| 1. |
- Blideanu, V., et al.
(författare)
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Nucleon-induced reactions at intermediate energies : New data at 96 MeV and theoretical status
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 70:1, s. 014607-
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Tidskriftsartikel (refereegranskat)abstract
- Double-differential cross sections for light charged particle production (up to A=4) were measured in 96 MeV neutron-induced reactions, at the TSL Laboratory Cyclotron in Uppsala (Sweden). Measurements for three targets, Fe, Pb, and U, were performed using two independent devices, SCANDAL and MEDLEY. The data were recorded with low-energy thresholds and for a wide angular range (20°–160°). The normalization procedure used to extract the cross sections is based on the np elastic scattering reaction that we measured and for which we present experimental results. A good control of the systematic uncertainties affecting the results is achieved. Calculations using the exciton model are reported. Two different theoretical approaches proposed to improve its predictive power regarding the complex particle emission are tested. The capabilities of each approach is illustrated by comparison with the 96 MeV data that we measured, and with other experimental results available in the literature.
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| 2. |
- Johansson, A., et al.
(författare)
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The solution thermolysis approach to molybdenum(V) alkoxides : synthesis, solid state and solution structures of the bimetallic alkoxides of molybdenum(V) and niobium(V), tantalum(V) and tungsten(VI)
- 2000
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Ingår i: Journal of the Chemical Society-Dalton Transactions. - : Royal Society of Chemistry (RSC). - 0300-9246 .- 1470-479X .- 1364-5447. ; :3, s. 387-394
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Tidskriftsartikel (refereegranskat)abstract
- No complex formation can be observed between molybdenum(VI) oxoalkoxides and the alkoxides of niobium(V) or tantalum(V) at room temperature. The bimetallic derivatives of molybdenum(V), Mo4M2O8((OPr)-Pr-i)(14), where M=Nb 1 and Ta 2, were instead isolated on cooling from the solutions of the isopropoxides in toluene subjected to a short-time reflux. The X-ray single crystal study showed both 1 and 2 to be built of ((PrO)-Pr-i)(3)M(mu-(OPr)-Pr-i)(3)MoO(mu-O)(2)MoO(mu-(OPr)-Pr-i)(2)MoO(mu-O)(2)MoO(mu-(OPr)-Pr-i)(3)M((OPr)-Pr-i)(3) non-linear chain molecules with 2 Mo-Mo bonds (2.5836(8) Angstrom) and short but non-bonding Mo-M distances (3.1791(8) Angstrom for 1 and 3.1746(8) Angstrom for 2). According to NMR and EXAFS data this structure becomes very fluxional or might even be partially broken into homometallic components in hydrocarbon solutions. The oxidation of 2 with traces of oxygen leads to the formation of Mo3Ta2O8((OPr)-Pr-i)(10) 3. Compound 3 can be isolated in a pure form from the reaction of MoO((OPr)-Pr-i)(4) with Ta((OPr)-Pr-i)(4)(OMe) 6: the presence of methoxide ligands leads to the formation of additional oxoligands via non-reductive thermolysis leading to the formation of a (CH3)(2)C(OMe)(2) ketal as organic byproduct. The molecules of 3 are 5-member rings with a MoO(mu-O)(2)MoO fragment in the basis (Mo-Mo 2.5730(13) Angstrom), coupled to two (mu-(OPr)-Pr-i)(2)Ta((OPr)-Pr-i)(3) fragments that are joined together by an oxomolybdate ligand (mu-O)(2)MoO2. According to NMR-spectroscopic data the aggregate is preserved and rigid in solution. Mo4Ta4O16((OPr)-Pr-i)(12) 4 was found to be one of the products of complete oxidation of 2 (and 3) on prolonged contact with dry oxygen. The thermal treatment of the solutions of MoO((OPr)-Pr-i)(4) and WO((OPr)-Pr-i)(4) in toluene yields (Mo4O8)-O-V(Mo,W)O-VI(2)2((OPr)-Pr-i)(12) 5 with a molecular structure very close to its homometallic analog Mo6O10((OPr)-Pr-i)(12). The complete X-ray single crystal study was carried out for the sample of 5 with (Mo4O8)-O-V(Mo0.45W0.55)O-VI(2)2((OPr)-Pr-i)(12) composition.
