| 1. |
- Andersson, Patrik, 1974, et al.
(författare)
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Framtidsbilder för samhällsbyggnad
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Framtidsbilder för samhällsbyggnad 2020De kommande 15 åren står institutionen för Bygg- och miljöteknik inför stora förändringar. Därför har institutionen initierat projektet Framtidsbilder 2020 där man engagerat en framtidspanel bestående av elva yngre disputerade forskare. Arbetet inleddes med ett breddgruppsmöte där 110 personer representerande institutionens personal och studenter deltog. Vid mötet identifierades ett antal trender och osäkra utvecklingar som påverkar framtiden inom samhällsbyggnadsområdet. Deltagarna bidrog också med idéer till en önskvärd utveckling, vilket har sammanställts och utgör grunden till en gemensam önskvärd framtid/vision för institutionen. Materialet från breddgruppsmötet har bearbetats av Framtidspanelen och resulterat i fyra scenarier som beskriver hur samhällsbyggnadsområdet kan se ut år 2020. Syftet med framtidsbilderna är att de ska vara vägledande för institutionens beslut och förhållningssätt under de kommande åren.Fyra scenarierTurning TorsoSamhället präglas av en ekonomi som är på uppgång, och av ett nytänkande och öppet samhälle. Materiell status och individualism är viktigt. Detta leder till en hög arbetsbelastning samt krav på exklusiva varor av hög kvali-tet. Det finns en stor medvetenhet om miljöpåverkan och klimatförändringar och lösningarna för att klara energiförsörjningen är innovativa.Eco-metropolenDet sveper en grön våg genom dagens samhälle. Under de senaste 15 åren har vi insett att jorden skall vara en bebolig plats även åt dem som kommer efter oss. Vi söker ständigt efter nya, mer förfinade metoder att tillvarata de resurser vi har. Samhället och individen är i balans. Ekonomin är god och vi är miljömedvetna, trygga och integrerade. Nytänkande premieras och icke- materialistiska värderingar står högt i kurs. Vi tänker individuellt, men agerar mer än gärna för kollektivets bästa. Utbildning är gratis TrädgårdsstadenEtt samhälle där vi lärt oss hantera stress, men känner oss otrygga och helst umgås i slutna sociala sammanhang. Vi bor enkelt inne i stan, eller gärna på landsbygden nära storstäderna. Minskade behov av högutbildade i samhället gör att vi har svårt att rekrytera studenter till teknikutbildningar. Det traditionella tankesättet leder till kulturkrockar med företag och personer från andra länder.Gated communitiesFörsämrad ekonomi och ökad egoism har lett fram till ett stressat, otryggt och segregerat samhälle. Accelererande klimatförändringar och ökad miljö-påverkan skrämmer oss, men trots det åtgärdar vi inte problemen, utan koncentrerar oss på konsekvenserna. Arbetslöshet i samhällsbyggnadssek-torn leder till sänkt status för samhällsbyggaren. Vi har därför svårt att rekrytera studenter, och även forskningen har låg status.
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| 2. |
- Andersson, Pontus, 1971, et al.
(författare)
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Isobar Selective Laser Photodetachment In Trace Element Analysis
- 2009
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Ingår i: AIP Conference Proceedings. ; 1104
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Konferensbidrag (refereegranskat)abstract
- We are investigating the possibility to use laser photodetachment of negative ions as an isobaric selective filter in accelerator mass spectrometry (AMS). If successful, this method can be used to obtain higher sensitivity realized through better selectivity by suppression of molecular and/or elemental isobaric interference in different investigations using ultra rare isotopes in the 10−13 range and below.
