| 1. |
- Niessen, Peter, et al.
(författare)
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Recent results from the amanda experiment
- 2003
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Ingår i: Proceedings of 38th Rencontres de Moriond on Electroweak Interactions and Unified Theories 15-22 Mar 2003. Les Arcs, France.
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Konferensbidrag (refereegranskat)abstract
- AMANDA (Antarctic Muon And Neutrino Detector Array) is a neutrino telescope built under the southern polar icecap and its scope is to explore the possibility to detect high energy cosmic neutrinos. This should generate insight into the powerful celestial objects where acceleration mechanisms can bring up to 10 20 eV. We describe the achievements and results from the AMANDA-B10 prototype and the preliminary results from the current AMANDA-II detector which show dramatic increase in sensitivity.
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| 2. |
- Jahan, D., et al.
(författare)
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Kinetic study of InP : Fe growth by LP-HVPE with ferrocene as Fe source
- 2000
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 147:2, s. 744-746
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Tidskriftsartikel (refereegranskat)abstract
- A kinetic study of InP:Fe growth has been carried out in a low pressure hydride vapor phase epitaxy (LP-HVPE) reactor using Ferrocene as iron source. The influence of the ferrocene partial pressure on the growth behavior has been investigated. A drastic decrease of the growth rate in the presence of ferrocene has been experimentally measured. This effect is explained to be due to cyclopentadiene adsorption. A kinetic model, that takes into account this adsorption, is proposed, which explains the observed experimental results.
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| 3. |
- Messmer, E. R., et al.
(författare)
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Properties of semi-insulating GaAs : Fe grown by hydride vapor phase epitaxy
- 2000
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 147:8, s. 3109-3110
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we analyze GaAs grown by hydride vapor phase epitaxy (HVPE) and doped with four different iron concentrations between 4 X 10(16) and 4.5 X 10(20) cm(-3). From temperature dependent current-voltage measurements we observed the highest resistivity in the lowest doped sample. We also quantified the activation energy. These results together with those of time resolved photoluminescence measurements indicate that in the sample with the lowest Fe concentration, EL2 may be dominant. From the analysis of the time resolved photoluminescence measurements, the intrinsic EL2 concentration and the electron and hole capture cross sections of Fe in GaAs were estimated.
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| 4. |
- Soderstrom, D., et al.
(författare)
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Dopant diffusion and current-voltage studies on epitaxial InP codoped with Ru and Fe
- 2001
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Ingår i: Journal of Electronic Materials. - 0361-5235 .- 1543-186X. ; 30:8, s. 972-976
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Tidskriftsartikel (refereegranskat)abstract
- Semi-insulating Fe and Ru codoped InP epitaxial layers grown by low-pressure hydride vapor phase epitaxy have been investigated. InP:Ru and InP:Fe,Ru layers were grown on p-InP:Zn and n-InP:S substrates, in order to study dopant diffusion and electrical characteristics. Dopant diffusion profiles of Ru, Fe and Zn were measured by secondary ion mass spectroscopy. A small but noteworthy diffusion front is observed when InP:Ru is adjacent to InP:Zn, but not when adjacent to n-InP. For InP:Fe codoped with Ru a pronounced interdiffusion of Fe and Zn is observed for Ru concentrations less than 2 X 10(17) cm(-3), but, for a higher Ru concentration the interdiffusion is clearly suppressed. Moreover, when InP is codoped with Fe and Ru, the small diffusion tail of Ru in InP:Zn vanishes. Unlike InP:Fe, resistivities above 1 X 10(8) Ohm cm are measured for both electron and hole-current injection in InP:Fe,Ru.
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| 5. |
- Soderstrom, D., et al.
(författare)
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Electrical characterization of ruthenium-doped InP grown by low pressure hydride vapor phase epitaxy
- 2001
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Ingår i: Electrochemical and solid-state letters. - 1099-0062 .- 1944-8775. ; 4:6, s. G53-G55
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial layers of ruthenium-doped InP grown by low-pressure hydride vapor phase epitaxy have been studied. Current voltage measurements were conducted at temperatures between 20 and 200 degreesC for samples doped with Ru in the range 1 x 10(17) to 5 X 10(17) cm(-3). In this doping range, the specific resistivity of n(+)/InP:Ru/n(+) structures accommodating electron injection is less than or equal to1 x 10(4) Ohm cm and that of p(+)/InP:Ru/p(+) structures accommodating hole injection is as high as 3 x 10(10) Ohm cm. The reason for such a huge difference in the resistivity of these structures is attributed to a low activation of deep Ru acceptors, thus rather giving rise to an n(-) layer than a semi-insulating layer, as supported by our theoretical simulation. Analysis of the Arrhenius plots constructed from the temperature-dependent I-V curves yield an average activation energy of Ru with reference to the conduction band equal to 0.44 and 0.52 eV under electron and hole injection, respectively.
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| 6. |
- Soderstrom, D., et al.
(författare)
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Studies on ruthenium-doped InP growth by low-pressure hydride vapor-phase epitaxy
- 2001
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 148:7, s. G375-G378
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Tidskriftsartikel (refereegranskat)abstract
- Ruthenium-doped InP (InP:Ru) has been grown by low-pressure hydride vapor-phase epitaxy (LP-HVPE) using bis(eta (5)-2,4-dimethylpentadienyl)ruthenium(II) as precursor. Ruthenium concentrations in the range 2 x 10(15) to 2 x 10(18) cm(-3) have been achieved. The Ru incorporation has been studied in terms of incorporation flux, and it is shown that the growth rate limits: the incorporation rate. From current-voltage measurements on n-InP/InP:Ru/n-InP and p-InP/InP:Ru/p-InP structures, resistivities greater than 10(3) Omega cm and greater than 10(10) Omega cm have been obtained, respectively.
