| 1. |
- Abazov, V. M., et al.
(författare)
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The upgraded DO detector
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
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Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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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. |
- Zheng, L. R., et al.
(författare)
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Network Structured SnO2/ZnO Heterojunction Nanocatalyst with High Photocatalytic Activity
- 2009
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Ingår i: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 48:5, s. 1819-1825
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Tidskriftsartikel (refereegranskat)abstract
- A network-structured SnO2/ZnO heterojunction nanocatalyst with high photocatalytic activity was successfully synthesized through a simple two-step solvothermal method. The as-synthesized samples are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, N-2 physical adsorption, and UV-vis spectroscopy. The results show that the SnO2/ZnO sample with a molar ratio of Sn/Zn = 1 is a mesoporous composite material composed of SnO2 and ZnO. The photocatalytic activity of SnO2/ZnO heterojunction nanocatalysts for the degradation of methyl orange is much higher than those of solvothermally synthesized SnO2 and ZnO samples, which can be attributed to the SnO2-ZnO heterojunction, the pore structure, and higher Brunauer-Emmeff-Teller (BET) surface area of the sample: (1) The SnO2-ZnO heterojunction improves the separation of photogenerated electron-hole pairs due to the potential energy differences between SnO2 and ZnO, thus enhancing the photocatalytic activity. (2) The SnO2/ZnO sample might possess more surface reaction sites and adsorb and transport more dye molecules due to the higher BET surface area and many pore channels, also leading to higher photocatalytic activity.
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| 4. |
- Zhang, Fengling, et al.
(författare)
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Ordered mesoporous Ag-TiO2-KIT-6 heterostructure: synthesis, characterization and photocatalysis
- 2009
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 19:18, s. 2771-2777
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Tidskriftsartikel (refereegranskat)abstract
- Ordered mesoporous Ag-TiO2-KIT-6 heterostructured nanocrystals were successfully synthesized by a template-based method, where a layer of TiO2 and Ag2O nanoparticles were deposited on cubic (Ia3d) silica (KIT-6) in an orderly manner; at the same time, the formed Ag2O nanoparticles were photolyzed to metallic Ag nanoparticles. Our results show that Ag-TiO2-KIT-6 is an ordered mesoporous composite material, which is composed of Ag-TiO2 heterostructures and the amorphous KIT-6 template. In addition, Ag-TiO2-KIT-6 possesses the highest photocatalytic activity among the as-synthesized photocatalysts, which can be attributed to the Ag-TiO2 heterojunctions and the excellent texture: (1) Ag-TiO2 heterojunctions improve the separation of photogenerated electron-hole pairs due to the potential energy differences between Ag and TiO2 nanocrystals, thus enhancing the photocatalytic activity; (2) the Ag-TiO2-KIT-6 sample possesses a high BET surface area and a large number of ordered pore channels, which facilitate adsorption and transportation of dye molecules, also leading to higher photocatalytic activity. It was also found that the Ag-TiO2 heterostructure plays a more important role in enhancing the photocatalytic activity than high BET surface area.
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| 5. |
- Zheng, Y. H., et al.
(författare)
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Photocatalytic activity of Ag/ZnO heterostructure nanocatalyst: Correlation between structure and property
- 2008
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Ingår i: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 112:29, s. 10773-10777
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Tidskriftsartikel (refereegranskat)abstract
- Ag/ZnO heterostructure nanocatalysts with Ag content of 1 wt % are successfully prepared through three different simple methods, where chemical reduction and photolysis reaction are adopted to fabricate the heterostructure. The dispersity of Ag clusters and/or nanoparticles in Ag/ZnO nanocatalyst is investigated by EDX mapping and XPS techniques. The experimental results show that deposition-precipitation is an efficient method to synthesize Ag/ZnO nanocatalyst with highly dispersed Ag clusters and/or nanoparticles; the photocatalytic activity of Ag/ZnO photocatalysts mainly depends on the dispersity of metallic Ag in Ag/ZnO nanocatalyst; the higher the dispersity of metallic Ag in Ag/ZnO nanocatalyst is, the higher the photocatalytic activity of Ag/ZnO photocatalyst should be. In addition, it is also found that the dispersity of Ag/ZnO photocatalyst in the dye solution is another key factor for liquid-phase photocatalysis due to the UV-light utilizing efficiency. The higher the UV-light utilizing efficiency is, the higher the photocatalytic activity of Ag/ZnO heterostructure photocatalyst should be.
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| 6. |
- Ohtani, S., et al.
(författare)
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Cluster observations in the inner magnetosphere during the 18 April 2002 sawtooth event : Dipolarization and injection at r=4.6 R-E
- 2007
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202. ; 112:A8
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Tidskriftsartikel (refereegranskat)abstract
- The present study examines a sawtooth injection event that took place around 0800 UT on 18 April 2002 when the Cluster spacecraft were located in the inner magnetosphere in the premidnight sector. In association with this injection, Cluster, at a radial distance of 4.6 RE, observed that the local magnetic field became more dipolar and that both ion and electron fluxes increased without notable energy dispersion. These features were accompanied by intensifications of the equatorward component of a double- oval structure and also by an enhancement of the ring- current oxygen ENA flux. The event was also accompanied by large magnetic field ( a few tens of nT) and electric field ( a few tens of mV/ m) fluctuations with characteristic timescales of a few tens of seconds. These observations strongly suggest that this sawtooth injection extended not only widely in local time but also deeply into the inner magnetosphere. Interestingly, Cluster repeatedly observed dipolarization- like signatures afterward, which, however, were not associated with enhancements of local energetic ion flux or with geosynchronous dipolarization or injection signatures. Instead, these magnetic signatures were accompanied by oscillatory plasma motion in the radial direction with a characteristic timescale of about 10 min, which appears to be related to the westward propagation of a spatially periodic auroral structure. The associated azimuthal electric field component was well correlated with the time derivative of the north- south magnetic field component, suggesting that the observed electric field is inductive. These findings suggest that electromagnetic processes far inside geosynchronous orbit play an important role in energization of energetic ions and auroral dynamics during magnetospheric storms.
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| 7. |
- Wei, S., et al.
(författare)
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Historical trends of organic pollutants in sediment cores from Hong Kong
- 2008
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Ingår i: Marine Pollution Bulletin. - : Elsevier. - 0025-326X .- 1879-3363. ; 57:6-12, s. 758-766
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Tidskriftsartikel (refereegranskat)abstract
- Recent studies have indicated the occurrence of a wide range of trace organic contaminants, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the Hong Kong environment. These contaminants are potentially harmful to ecological systems, particularly in coastal areas. In this study, two sediment cores (4 m) were collected from southern waters of Hong Kong in 2004 to study the historical trends, distribution patterns, and potential sources of trace organic contaminants. DDTs (p,p′-DDT, o,p′-DDT, p,p′-DDD, o,p′-DDD and p,p′-DDE), hexachlorohexanes (HCHs) (α and γ), hexachlorobenzene (HCB), and PCBs were detected in the samples, whereas other target compounds were all below detection limits. Many OCPs have not been produced or used for many years due to toxicological or environmental concerns and PCB use is prohibited in Hong Kong. However, some compounds were still detectable in recent years, and were found to be widely distributed in the environment, likely because of pollutant inputs from the highly industrialized Pearl River Delta region. These results provide important information on current and historical contamination in Hong Kong, and help to reconstruct the pollution history of these trace organic pollutants in Hong Kong coastal waters.
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