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| 3. |
- Andersson, Pontus, 1971
(författare)
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Laser Photodetachment of Negative Ions - Fundamental Research and Applications
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Photodetachment studies of atomic and molecular negative ions in the gas phase are presented. Negative ions are loosely bound quantum systems whose existence is strongly dependent on the correlations between the electrons. This makes sophisticated calculations of the structure and dynamics for these systems complex and experimental data are needed for verification. Negative ions are also important in applications such as plasma etching and atmospheric studies. One of the most important applications for negative ions is as the state of matter for injection in tandem accelerators used in Accelerator Mass Spectrometry (AMS), the most sensitive method for ultra trace isotope analysis. Using negative ions in the injection stage provides isobar suppression in cases where the contaminating isobar does not form stable negative ions. Several experiments on laser interaction with a beam of mass-selected negative ions are presented. The objective for these studies can be divided into three subgroups: structure studies, dynamic studies, and proof-of-principle experiments for applications of negative ions. In the first group, the value for the electron affinity and the fine structure splitting of phosphorus is refined. The value of the electron affinity of tungsten is improved and the origin of the photodetachment signal below threshold is discussed. Resonant structure in the cross section and the electron affinity of cerium is treated. Finally, a predicted excited state in platinum is observed experimentally for the first time. The second group consists of the lifetime measurements of metastable excited states for tellurium, selenium and silicon. These measurements were made at the magnetic heavy ion storage ring CRYRING at Manne Siegbahn Laboratories in Stockholm. The third and last group are proof-of-principle experiments of isobar and neighboring isotope suppression by laser interaction. Suppression of up to four orders of magnitude is reached and the implementation into mass spectrometric systems are discussed.
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| 4. |
- Andersson, Pontus, 1971, et al.
(författare)
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Nearly complete isobar suppression by photodetachment
- 2010
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 1089-7550 .- 0021-8979. ; 107:2
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Tidskriftsartikel (refereegranskat)abstract
- The efficiency of selective suppression of negative ions by photodetachment in a gas-filled radio frequency quadrupole ion cooler was investigated with a new detection method. A neodymium doped yttrium aluminum garnet laser beam at 1064 nm was used to remove Co− ions in the radio frequency quadrupole cooler and the remaining ions were then probed by photodetachment and neutral particle detection. More than 99.99% suppression of the Co− ions was observed. Under identical conditions, only 20% of a Ni− beam was suppressed. The results demonstrate that this isobar suppression technique can lead to nearly complete elimination of certain isobaric contaminants in negative ion beams, opening up new experimental possibilities in nuclear and atomic research and accelerator mass spectrometry.
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| 5. |
- Andersson, Pontus, 1971, et al.
(författare)
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Observation of the 2S1/2 metastable state in Pt−
- 2009
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Ingår i: PHYSICAL REVIEW A. - 1050-2947. ; 79, s. 022502 -
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Tidskriftsartikel (refereegranskat)abstract
- We have experimentally investigated the structure of the Pt− ion using laser photodetachment threshold spectroscopy. The experiment was conducted using a collinear laser-ion beam apparatus, in which the residual atoms created in the photodetachment process were detected. A p-wave threshold was observed in the photo- detachment spectrum at an energy of 6851͑13͒ cm−1. We conclude that this onset originates from a photode- tachment transition in which the initial state of Pt− is the previously unobserved 5d106s 2S1/2 state and the final state of Pt is the 5d96s 3D3 ground state. The excitation energy of the 2S1/2 state is determined to be 10 289͑13͒ cm−1. This value can be compared with a multiconfiguration Dirac-Fock calculation performed by Thøgersen et al. ͓Phys. Rev. Lett. 76, 2870 ͑1996͔͒, which yielded an excitation energy of 11 301 cm−1. Our data show no indication of the presence of any other state of Pt−. We conclude that the structure of the Pt− ion is now fully known.
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| 6. |
- Andersson, Pontus, 1971, et al.
(författare)
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Radiative lifetimes of metastable states of negative ions
- 2006
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705-
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Tidskriftsartikel (refereegranskat)abstract
- We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
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| 7. |
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| 8. |
- Andersson, Pontus, 1971, et al.
(författare)
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The electron affinity of phosphorus
- 2007
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Ingår i: Journal of Physics B-Atomic Molecular and Optical Physics. ; 40:20, s. 4097-4107
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Tidskriftsartikel (refereegranskat)
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| 9. |
- Bergemalm, Daniel, 1977-, et al.
