| 1. |
- Smith, Anderson D., et al.
(författare)
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Graphene-based CO2 sensing and its cross-sensitivity with humidity
- 2017
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:36, s. 22329-22339
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Tidskriftsartikel (refereegranskat)abstract
- We present graphene-based CO2 sensing and analyze its cross-sensitivity with humidity. In order to assess the selectivity of graphene-based gas sensing to various gases, measurements are performed in argon (Ar), nitrogen (N-2), oxygen (O-2), carbon dioxide (CO2), and air by selectively venting the desired gas from compressed gas bottles into an evacuated vacuum chamber. The sensors provide a direct electrical readout in response to changes in high concentrations, from these bottles, of CO2, O-2, nitrogen and argon, as well as changes in humidity from venting atmospheric air. From the signal response to each gas species, the relative graphene sensitivity to each gas is extracted as a relationship between the percentagechange in graphene's resistance response to changes in vacuum chamber pressure. Although there is virtually no response from O-2, N-2 and Ar, there is a sizeable cross-sensitivity between CO2 and humidity occurring at high CO2 concentrations. However, under atmospheric concentrations of CO2, this cross-sensitivity effect is negligible - allowing for the use of graphene-based humidity sensing in atmospheric environments. Finally, charge density difference calculations, computed using density functional theory (DFT) are presented in order to illustrate the bonding of CO2 and water molecules on graphene and the alterations of the graphene electronic structure due to the interactions with the substrate and the molecules.
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| 2. |
- Smith, Anderson D., et al.
(författare)
-
Graphene-based CO2 sensing and its cross-sensitivity with humidity
- 2017
-
Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 7:36, s. 22329-22339
-
Tidskriftsartikel (refereegranskat)abstract
- We present graphene-based CO2 sensing and analyze its cross-sensitivity with humidity. In order to assess the selectivity of graphene-based gas sensing to various gases, measurements are performed in argon (Ar), nitrogen (N2), oxygen (O2), carbon dioxide (CO2), and air by selectively venting the desired gas from compressed gas bottles into an evacuated vacuum chamber. The sensors provide a direct electrical readout in response to changes in high concentrations, from these bottles, of CO2, O2, nitrogen and argon, as well as changes in humidity from venting atmospheric air. From the signal response to each gas species, the relative graphene sensitivity to each gas is extracted as a relationship between the percentage-change in graphene's resistance response to changes in vacuum chamber pressure. Although there is virtually no response from O2, N2 and Ar, there is a sizeable cross-sensitivity between CO2 and humidity occurring at high CO2 concentrations. However, under atmospheric concentrations of CO2, this cross-sensitivity effect is negligible – allowing for the use of graphene-based humidity sensing in atmospheric environments. Finally, charge density difference calculations, computed using density functional theory (DFT) are presented in order to illustrate the bonding of CO2 and water molecules on graphene and the alterations of the graphene electronic structure due to the interactions with the substrate and the molecules.
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| 3. |
- Smith, Anderson D., et al.
(författare)
-
Resistive graphene humidity sensors with rapid and direct electrical readout
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 7:45, s. 19099-19109
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate humidity sensing using a change of the electrical resistance of single-layer chemical vapor deposited (CVD) graphene that is placed on top of a SiO2 layer on a Si wafer. To investigate the selectivity of the sensor towards the most common constituents in air, its signal response was characterized individually for water vapor (H2O), nitrogen (N-2), oxygen (O-2), and argon (Ar). In order to assess the humidity sensing effect for a range from 1% relative humidity (RH) to 96% RH, the devices were characterized both in a vacuum chamber and in a humidity chamber at atmospheric pressure. The measured response and recovery times of the graphene humidity sensors are on the order of several hundred milliseconds. Density functional theory simulations are employed to further investigate the sensitivity of the graphene devices towards water vapor. The interaction between the electrostatic dipole moment of the water and the impurity bands in the SiO(2)d substrate leads to electrostatic doping of the graphene layer. The proposed graphene sensor provides rapid response direct electrical readout and is compatible with back end of the line (BEOL) integration on top of CMOS-based integrated circuits.
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| 4. |
- Anderhag, Per, et al.
(författare)
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Why Do Secondary School Students Lose Their Interest in Science? Or Does it Never Emerge? A Possible and Overlooked Explanation
- 2016
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Ingår i: Science Education. - : Wiley. - 0036-8326 .- 1098-237X. ; 100:5, s. 791-813
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we review research on how students' interest in science changes through the primary to secondary school transition. In the literature, the findings generally show that primary students enjoy science but come to lose interest during secondary school. As this claim is based mainly on interview and questionnaire data, that is on secondary reports from students about their interest in science, these results are reexamined through our own extensive material from primary and secondary school on how interest is constituted through classroom discourse. Our results suggest the possibility that primary students do not lose their interest in science, but rather that an interest in science is never constituted. The overview indicates that studies relying on interviews and questionnaires make it difficult to ascertain what the actual object of interest is when students act in the science classroom. The possibility suggested should, if valid, have consequences for science education and be worthy of further examination.
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| 5. |
- Andersson, Joel B. H., et al.
