| 1. |
- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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| 2. |
- Torkar, K., Riedler, W., Escoubet, C.P., Fehringer, M., Schmidt, R., Grard, R.J., Arends, H., Rudenauer, F., Steiger, W., Narheim, B.T., Svenes, K., Torbert, R., Andre, M., Fazakerley, A., Goldstein, R., Olsen, R.C., Pedersen, A., Whipple, E. and Zhao, H.
(författare)
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Active spacecraft potential control for Cluster - implementation and first results
- 2001
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Ingår i: Annales Geophysicae. ; 9:10-12, s. 1289-1302
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Tidskriftsartikel (refereegranskat)abstract
- Electrostatic charging of a spacecraft modifies the distribution of electrons and ions before the particles enter the sensors mounted on the spacecraft body. The floating potential of magnetospheric satellites in sunlight very often reaches several tens o
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| 3. |
- Wang, C. K., et al.
(författare)
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Solvent effects on the electronic structure of a newly synthesized two-photon polymerization initiator
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 119:2, s. 1208-1213
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent hybrid density functional theory in combination with polarized continuum model has been applied to study the solvent effects on the geometrical and electronic structures, as well as one- and two-photon absorption processes, of a newly synthesized asymmetrical charge-transfer (CT) two-photon absorption (TPA) organic molecule. The TPA cross section calculated from a generalized two-state model and solvatochromic shift of the CT state are found to be solvent dependent, for which a nonmonotonic behavior with respect to the polarity of the solvents has been observed. The calculated properties are in good agreement with the experimental data available. The character of the CT state is visualized by plotting its charge density difference from ground state, in which an excess of electron density on the donor side of the molecule is found. This implies that the excited molecule is ready to donate its electron to the surroundings. The energetic aspect of the electron donation is discussed by examining the solvent dependence of the molecular ground state oxidation potential. The importance of the electron correlation for describing the two-photon absorption is also demonstrated.
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| 4. |
- Wang, X., et al.
(författare)
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Involvement of the MKK6-p38? cascade in ?-radiation-induced cell cycle arrest
- 2000
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Ingår i: Molecular and Cellular Biology. - 0270-7306 .- 1098-5549. ; 20:13, s. 4543-4552
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Tidskriftsartikel (refereegranskat)abstract
- The p38 group of kinases belongs to the mitogen-activated protein (MAP) kinase superfamily with structural and functional characteristics distinguishable from those of the ERK, JNK (SAPK), and BMK (ERK5) kinases. Although there is a high degree of similarity among members of the p38 group in terms of structure and activation, each member appears to have a unique function. Here we show that activation of p38-? (also known as ERK6 or SAPK3), but not the other p38 isoforms, is required for ?-irradiation- induced G2 arrest. Activation of the MKK6-p38? cascade is sufficient to induce G2 arrest in cells, and expression of dominant negative alleles of MKK6 or p38? allows cells to escape the DNA damage-induce G2 delay. Activation of p38? is dependent on ATM and leads to activation of Cds1 (also known as Chk2). These data suggest a model in which activation of ATM by ? irradiation leads to the activation of MKK6, p38?, and Cds1 and that activation of both MKK6 and p38? is essential for the proper regulation of the G2 checkpoint in mammalian cells.
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| 5. |
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| 6. |
- Wu, Felix, et al.
(författare)
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draft-wu-pana-dpac-framework-00
- 2003
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- This informational draft describes the DPAC (Data Packet Access Control) framework, potentially under PANA, to efficiently control "data packets" to access the network. Instead of using potentially more expensive crypto-based mechanisms such as IPSec (layer 3) or IEEE 802.11i (layer 2), DPAC introduces the possibility of using and negotiating a range of light-weight per-data-packet source authentication methods to control the data packets from PANA Clients (PaC). In DPAC, each data packet sent from PaCs to Enhanced Point (EP) can be classified, with high probability, as either valid or invalid. Furthermore, under this framework, it is possible for EP and PAA to account reliably on the network usage of each PaC.
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| 7. |
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| 8. |
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| 9. |
- Buscaglia, M. T., et al.
(författare)
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Ferroelectric properties of dense nanocrystalline BaTiO3 ceramics
- 2004
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Ingår i: Nanotechnology. - : IOP Publishing. - 0957-4484 .- 1361-6528. ; 15:9, s. 1113-1117
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Tidskriftsartikel (refereegranskat)abstract
- Dense BaTiO3 ceramics with 50 nm average grain size obtained by spark plasma sintering were investigated. The dielectric data show a broad ferro-para phase transition with a maximum permittivity of approximate to1100 at 390 K and 1 kHz. The local ferroelectric switching behaviour was investigated by piezoresponse force microscopy. Typical piezoelectric hysteresis loops were recorded at different positions of the sample. The present results provide experimental evidence for polarization switching at the local scale, indicating that the critical grain size for the disappearance of ferroelectric behaviour in dense, bulk BaTiO3 nanocrystalline ceramics is below 50 nm.
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| 10. |
- Bäckhed, Fredrik, 1973, et al.
(författare)
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Gastric mucosal recognition of Helicobacter pylori is independent of Toll-like receptor 4
- 2003
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Ingår i: J Infect Dis. - 0022-1899. ; 187:5, s. 829-36
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Tidskriftsartikel (refereegranskat)abstract
- Little is known about the interactions between Helicobacter pylori, which specializes in colonizing the mucin layer that covers the gastric mucosa, and primary gastric epithelial cells. The expression pattern of Toll-like receptors (TLRs) in primary gastric epithelial cells and cell lines was compared. Primary cells did not express TLR4, whereas all cell lines expressed a nonsignaling form of TLR4. Because other cells within the mucosa expressed TLR4, it was next investigated whether H. pylori can be recognized by TLR4--they cannot. Moreover, H. pylori infection of primary cells induced a regulated production of interleukin (IL)-6, IL-8, and tumor necrosis factor-alpha, whereas infection of cell lines only resulted in IL-8 production. The cytokine production in all cell types was strictly cag dependent. These findings indicate that, although the epithelium is important in directing the immune response against H. pylori infections, the response is independent of TLR4.
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