| 1. |
- Abdellaoui, G., et al.
(författare)
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Meteor studies in the framework of the JEM-EUSO program
- 2017
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Ingår i: Planetary and Space Science. - : Elsevier. - 0032-0633 .- 1873-5088. ; 143, s. 245-255
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Tidskriftsartikel (refereegranskat)abstract
- We summarize the state of the art of a program of UV observations from space of meteor phenomena, a secondary objective of the JEM-EUSO international collaboration. Our preliminary analysis indicates that JEM-EUSO, taking advantage of its large FOV and good sensitivity, should be able to detect meteors down to absolute magnitude close to 7. This means that JEM-EUSO should be able to record a statistically significant flux of meteors, including both sporadic ones, and events produced by different meteor streams. Being unaffected by adverse weather conditions, JEM-EUSO can also be a very important facility for the detection of bright meteors and fireballs, as these events can be detected even in conditions of very high sky background. In the case of bright events, moreover, exhibiting some persistence of the meteor train, preliminary simulations show that it should be possible to exploit the motion of the ISS itself and derive at least a rough 3D reconstruction of the meteor trajectory. Moreover, the observing strategy developed to detect meteors may also be applied to the detection of nuclearites, exotic particles whose existence has been suggested by some theoretical investigations. Nuclearites are expected to move at higher velocities than meteoroids, and to exhibit a wider range of possible trajectories, including particles moving upward after crossing the Earth. Some pilot studies, including the approved Mini-EUSO mission, a precursor of JEM-EUSO, are currently operational or in preparation. We are doing simulations to assess the performance of Mini-EUSO for meteor studies, while a few meteor events have been already detected using the ground-based facility EUSO-TA.
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| 2. |
- Gopakumar, Geethanjali, 1992-, et al.
(författare)
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X-ray Induced Fragmentation of Protonated Cystine
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Protein structure determination using high-intensity X-ray sources induces damage in the protein. Disulfide bridges, formed between two cysteine amino acid residues stabilize the protein structure. Owing to the higher absorption cross-section of sulfur for X-ray photons, and a large number of electrons released from sulfur atoms, these disulfide bridges are hot spots for a higher level of noise in structural studies. But it is yet to be understood how exactly the damage occurs through the interaction of the disulfide bridges with photons. Here we study the fragmentation of protonated cystine in the gas phase, which is the dimer of cysteine, by irradiation with X-rays across the sulfur L-edge using an electrospray ionization source (ESI) in combination with an ion trap. This is complemented with the calculation of the sulfur NEXAFS spectrum on the level of Restricted Open-Shell Configuration Interaction (ROCIS) and Density Functional Theory (DFT) calculations for molecular orbital visualization as well as Molecular Dynamics (MD) simulations for the fragmentation of triply charged cystine ions. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons by combining the experiments and simulations. The disulfide bridge breaks for resonant excitation at lower energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments formed subsequently break into smaller fragments.
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| 3. |
- Gopakumar, Geethanjali, 1992-, et al.
(författare)
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X-ray Induced Fragmentation of Protonated Cystine
- 2022
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 126:9, s. 1496-1503
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate site-specific X-ray induced fragmentation across the sulfur L-edge of protonated cystine, the dimer of the amino acid cysteine. Ion yield NEXAFS were performed in the gas phase using electrospray ionization (ESI) in combination with an ion trap. The interpretation of the sulfur L-edge NEXAFS spectrum is supported by Restricted Open-Shell Configuration Interaction (ROCIS) calculations. The fragmentation pathway of triply charged cystine ions was modeled by Molecular Dynamics (MD) simulations. We have deduced a possible pathway of fragmentation upon excitation and ionization of S 2p electrons. The disulfide bridge breaks for resonant excitation at lower photon energies but remains intact upon higher energy resonant excitation and upon ionization of S 2p. The larger fragments initially formed subsequently break into smaller fragments.
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| 4. |
- Rogmark, Cecilia, et al.
(författare)
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Post-discharge use of assistive devices following hemiarthroplasty : comparison of fracture patients with or without hip precautions
- 2019
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Ingår i: Disability and Rehabilitation: Assistive Technology. - : Informa UK Limited. - 1748-3107 .- 1748-3115. ; 14:8, s. 792-797
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To describe which types of assistive devices prescribed and actually used, either due to precautions or due to true functional reasons, after hip fracture-related hemiarthroplasty. Materials and methods: About 394 patients cluster-randomized 2010–2014 at a university hospital. Control group with standard postoperative precautions to reduce dislocations, mandatory assistive devices and knee brace for 6 weeks (in cognitively impaired) compared to non-precaution group with assistive devices only if needed. Postal questionnaire at 6 weeks and 3 months. Results: Both prescription and usage of reacher were higher in the precaution group. About 55% of patients with precautions was instructed to use stocking aids, 21% continued to do so. Significantly fewer without precautions, 11%, used it at 3 months. Raised toilet seat was used by ∼40% of all pre-fracture and was prescribed to 79% with precautions. It was unchanged at 42% in non-precaution group. Nevertheless, 64% in non-precaution group used a raised toilet both at 6 weeks and 3 months. The usage persisted around 70% in precaution group. Usage of raised chair/bed were similar, even if non-precaution patients was not prescribed such. In the precaution group, 102 were prescribed a knee brace, only 5 used it at 6 weeks. Conclusions: The use of assistive devices did not follow what was prescribed from the hospital, regardless of precautions or not. The use of higher furniture was similar regardless of precautions or not. Other devices were more common in the precaution group. The compliance of knee bracing was low, and bracing should not be standard-of-care.Implications for rehabilitation Hemiarthroplasty is the most common treatment of displaced femoral neck fracture in elderly. Dislocation occur in 2 to 10% of these patients, and traditionally patients have been instructed to be careful when moving their leg and to use a number of assistive devices, in order to reduce the dislocation risk. The evidence base for such precautions is weak and occupational therapy and assistive devices may be costly. The current study shows that prescriptions and instructions from occupational therapists in hospital is more or less not follow after dismissal. Assistive devices should be prescribed based on the hip fracture patient’s true functional needs, and not routinely or due to arthroplasty precautions.
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| 5. |
- Svensson, Pamela, et al.
(författare)
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Heavy element incorporation in nitroimidazole radiosensitizers : molecular-level insights into fragmentation dynamics
- 2024
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry. - 1463-9076 .- 1463-9084. ; 26:2, s. 770-779
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigates the photofragmentation behavior of iodine-enhanced nitroimidazole-based radiosensitizer model compounds in their protonated form using near-edge X-ray absorption mass spectrometry and quantum mechanical calculations. These molecules possess dual functionality: improved photoabsorption capabilities and the ability to generate species that are relevant to cancer sensitization upon photofragmentation. Four samples were investigated by scanning the generated fragments in the energy regions around C 1s, N 1s, O 1s, and I 3d-edges with a particular focus on NO2+ production. The experimental summed ion yield spectra are explained using the theoretical near-edge X-ray absorption fine structure spectrum based on density functional theory. Born-Oppenheimer-based molecular dynamics simulations were performed to investigate the fragmentation processes.
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