(författare)
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Markers of systemic inflammation in preclinical ulcerative colitis
- 2019
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Ingår i: United European Gastroenterology journal. - : Sage Publications. - 2050-6406 .- 2050-6414. ; 7:8_suppl, s. 111-111
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Data on the preclinical stage of ulcerative colitis (UC) are sparse. At diagnosis, UC often shows a modest increase in systemic inflammatory markers like C-reactive protein (CRP). However, a subclinical inflammation with elevated levels of CRP and interleukin-6 (IL6) in serum have been observed several years before diagnosis [1]. First-degree relatives, including healthy twin siblings, also display elevated levels of some inflammatory markers as a consequence of shared genetic and environmental risk factors [2]. It is reasonable to believe that the preclinical inflammation, reflecting early pathogenic mechanisms, ultimately leads to a diagnosis of UC.Aim and Method: We aimed to deeper examine the systemic preclinical inflammation in UC using a comprehensive set of protein markers. Cases with UC were identified at clinical follow-up of a prospectively collected population-based cohort of healthy individuals from northern Sweden. Plasma samples from cases and controls were subjected to proximity extension assay for relative quantification of 92 protein markers of inflammation. Results were validated in an inception cohort of treatment naïve, newly diagnosed patients with UC (n=101) vs. healthy controls (n=50). In addition, to examine the impact of shared genetic and environmental factors, a cohort of healthy mono- and dizygotic twin siblings of twins with UC (n=41) and matched healthy controls (n=37) were explored.Results: Pre-diagnostic plasma samples from 72 cases who later in life developed UC and 140 controls, matched for gender, age, year of health survey and area of residence, were identified (table 1). Six proteins were significantly upregulated (p<0.05) in pre-diagnostic UC compared to matched healthy controls. A receiver-operating curve based prediction model using the six protein markers combined with sex, age, smoking status and time to diagnose was set up for validation. The model discriminated newly diagnosed, treatment naïve UC cases from healthy controls (AUC=0.96; CI 0.93-0.98). An AUC of 0.73 (CI 0.62-0.84) was observed when the model was applied to healthy twin siblings vs. healthy controls and four out of six proteins were upregulated similarly as in the pre-diagnostic samples. The relative levels of the six proteins showed an intermediate upregulation in pre-diagnostic samples and samples from healthy twin siblings compared to samples at diagnosis of UC. Only one protein showed a significant correlation with time to diagnosis in the pre-diagnostic samples. Using pathway analysis, the six protein upregulations pointed towards subclinical inflammation in UC being caused by dysregulation of four immune pathways.Conclusions: This is the first comprehensive characterisation of preclinical systemic inflammation in UC. Inflammatory proteins were upregulated several years prior to diagnosis of UC and to some extent these alterations were also seen in healthy twin siblings of UC patients. Characterisation of the preclinical stage of UC could pave the way for identification of predictive biomarkers and preventive strategies.
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| 10. |
- Bergemalm, Daniel, 1977-, et al.
(författare)
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Systemic Inflammation in Preclinical Ulcerative Colitis
- 2021
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Ingår i: Gastroenterology. - : AGA Institute. - 0016-5085 .- 1528-0012. ; 161:5, s. 1526-1539.e9
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Tidskriftsartikel (refereegranskat)abstract
- Background & Aims: Preclinical ulcerative colitis is poorly defined. We aimed to characterize the preclinical systemic inflammation in ulcerative colitis, using a comprehensive set of proteins.Methods: We obtained plasma samples biobanked from individuals who developed ulcerative colitis later in life (n = 72) and matched healthy controls (n = 140) within a population-based screening cohort. We measured 92 proteins related to inflammation using a proximity extension assay. The biologic relevance of these findings was validated in an inception cohort of patients with ulcerative colitis (n = 101) and healthy controls (n = 50). To examine the influence of genetic and environmental factors on these markers, a cohort of healthy twin siblings of patients with ulcerative colitis (n = 41) and matched healthy controls (n = 37) were explored.Results: Six proteins (MMP10, CXCL9, CCL11, SLAMF1, CXCL11 and MCP-1) were up-regulated (P < .05) in preclinical ulcerative colitis compared with controls based on both univariate and multivariable models. Ingenuity Pathway Analyses identified several potential key regulators, including interleukin-1β, tumor necrosis factor, interferon-gamma, oncostatin M, nuclear factor-κB, interleukin-6, and interleukin-4. For validation, we built a multivariable model to predict disease in the inception cohort. The model discriminated treatment-naïve patients with ulcerative colitis from controls with leave-one-out cross-validation (area under the curve = 0.92). Consistently, MMP10, CXCL9, CXCL11, and MCP-1, but not CCL11 and SLAMF1, were significantly up-regulated among the healthy twin siblings, even though their relative abundances seemed higher in incident ulcerative colitis.Conclusions: A set of inflammatory proteins are up-regulated several years before a diagnosis of ulcerative colitis. These proteins were highly predictive of an ulcerative colitis diagnosis, and some seemed to be up-regulated already at exposure to genetic and environmental risk factors.