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| 7. |
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| 8. |
- Sun, Y. T., et al.
(författare)
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Temporally resolved selective area growth of InP in the openings off-oriented from 110 direction
- 2001
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Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 225:1, s. 9-15
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Tidskriftsartikel (refereegranskat)abstract
- Temporally resolved selective area growth of InP on patterned substrates with openings off-oriented from [110] direction was studied by low pressure hydride vapour phase epitaxy system. Lateral overgrowth and vertical growth were analysed. The lateral growth rate was observed to be strongly dependent on the orientation of the openings. The maximum lateral growth rate was achieved when the openings oriented at 30 degrees and 60 degrees off [110] direction. The vertical growth rate was relatively constant, independent of the opening orientation. The growth behaviour of InP in openings aligned at low index directions was explained by dangling bond theory. A new phenomenon of inhomogeneous and orientation dependent dopant distribution within an overgrown layer was observed in stained cross-sections by SEM.
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| 9. |
- Fox, A, et al.
(författare)
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Increased levels of bacterial markers and CO2 in occupied school rooms
- 2003
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Ingår i: Journal of Environmental Monitoring. - : Royal Society of Chemistry (RSC). - 1464-0325 .- 1464-0333. ; 5:2, s. 246-252
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Tidskriftsartikel (refereegranskat)abstract
- Our group previously demonstrated that carbon dioxide (CO2) levels in heavily occupied schools correlate with the levels of airborne bacterial markers. Since CO2 is derived from the room occupants, it was hypothesized that in schools, bacterial markers may be primarily increased in indoor air because of the presence of children: directly from skin microflora or indirectly, by stirring up dust from carpets and other sources. The purpose of this project was to test the hypothesis. Muramic acid (Mur) is found in almost all bacteria whereas 3-hydroxy fatty acids (3-OH FAs) are found only in Gram-negative bacteria. Thus Mur and 3-OH FA serve as markers to assess bacterial levels in indoor air (pmol m-3). In our previous school studies, airborne dust was collected only from occupied rooms. However, in the present study, additional dust samples were collected from the same rooms each weekend when unoccupied. Samples were also collected from outside air. The levels of dust, Mur and Cu-10:0, C-12:0, C-14:0, and C-16:0 3-OH FAs were each much higher (range 5 50 fod) in occupied rooms than in unoccupied school rooms. Levels in outdoor air were much lower than that of indoor air from occupied classrooms and higher than the levels in the same rooms when unoccupied. The mean CO2 concentrations were around 420 parts per million (ppm) in unoccupied rooms and outside air: and they ranged from 1017 to 1736 ppm in occupied rooms, regularly exceeding 800-1000 ppm, which are the maximum levels indicative of adequate indoor ventilation. This indicates that the children were responsible for the increased levels of bacterial markers. However, the concentration of Mur in dust was also 6 fold higher in occupied rooms (116.5 versus 18.2 pmole mg(-1)). This further suggests that airborne dust present in occupied and unoccupied rooms is quite distinct. In conclusion in unoccupied rooms, the dust was of environmental origin but the children were the primary source in occupied rooms.
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| 10. |
- Månsson, Martin, et al.
(författare)
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A new structural type for Haemophilus influenzae lipopolysaccharide : Structural analysis of the lipopolysaccharide from nontypeable Haemophilus influenzae strain 486
- 2001
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Ingår i: European Journal of Biochemistry. - : Wiley. - 0014-2956 .- 1432-1033. ; 268:7, s. 2148-2159
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Tidskriftsartikel (refereegranskat)abstract
- Structural elucidation of the sialylated lipopolysaccharide (LPS) of non-typeable Haemophilus influenzae (NTHi) strain 486 has been achieved by the application of high-field NMR techniques and ESI-MS along with composition and linkage analyses on O-deacylated LPS and oligosaccharide samples. It was found that the LPS contains the common element of H. influenzae, L-alpha -D-Hepp-(1-->2)][PEtn-->6]-L-alpha -D-Hepp-(1-->3)-[beta -D-Glcp-( 1-->4)]-L-alpha -D-Hepp-(1-->5)- [PPEtn-->4]-alpha -Kdop- (2-->6)-Lipid A, but instead of glycosyl substitution of the terminal heptose residue (HepIII) at the O2 position observed in other H. influenzae strains, HepIII is chain elongated at the O3 position by either lactose or sialyllactose (i.e. alpha -Neu5Ac(2-->3)-beta -D-Galp-(1-->4)-beta -D-Glcp). The LPS is substituted by an O-acetyl group linked to the O2 position of HepIII and phosphocholine (PCho) which was located at the O6 position of a terminal alpha -D-Glcp, residue attached to the central heptose, a molecular environment different from what has been reported earlier for PCho. In addition, minor substitution by O-linked glycine to the LPS was observed. By investigation of LPS from a lpsA mutant of NTHi strain 486, it was demonstrated that the lpsA gene product also is responsible for chain extension from HepIII in this strain. The involvement of lic1 in expression of PCho was established by investigation of a lic1 mutant of NTHi strain 486.
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