| 1. |
- Acciari, V. A., et al.
(författare)
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Radio Imaging of the Very-High-Energy gamma-Ray Emission Region in the Central Engine of a Radio Galaxy
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 325:5939, s. 444-448
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Tidskriftsartikel (refereegranskat)abstract
- The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.
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| 2. |
- Ablikim, M., et al.
(författare)
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Measurements of (XcJ)-> K+K-K+K- decays
- 2006
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Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 642:3, s. 197-202
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Tidskriftsartikel (refereegranskat)abstract
- Using 14M psi(2S) events taken with the BESII detector, chi(cJ) -> 2(K+K-) decays are studied. For the four-kaon final state, the branching fractions are B(chi(c0,1,2) ->.2(K+K-)) = (3.48 +/- 0.23 +/- 0.47) x 10(-3), (0.70 +/- 0.13 +/- 0.10) x 10(-3), and (2.17 +/- 0.20 +/- 0.31) x 10(-3). For the phi K+K- final state, the branching fractions, which are measured for the first time, are B(chi(c0,1,2) -> phi K+K-) = (1.03 +/- 0.22 +/- 0.15) x 10(-3), (0.46 +/- 0.16 +/- 0.06) x 10(-3), and (1.67 +/- 0.26 +/- 0.24) x 10(-4). For the phi phi final state, B(chi(c0,2) -> phi phi) = (0.94 +/- 0.21 +/- 0.13) x 10(-3) and (1.70 +/- 0.30 +/- 0.25) x 10(-3).
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| 3. |
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| 4. |
- Cui, J., et al.
(författare)
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Diurnal variations of Titan's ionosphere
- 2009
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114:6, s. A06310-
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Tidskriftsartikel (refereegranskat)abstract
- We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of similar to 700 cm(-3) below similar to 1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast'' ion-neutral chemistry and the latter through "slow'' electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.
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| 5. |
- Shi, F., et al.
(författare)
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Synthesis and characterization of two novel high valent dinuclear complexes with a triphenolate ligand bearing functional groups
- 2005
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Ingår i: Chinese Chemical Letters. - 1001-8417 .- 1878-5964. ; 16:1, s. 89-92
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Tidskriftsartikel (refereegranskat)abstract
- Two novel high valent complexes [M-2(III, III)L(mu-OAc)(2)](PF6)-P-. (M=Mn, Fe; 9) were prepared, where L was the tri-anion of 2,6-bis{[(2-hydroxy-3-(morpholin-4-yl methyl)-5-tertbutyl benzyl)(pyridyl-2-methyl)amino]methyl}-4-methyl phenol which contained additional phenolic, tert-butyl and morpholin-4-yl methyl groups compared to its parent [Mn-2(II, II)(bpmp) (mu-OAc)(2)](CIO4)-C-. (10). These improvements decreased the difference between the new model and (Mn)(4) cluster (OEC in nature).
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| 6. |
- Steinmuller, S. J., et al.
(författare)
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Effect of substrate roughness on the magnetic properties of thin fcc Co films
- 2007
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:5, s. 054429-
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the influence of substrate roughness on the magnetic properties of thin fcc Co films (7 and 17 nm thick) grown on Cu(001)/Si(001). A significant decrease in cubic anisotropy with increasing film roughness was observed with Brillouin light scattering and magneto-optical Kerr effect magnetometry. In addition, the rougher samples showed a substantial broadening of the spin wave peaks. Both effects were found to be more pronounced for the thinner Co layers. Our observations are discussed in the framework of a theoretical model which takes into account the morphology of the Co films as measured by atomic force microscopy. While roughness effects are usually discussed in the context of Néel's "orange-peel" model, we propose a qualitatively different effect in this work whereby the magnetization follows coherently the substrate morphology ("undulating" state) resulting in the absence of magnetic surface charges. This magnetic configuration gives rise to a reduction in the magnetic anisotropy of epitaxial thin films, which is in good qualitative agreement with the experimental observations.
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| 7. |
- Steinmuller, S. J., et al.
(författare)
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Influence of substrate roughness on the magnetic properties of thin fcc Co films
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:9, s. 09D113-
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Tidskriftsartikel (refereegranskat)abstract
- We present a study of the influence of substrate roughness on the magnetic properties of thin fcc Co films (7 and 17 nm thick) grown on Cu (001) Si (001). A significant decrease in cubic anisotropy with increasing film roughness was observed with Brillouin light scattering. In addition, the rougher samples exhibited a substantial broadening of the spin wave peaks. Both effects were found to be more pronounced for the thinner Co layers. We propose a magnetic configuration with the magnetization following coherently the substrate morphology ("undulating" state) resulting in the absence of magnetic surface charges. This configuration gives rise to a reduction in the magnetic anisotropy of epitaxial thin films, in good qualitative agreement with the experimental observations.
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| 8. |
- Wahlund, Jan Erik, et al.
(författare)
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On the amount of heavy molecular ions in Titan's ionosphere
- 2009
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 57:14-15, s. 1857-1865
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Tidskriftsartikel (refereegranskat)abstract
- We present observational evidence that the ionosphere of Titan below an altitude of 1150 km is a significant source of heavy (> 100 amu) molecular organic species. This study is based on measurements by five instruments (RPWS/LP, RPWS/E, INMS, CAPS/ELS, CAPS/IBS) onboard the Cassini spacecraft during three flybys (T17, T18, T32) of Titan. The ionospheric peaks encountered at altitudes of 950-1300 km had densities in the range 900-3000 cm(-3). Below these peaks the number densities of heavy positively charged ions reached 100-2000 cm(-3) and approached 50-70% of the total ionospheric density with an increasing trend toward lowest measured altitudes. Simultaneously measured negatively charged ion densities were in the range 50-150 cm(-3). These results imply that similar to 10(5)similar to 10(6) heavy positively charged ions/m(3)/s are continuously recombining into heavy neutrals and supply the atmosphere of Titan. The ionosphere may in this way produce 0.1-1 Mt/yr of heavy organic compounds and is therefore a sizable source for aerosol formation. We also predict that Titan's ionosphere is dominated by heavy (> 100 amu) molecular ions below 950 km.
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| 9. |
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