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| 3. |
- Hertz, Hans M., et al.
(författare)
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Liquid-jet laser-plasma X-ray sources for microscopy and lithography
- 2001
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Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 11:PR2, s. 389-396
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Tidskriftsartikel (refereegranskat)abstract
- We review the development of compact laser-plasma soft x-ray sources based on microscopic liquid-drop or liquid-jet targets. It is shown that such sources provide practically debris-free, high-flux operation at water-window and EUV wavelengths. This regenerative and solid-density target system holds promise for the generation of high-average power using high-repetition-rate lasers. Application of the source to compact x-ray microscopy, multi layer-op tics characterization and EUV lithography is briefly discussed.
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| 4. |
- Johansson, E. M., et al.
(författare)
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Development of hexaaluminate catalysts for combustion of gasified biomass in gas turbines
- 2002
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 124:2, s. 235-238
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Tidskriftsartikel (refereegranskat)abstract
- There is an increasing interest in Catalytic combustors fuelled by low-heating value (LHV) gases, with a LHV of 5-7 MJ/Nm(3). This is because catalytic combustion could be advantageous compared to flame combustion with respect to stable combustion of LHV-gases and low conversions of fuel-N (mainly NH3) to NOX. In the present project, funded by the EU Joule Program, catalytic combustion of gasified wood for gas turbine applications is studied. A synthetic gas mixture of H-2, CO, CO2, H2O, CH4, N-2, and NH3, that resembles the output from a fluidized bed gasifier using biomass as raw material, is used. The gas mixture is mixed with air at atmospheric pressure and combusted over wash-coated cordierite monoliths in a bench-scale laboratory quartz-reactor. The objectives of the work described here are twofold. To begin with, improvement of the thermal stability of hexaaluminate washcoats by substitutions of rare earth or transition metal compounds is being studied. Secondly, catalytic combustion of gasified biomass over these washcoats has been studied in a bench-scale unit. In. this on-going project, obtained result show that it is possible to improve the surface area of hexaaluminate compounds up to 17 m(2)/g after careful synthesis and calcination up to 1400degreesC for four hours. The selectivity of NH3-conversion to N-2 is at present at 60 percent, but varies strongly with temperature. Fuel components such as H-2, CO, C2H4, and NH3 ignite at temperatures close to compressor outlet temperatures. This means that a pilot-flame may not be needed for ignition of the fuel. A comparison between a Pd-impregnated lanthanum hexaaluminate and a Mn-substituted lanthanum hexaaluminate showed that the ignition temperature and the NOX-formation varied strongly over the two different catalysts.
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| 5. |
- Johansson, Göran A., et al.
(författare)
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Exploring the use of soft X-ray microscopy for imaging subcellular structures of the inner ear
- 2004
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Ingår i: Journal of Microscopy. - : Wiley. - 0022-2720 .- 1365-2818. ; 215, s. 203-212
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Tidskriftsartikel (refereegranskat)abstract
- The soft X-ray microscope at the Lawrence Berkeley National Laboratory was developed for visualization of biological tissue. Soft X-ray microscopy provides high-resolution visualization of hydrated, non-embedded and non-sectioned cells and is thus potentially an alternative to transmission electron microscopy. Here we show for the first time soft X-ray micrographs of structures isolated from the guinea-pig inner ear. Sensory outer hair cells and supporting pillar cells are readily visualized. In the hair cells, individual stereocilia can easily be identified within the apical hair bundle. The underlying cuticular plate is, however, too densely composed or too thick to be clearly visualized, and thus appears very dark. The cytoplasmic structures protruding from the cuticular plates as well as the fibrillar material surrounding and projecting from the cell nuclei can be seen. In the pillar cells the images reveal individual microtubule bundles. Soft X-ray images of the acellular tectorial membrane and thin two-layered Reissner's membrane display a level of resolution comparable to low-power electron microscopy.
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| 6. |
- Eriksson, Fredrik, et al.