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| 11. |
- Bilodeau, R. C., et al.
(författare)
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High-charge-state formation following inner-shell photodetachment from S-
- 2005
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Ingår i: Physical Review A. - 1050-2947. ; 72, s. 050701-
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Tidskriftsartikel (refereegranskat)abstract
- The formation of S+, S2+, S3+, and S4+ is observed following inner-shell photodetachment of S–. The photodetachment spectra for all possible ionic products are obtained over a large region of photon energies covering both the 2p and 2s thresholds (S5+, is energetically allowed at the higher photon energies, but not observed), and are placed on an absolute scale. The 2s threshold energy is measured to be 224.6(5) eV, allowing the determination of the neutral atomic S 2s–13s23p5 inner-shell excited state energy for the first time. The S– 2s–13s23p6 2S1/2 state is observed as a Feshbach resonance 2.3(5) eV below the 2s threshold in the S+, S2+, and S3+ product channels.
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| 12. |
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| 13. |
- Diehl, C., et al.
(författare)
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Ion optical design of a collinear laser-negative ion beam apparatus
- 2011
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Ingår i: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 82:5
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Tidskriftsartikel (refereegranskat)abstract
- An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ≃ 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M/ΔM≅800 for molecular ions and M/ΔM≅400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.
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| 14. |
- Ellmann, A, et al.
(författare)
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Radiative lifetime of a bound excited state of Te-
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:25, s. 253002-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) P-2(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.
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| 15. |
- Falk Erhag, Hanna, et al.
(författare)
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Concluding Remarks
- 2022
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Ingår i: A Multidisciplinary Approach to Capability in Age and Ageing. - Chem : Springer. - 9783030780654 ; 18:2, s. 143-144
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 16. |
- Forstner, O., et al.
(författare)
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Isobar suppression in AMS using laser photodetachment
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. ; 266:19-20, s. 4565-4568
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Tidskriftsartikel (refereegranskat)abstract
- We are investigating the possibility of using laser photodetachment of negative atomic and molecular ions as an additional isobaric selection filter in accelerator mass spectrometry. The aim of this study is to find a possibility to further improve the detection limit for long-lived heavy radionuclides at AMS facilities. We will focus on the astrophysical relevant radionuclide 182Hf, which is one of the isotopes measured with the 3 MV tandem AMS facility VERA (Vienna Environmental Research Accelerator) at the University of Vienna. Laser-induced isobar suppression is also of importance for radioactive-beam facilities. The present detection limit for measuring the isotope ratio 182Hf/Hf at VERA is 1×10-11. The limiting factor is the strong background of the stable isobar 182W. Currently this background is suppressed using suitable molecular ions in the injection stage. Selective laser photodetachment of the negative ions at the injector can lead to an additional suppression of the interfering isobar. Test experiments have been carried out at the negative ion laser spectroscopy setup at Göteborg University. In a small ion beam apparatus pulsed tunable laser radiation is used to measure the photodetachment cross-section of different atomic and molecular negative ions. We will present studies of the photodetachment process for various tungsten and hafnium molecules with the aim to find a selective isobaric suppression scheme using laser photodetachment spectroscopy in combination with AMS.