(författare)
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Structural controls on sulphide (re)-distribution in Kiruna
- 2019
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Ingår i: Proceedings of the 15th SGA Biennial Meeting, 27-30 August. - : University of Glasgow Publicity Services. ; , s. 115-118
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Konferensbidrag (refereegranskat)abstract
- In this study, we investigate a potential structural control on sulphide distribution in phyllite from the Kiruna area, northern Norrbotten, Sweden. We use X-ray tomography and X-ray fluorescence analyzed in tandem on a 40 cm section of oriented drill core. Scanning Electron Microscopy and Energy Dispersive Spectrometry are used in combination with optical microscopy to analyze mineralogy and microstructures. The results show that sulphides are distributed along So bedding planes, re-distributed along S-2 axial planar cleavage planes, and trapped by F-2-hinge zones and shear bands visible as elevated sulphide concentrations. The results of this study underlines the strength of X-ray tomography to image 3D geological structures and their relation to mineral distributions.
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| 6. |
- Andersson, Åke, et al.
(författare)
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Status of the new injector for MAX-lab
- 2002
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Ingår i: 8th European Particle Accelerator Conference. ; , s. 772-774
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Konferensbidrag (refereegranskat)abstract
- The new injector for MAX-lab is built around two 125 MeV linacs [B. Anderberg, (2000)] equipped with SLED cavities [Z.D. Farkas, (1974)]. The electron beam is recirculated once to reach 500 MeV. A 2.3 MeV thermionic RF gun [B. Anderberg, (2000)] injects into the system. The RF-gun is put into operation and commissioning of the first linac is proceeding. Results from the thermionic RF-gun operation, linac commissioning and first beam operations are presented.
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| 7. |
- Andersson, Åke, et al.
(författare)
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The 100 MHz RF system for MAX-II and MAX-III
- 2002
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Ingår i: 8th European Particle Accelerator Conference. ; , s. 2118-2120
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Konferensbidrag (refereegranskat)abstract
- The MAX-II synchrotron radiation source has since 1997 been operated routinely with a double RF system, 500 MHz active plus 1.5 GHz passive. Four Landau cavities have successfully provided increased Touschek beam lifetime, and damping of coupled bunch mode instabilities. However, the delivered power from the present 500 MHz RF system will be marginal for the operation of the planned MAX-II SC wigglers, with 250 mA circulating beam current. It is shown that it is favourable to change to a 100 MHz system, with one 500 MHz Landau cavity, both considering power consumption, beam lifetime and beam stability. The new RF system and the cavities, that are being built at MAX-lab, are described. The same RF combination and type of cavities will be used at the VUV source MAX-III
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| 8. |
- Axenrot, Thomas; Bergqvist, Björn; Carlstein, Mikael; Degerman, Erik,
(författare)
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Fiskundersökningar i större vattendrag
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- De större vattendragen (åar, älvar och floder) är ofta bristfälligtundersökta, trots att de ofta är kraftigt påverkade av mänskligaaktiviteter. Under senare år har behovet av undersökningari dessa vattendrag ökat eftersom EU:s ramdirektiv för vattenkräver övervakning av vattnens ekologiska status i alla typer avvatten. Det har också under senare förts fram önskemål om attkunna använda metoder som inte är destruktiva (dödande) vidkvantifi ering av fi skförekomsten i både sjöar och vattendrag.I syfte att utveckla icke dödande metoder för kvantitativafi skundersökningar i större vattendrag har under åren 2005och 2006 ett pilotprojekt omfattande både båtelfi ske ochhydroakustiska metoder (mobil horisontell ekolodning)genomförts i vattendragen Österdalälven (Älvdalens kommun)och Svartån (Örebro kommun). Projektet har genomförts som ettsamarbetsprojekt mellan Fiskeriverkets sötvattenslaboratorium,Systemekologiska institutionen vid Stockholms Universitet ochF.A.S.T. – Fiskeresursgruppen vid Älvdalens utbildningscentrum.Projektet har genomförts som ett utvecklingsprojekt inommiljöövervakningsprogrammet och har fi nansierats avNaturvårdsverkets Miljöövervakningsenhet.Arbetet har genomförts med målsättningen att metodiken skallvara tillämpbar för såväl övervakning av fi skresurserna somför miljöövervakning och bedömning av ekologisk status enligtramdirektivets krav. Dessutom skall metodiken kunna användasför uppföljning av de nationella miljökvalitetsmålen. Villkorsom måste uppfyllas är att metoderna skall ge informationom fi skbeståndens sammansättning, individtäthet ochstorleksfördelning utan att fi sken behöver dödas.I denna rapport redovisas resultatet av undersökningarna ochen jämförelse av de båda testade metoderna (båtelfi ske ochekolodning), dessutom ges rekommendationer för framtidaundersökningar i större vattendrag. Avsikten är att rapporten skallutgöra plattform för arbetet med att ta fram en standardiseradmetodik för undersökningar i större vattendrag som inte ärvadbara.
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| 9. |
- Bergqvist, Cecilia, et al.
(författare)
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Multiplex Nucleic Acid Suspension Bead Arrays for Detection and Subtyping of Filoviruses
- 2015
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Ingår i: Journal of Clinical Microbiology. - 0095-1137 .- 1098-660X. ; 53:4, s. 1368-1370
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Tidskriftsartikel (refereegranskat)abstract
- Here we describe multiplex suspension bead array systems that allow fast and reliable detection of reverse transcriptase (RT) PCR amplified filovirus genomes and also enable subtyping of Ebola virus species and Marburg virus strains. These systems have an analytical sensitivity equivalent to that of RT-PCR.
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| 10. |
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