of the ring particles can be prevented by shepherding torques of another moon. Two satellites with diameters of 100-200 km would be sufficient to confine the ring; such moons would be too small to have been photographed from earth.

  18. Random Implantation of Asymmetric Intracorneal Rings

    PubMed Central

    Peris-Martínez, Cristina; Gregori Gisbert, Irene

    2014-01-01

    Intracorneal ring employment for treating ectasia is widespread. Although the mechanism of action of intracorneal rings in the regularization of the corneal surface after its implantation is well known in most cases, there are still many doubts. We present a case of implanted intracorneal rings, where, despite the peculiar position of the rings, the patient gains lines of visual acuity and keratoconus remains stable. PMID:24711941

  19. An Instability in Narrow Planetary Rings

    NASA Astrophysics Data System (ADS)

    Weiss, J. W.; Stewart, G. R.

    2003-08-01

    We will present our work investigating the behavior of narrow planetary rings with low dispersion velocities. Such narrow a ring will be initially unstable to self-gravitational collapse. After the collapse, the ring is collisionally very dense. At this stage, it is subject to a new instability. Waves appear on the inner and outer edges of the ring within half of an orbital period. The ring then breaks apart radially, taking approximately a quarter of an orbital period of do so. As clumps of ring particles expand radially away from the dense ring, Kepler shear causes these clumps to stretch out azimuthally, and eventually collapse into a new set of dense rings. Small-scale repetitions of the original instability in these new rings eventually leads to a stabilized broad ring with higher dispersion velocities than the initial ring. Preliminary results indicate that this instability may be operating on small scales in broad rings in the wake-like features seen by Salo and others. Some intriguing properties have been observed during this instability. The most significant is a coherence in the epicyclic phases of the particles. Both self-gravity and collisions in the ring operated to create and enforce this coherence. The coherence might also be responsible for the instability to radial expansion. We also observe that guiding centers of the particles do not migrate to the center of the ring during the collapse phase of the ring. In fact, guiding centers move radially away from the core of the ring during this phase, consistent with global conservation of angular momentum. We will show the results of our simulations to date, including movies of the evolution of various parameters. (Audiences members wanting popcorn are advised to bring their own.) This work is supported by a NASA Graduate Student Research Program grant and by the Cassini mission.

  20. EDGE-ON VIEW OF SATURN'S RINGS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is a NASA Hubble Space Telescope snapshot of Saturn with its rings barely visible. Normally, astronomers see Saturn with its rings tilted. Earth was almost in the plane of Saturn's rings, thus the rings appear edge-on. In this view, Saturn's largest moon, Titan, is casting a shadow on Saturn. Titan's atmosphere is a dark brown haze. The other moons appear white because of their bright, icy surfaces. Four moons - from left to right, Mimas, Tethys, Janus, and Enceladus - are clustered around the edge of Saturn's rings on the right. Two other moons appear in front of the ring plane. Prometheus is on the right edge; Pandora, on the left. The rings also are casting a shadow on Saturn because the Sun was above the ring plane. [bottom] - This photograph shows Saturn with its rings slightly tilted. The moon called Dione, on the lower right, is casting a long, thin shadow across the whole ring system due to the setting Sun on the ring plane. The moon on the upper left of Saturn is Tethys. Astronomers also are studying the unusual appearance of Saturn's rings. The bottom image displays a faint, narrow ring, the F-ring just outside the main ring, which normally is invisible from Earth. Close to the edge of Saturn's disk, the front section of rings seem brighter and more yellow than the back due to the additional lumination by yellowish Saturn. The color images were assembled from separate exposures taken August 6 (top) and November 17 (bottom), 1995 with the Wide Field Planetary Camera-2. CREDIT: Erich Karkoschka (University of Arizona Lunar and Planetary Lab) and NASA