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| 17. |
- Forstner, O., et al.
(författare)
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The ILIAS project for selective isobar suppression by laser photodetachment
- 2015
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 361, s. 217-221
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Tidskriftsartikel (refereegranskat)abstract
- Laser photodetachment is the process when the extra electron of a negative ion is removed by means of laser radiation. This can happen only if the photon energy is larger than the electron affinity of the ion. The process can be used in mass spectrometry to selectively suppress unwanted isobars, provided that the electron affinity of the unwanted isobar is lower than that of the isobar under investigation.At the Ion Laser InterAction Setup (ILIAS) at the University of Vienna laser photodetachment of negative atomic and molecular ions is studied and its applicability for selective isobar suppression in accelerator mass spectrometry (AMS) is evaluated. The setup provides mass separated beams of negative ions with energies up to 30 keV. Negative ions are produced in a Middleton type cesium sputter ion source, mass selected and overlapped with a strong continuous wave laser beam. In order to extend the interaction time of ions and laser, the ion beam is decelerated to thermal energies in a gas-filled radio frequency quadrupole cooler. For an appropriate choice of the photon energy, unwanted isobars are neutralized while the isobar of interest is unaffected and remains negatively charged.A description of the ILIAS setup and results from the commissioning phase of the RFQ cooler are presented. Up to 8% ion beam transmission could be achieved after a recent redesign of the extraction system. Furthermore first results of photodetachment experiments of 63Cu− within the RFQ cooler are presented.
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| 18. |
- Fritioff, Karin, et al.
(författare)
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Observation of an excited C2-4 ion
- 2004
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:11, s. 2241-2246
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports an experimental investigation of the electron impact detachment of C−4. We observe structure in the electron impact cross section for detaching a single electron from a C−4 cluster anion, which we attribute to the formation and decay of the C2−4 dianion. The system is energetically unstable and very rapidly decays via double autodetachment. The energy and width of the resonance were determined to be 8.8(5) eV and 1.4(5) eV, respectively, and the resonance lies 1.5(5) eV above the ground state of the neutral system. The experiment was conducted by merging monoenergetic electron and ion beams in the heavy ion storage ring CRYRING. The detachment channel was monitored by detecting neutral C4 fragments.
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| 19. |
- Fritioff, K, et al.
(författare)
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Single and double detachment from H-
- 2004
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Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 69:4, s. 042707-
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Tidskriftsartikel (refereegranskat)abstract
- Absolute cross sections for single and double detachment from H- following electron impact have been measured over a range of collision energies from the thresholds to 170 eV. The measurements were made using a magnetic storage ring. The ions in the ring were merged with a monoenergetic electron beam and neutral and positively charged fragments were detected. We cover larger energy ranges than in many of the previous experiments, and this is the first time both single and double detachment have been measured simultaneously. This allows us to present accurate ratios between the single and double detachment cross sections. On the basis of these ratio measurements we discuss possible mechanisms leading to double detachment.
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| 20. |
- James, Stefan, 1964-, et al.