(författare)
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14.5% near-normal incidence reflectance of Cr/Sc x-ray multilayer mirrors for the water window
- 2003
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Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 28:24, s. 2494-2496
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Tidskriftsartikel (refereegranskat)abstract
- Cr/Sc multilayer mirrors, synthesized by ion-assisted magnetron sputter deposition, are proved to have a high near-normal reflectivity of R = 14.5% at a grazing angle of 87.5degrees measured at the wavelength A = 3.11 nm, which is an improvement of more than 31% compared with previously published results. Elastic recoil detection analyses show that the mirrors contained as much as 15 at. % of N and traces of C and O. Soft x-ray reflectivity simulations reveal interface widths of sigma = 0.34 nm and an exceptionally small layer thickness drift of similar to1.6 X 10(-5) nm/multilayer period throughout the stack. Simulations show that a reflectivity of R = 25.6% is attainable if impurities and layer thickness drift can be eliminated. The abrupt interfaces are achieved with ion assistance with a low ion energy of 24 eV and high ion-to-metal flux ratios of 7.1 and 23.1 during Cr and Se sputter deposition, respectively. In addition, a near-normal incidence reflectivity of 5.5% for the C VI emission line (lambda = 3.374 nm) from a laser plasma source was verified.
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| 7. |
- Johansson, G. A., et al.
(författare)
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Compact soft x-ray reflectometer based on a line-emitting laser-plasma source
- 2001
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 72:1, s. 58-62
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Tidskriftsartikel (refereegranskat)abstract
- We describe a compact soft x-ray reflectometer for in-house characterization of water-window multilayer optics. The instrument is based on a line-emitting, liquid-jet, laser-plasma source in combination with angular scanning of the studied multilayer optics. With a proper choice of target liquid and thin-film filters, one or a few lines of well-defined wavelength dominate the spectrum and multilayer periods are measured with an accuracy of 0.003 nm using a multi-line calibration procedure. Absolute reflectivity may also be estimated with the instrument. The typical measurement time is currently 10 min. Although the principles of the reflectometer may be used in the entire soft x-ray and extreme ultraviolet range, the current instrument is primarily directed towards normal-incidence multilayer optics for water-window x-ray microscopy, and is thus demonstrated on W/B4C multilayers for this wavelength range.
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| 8. |
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| 9. |
- Sharma, P., et al.
(författare)
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Ferromagnetism above room temperature in bulk and transparent thin films of Mn-doped ZnO
- 2003
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Ingår i: Nature Materials. - : Springer Science and Business Media LLC. - 1476-1122 .- 1476-4660. ; 2:10, s. 673-677
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Tidskriftsartikel (refereegranskat)abstract
- The search for ferromagnetism above room temperature in dilute magnetic semiconductors has been intense in recent years. We report the first observations of ferromagnetism above room temperature for dilute (<4 at.%) Mn-doped ZnO. The Mn is found to carry an average magnetic moment of 0.16 μ(B) per ion. Our ab initio calculations find a valance state of Mn2+ and that the magnetic moments are ordered ferromagnetically, consistent with the experimental findings. We have obtained room-temperature ferromagnetic ordering in bulk pellets, in transparent films 2-3 μm thick, and in the powder form of the same material. The unique feature of our sample preparation was the low-temperature processing. When standard high-temperature (T>700degreesC) methods were used, samples were found to exhibit clustering and were not ferromagnetic at room temperature. This capability to fabricate ferromagnetic Mn-doped ZnO semiconductors promises new spintronic devices as well as magneto-optic components.
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| 10. |
- Bexell, U., et al.
(författare)
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A ToF-SIMS study of linseed oil bonded to mercapto silane treated aluminium
- 2004
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 231-2, s. 362-365
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Tidskriftsartikel (refereegranskat)abstract
- ToF-SIMS has been used to analyse an aluminium surface treated with a vegetable oil using a mercapto silane as a coupling agent between the aluminium substrate and the vegetable oil. The coupling between the vegetable oil and the mercapto silane was obtained through a photoinduced thiol-ene reaction using UV-radiation. The ToF-SIMS results show that the desired thiolene reaction has taken place between the unsaturated parts of the vegetable oil and the thiol groups of the mercapto silane via the thiol-ene reaction forming a surface film.
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