(författare)
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Bivalirudin Versus Heparin Monotherapy in ST-Segment-Elevation Myocardial Infarction
- 2021
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Ingår i: Circulation. Cardiovascular Interventions. - : Lippincott Williams & Wilkins. - 1941-7640 .- 1941-7632. ; 14:12
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Bivalirudin was not superior to unfractionated heparin in patients with myocardial infarction (MI) treated with percutaneous coronary intervention and no planned use of GPI (glycoprotein IIb/IIIa inhibitors) in contemporary clinical practice of radial access and potent P2Y12-inhibitors in the VALIDATE-SWEDEHEART randomized clinical trial (Bivalirudin Versus Heparin in STEMI and NSTEMI Patients on Modern Antiplatelet Therapy-Swedish Web-System for Enhancement and Development of Evidence-Based Care in Heart Disease Evaluated According to Recommended Therapies Registry).METHODS: In this prespecified separately powered subgroup analysis, we included patients with ST-segment-elevation MI undergoing primary percutaneous coronary intervention with the primary composite end point of all-cause death, MI, or major bleeding event within 180 days.RESULTS: Among the 6006 patients enrolled in the trial, 3005 patients with ST-segment-elevation MI were randomized to receive bivalirudin or heparin. The mean age was 66.8 years. According to protocol recommendations, 87% were treated with potent oral P2Y12-inhibitors before start of angiography and radial access was used in 90%. GPI was used in 51 (3.4%) and 74 (4.9%) of patients randomized to receive bivalirudin and heparin, respectively. The primary end point occurred in 12.5% (187 of 1501) and 13.0% (196 of 1504; hazard ratio [HR], 0.95 [95% CI, 0.78-1.17], P=0.64) with consistent results in all major subgroups. All-cause death occurred in 3.9% versus 3.9% (HR, 1.00 [0.70-1.45], P=0.98), MI in 1.7% versus 2.2% (HR, 0.76 [0.45-1.28], P=0.30), major bleeding in 8.3% versus 8.0% (HR, 1.04 [0.81-1.33], P=0.78), and definite stent thrombosis in 0.5% versus 1.3% (HR, 0.42 [0.18-0.96], P=0.04).CONCLUSIONS: In patients with ST-segment-elevation MI undergoing primary percutaneous coronary intervention with radial access and receiving current recommended treatments with potent P2Y12-inhibitors rate of the composite of all-cause death, MI, or major bleeding was not lower in those randomized to receive bivalirudin as compared with heparin.REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT02311231.
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| 21. |
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| 22. |
- Lindahl, Anton, 1982, et al.
(författare)
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The electron affinity of tungsten
- 2010
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Ingår i: The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 60:2, s. 219-222
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Tidskriftsartikel (refereegranskat)abstract
- The electron affinity of tungsten has been measured using laser photodetachment threshold spectroscopy in a collinear geometry. The electron affinity was determined to 6583.6(6) cm-1 by observing the onset of the process when W- ions in the 6S5/2 ground state are photodetached producing neutral W atoms in the 5D0 ground state. The measured value is in agreement with previous measurements and improves the accuracy by almost two orders of magnitude. Further, a photodetachment signal below the ground state photodetachment threshold was found, which indicates the existence of a bound excited state in W-.
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| 23. |
- Martschini, Martin, et al.
(författare)
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Light induced suppression of sulfur in a cesium sputter ion source
- 2012
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Ingår i: International Journal of Mass Spectrometry. - : Elsevier BV. - 1387-3806. ; 315, s. 55-59
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Tidskriftsartikel (refereegranskat)abstract
- New techniques for suppression of atomic isobars in negative ion beams are of great interest for accelerator mass spectrometry (AMS). Especially small and medium-sized facilities can significantly extend their measurement capabilities to new interesting isotopes with a technique independent of terminal voltage. In a new approach, the effect of continuous wave laser light directed towards the cathode surface in a cesium sputter ion source of the Middleton type was studied. The laser light induced a significant change in oxygen, sulfur and chlorine negative ion production from a AgCl target. Approximately 100 mW of laser light reduced the sulfur to chlorine ratio by one order of magnitude. The effect was found to depend on laser power and ion source parameters but not on the laser wavelength. The time constant of the effect varied from a few seconds up to several minutes. Experiments were first performed at the ion beam facility GUNILLA at University of Gothenburg with macroscopic amounts of sulfur. The results were then reproduced at the VERA AMS facility with chemically cleaned AgCl targets containing ∼1 ppm sulfur. The physical explanation behind the effect is still unclear. Nevertheless, the technique has been successfully applied during a regular AMS measurement of 36Cl.
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| 24. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Measurements of fugitive emissions of vocs from stationary sources using the SOF method - Standardization efforts and results from recent studies in California
- 2019
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Ingår i: AQM 2019 - Air Quality Measurement Methods and Technology Conference 2019.
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Konferensbidrag (refereegranskat)abstract
- The Solar Occultation Flux (SOF) method is used to screen and quantify VOC emissions from industrial conglomerates down to sub-areas in individual plants, such as a few tank process area or water treatment areas. The SOF method has been applied in several larger campaigns in both Europe and in the US (Mexico City 2006, Texas 2006/2009/2011/2012; Le Havre 2008, Rotterdam 2008/2010 and Antwerp 2010/2016, California 2013/20T5, Tianjin China 2016) and in more than 100 individual plant surveys over the world. The technique has been validated by comparison to other methods and tracer gas releases and it typically has an uncertainty of 30%, mostly due to uncertainties in the wind field. In the various campaign studies it has been found that the measured emissions obtained with SOF are 3–10 times higher than the reported emission obtained by calculations. The SOF method is Best Available Technology in Europe for quantitative measurements of diffuse emissions from refineries and the chemical sector. The technique is presently being standardized by the European CEN.
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| 25. |
- Mellqvist, Johan, 1965, et al.
(författare)
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Methane emissions from industrial activities using drones
- 2023
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Innovative drone-based methods have been developed to map and quantify methane leakages from various industrial activities, such as refineries, Liquified Natural Gas (LNG) terminals, landfills, and water treatment facilities. These methods use a high-speed, high-sensitivity laser sensor and were validated through controlled gas releases. They were also compared to a ground-based infrared absorption-based technique. This initiative is supported by the Swedish Governmental Agency for Innovation Systems (Vinnova) and aligns with UN Sustainable Development Goals 9, 11, and 13. The goal is to reduce methane emissions significantly, aiding Sweden in achieving net-zero greenhouse gas emissions by 2045. Accurate measurements enable effective, targeted, and trackable measures to minimize emissions, resulting in a rapid positive climate impact. The project has led to the development of two distinct drone-based methods: the wall approach and the tracer approach. The wall approach measures gas concentrations across the entire cross-section of the plume, whereas the tracer approach measures the ratio of leaking gas to source gas. Depending on the source's size, one approach may be preferred over the other, with the tracer method being more suitable for point sources and the wall approach for larger sources. The custom-designed drone in this project, provided and operated by Gerdes Solution. is equipped with a high-sensitivity laser sensor and has a flight duration of about 12 minutes while carrying a 3 kg payload. This limitation presents a challenge when conducting wall measurements, which require approximately 25 minutes of flight time for the studied sources. Due to the drone's limited flight time, it necessitates landing and battery replacement, which complicates the process and limits the number of repeat measurements. In future endeavors, employing a drone with a longer flight duration would be advantageous. In total, the study detected about 220 kg/h of methane emissions and 3 kg/h of nitrous oxide emissions, equivalent to an emission rate of about 7 tons/h of carbon dioxide. The emissions were dominated by the water treatment plant and landfills, with relatively little coming from the refinery and LNG plant. However, the wall measurements in thus study serve as demonstrations of how the technique can be used and do not provide a comprehensive picture of the actual emissions from the individual sites; this would require more statistical data in terms of repeat measurements and measurement days. It is shown that drone measurements using the new high sensitivity laser is a valuable tool for mapping methane concentrations from various types of industrial sources, which are challenging to investigate today due to diffuse emissions, large dimensions, and complex geometries. The validation studies show that both the wall approach and controlled tracer releases can be used to quantify emissions, achieving an accuracy of up to 10 % for a simple, single, source. However, in the real measurement situation, the wall approach may be difficult to execute due to practical challenges like flying restrictions and the need for spatially dense data that can be interpolated to a homogenous grid and repeated measurements. In several cases, when the drone had to fly relatively close to the plumes, downwind of large buildings in complex and turbulent wind fields, the wall approach yielded large variability in the resulting flux. It is hence evident that the wall approach requires a thorough understanding of the measurement situation, and that repeated measurements are needed, at different distances from the source and in varying wind directions. The tracer approach was therefore preferred choice for obtaining emission rates in this study, although it is challenging to carry out representative tracer releases for larger sources and for cases when the measurements are performed near to the source, and in this case the wall approach is preferred. It was also shown that the drone-based tracer approach is advantageous to the ground based since it is then easier to capture the full plume.
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