| 1. |
- Vedung, Fredrik, et al.
(författare)
-
Chronic cerebral blood flow alterations in traumatic brain injury and sports-related concussions
- 2022
-
Ingår i: Brain Injury. - : Taylor & Francis Group. - 0269-9052 .- 1362-301X.
-
Tidskriftsartikel (refereegranskat)abstract
- Primary ObjectiveTraumatic brain injury (TBI) and sports-related concussion (SRC) may result in chronic functional and neuroanatomical changes. We tested the hypothesis that neuroimaging findings (cerebral blood flow (CBF), cortical thickness, and 1H-magnetic resonance (MR) spectroscopy (MRS)) were associated to cognitive function, TBI severity, and sex.Research DesignEleven controls, 12 athletes symptomatic following ≥3SRCs and 6 patients with moderate-severe TBI underwent MR scanning for evaluation of cortical thickness, brain metabolites (MRS), and CBF using pseudo-continuous arterial spin labeling (ASL). Cognitive screening was performed using the RBANS cognitive test battery.Main Outcomes and ResultsRBANS-index was impaired in both injury groups and correlated with the injury severity, although not with any neuroimaging parameter. Cortical thickness correlated with injury severity (p = 0.02), while neuronal density, using the MRS marker ((NAA+NAAG)/Cr, did not. On multivariate analysis, injury severity (p = 0.0003) and sex (p = 0.002) were associated with CBF. Patients with TBI had decreased gray (p = 0.02) and white matter (p = 0.02) CBF compared to controls. CBF was significantly lower in total gray, white matter and in 16 of the 20 gray matter brain regions in female but not male athletes when compared to female and male controls, respectively.ConclusionsInjury severity correlated with CBF, cognitive function, and cortical thickness. CBF also correlated with sex and was reduced in female, not male, athletes. Chronic CBF changes may contribute to the persistent injury mechanisms in TBI and rSRC.
|
|
| 2. |
- Andersson, Sara, et al.
(författare)
-
Damage monitoring of ship FRP during exposure to explosion impacts
- 2011
-
Konferensbidrag (refereegranskat)abstract
- Fiber Reinforced Plastics (FRP) has been used by Kockums' shipyard in the manufacturing of ships over 35 years, during which time is has been proven to be durable and practical. The light weight makes it a more and more attractive material as energy and material expenditure decreases are required. A special application is the Composite Superstructure Concept [1] where composite materials are added on top of a steel hull, which decreases the weight and running costs considerably, and makes it possible to even add extra levels while keeping the same center of gravity. If efficient condition monitoring systems can keep track of emerging damages of the structure, the weight may be even more reduced and the interval between maintenance inspections may be prolonged. As important steps in this process, a ship mock-up section was subjected to increased levels of explosive underwater impacts, and the damage progression in the hull was monitored by a nonlinear acoustic technique.
|
|
| 3. |
- Hedberg, Claes, et al.
(författare)
-
Non-contact nonlinear acoustic damage localization in plates. Part 1 : Resonance of air between plates
- 2007
-
Ingår i: Acta Acoustica united with Acustica. - : S HIRZEL VERLAG. - 1610-1928 .- 1861-9959. ; 93:1, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- This is the first of three articles that deals with the goal of using non-contact nonlinear acoustic methods for the damage localization in plates. In this first part, the resonant air gap wave field between one active and one passive reflecting plate was investigated experimentally. Of particular interest is the wave field amplitude strength, and its distribution on the passive surface. The wave amplitude may be increased by choosing one plate to be concave, overcoming the nonlinear damping taking place for two flat plates. Applications are connected with an increased wave field having advantages for processes taking place under open conditions and for a non-contact transducers' efficiency of transferring energy into an object. A double resonance gives highest air pressure, while a triple provides most energy in the passive object. By choosing the gap distance, frequency and transducer width, the appearing resonant wave will have a considerably larger amplitude at the object surface. The work through the interface from air to object is investigated and the wave field in a resonant air-plate system is shown.
|
|
| 4. |
- Hedberg, Claes, et al.
(författare)
-
Non-contact nonlinear ultrasound scan of a CFRP plate with manufactured damages
- 2013
-
Konferensbidrag (refereegranskat)abstract
- A Carbon Fibre Reinforced Plastic plate was manufactured to have internal damages of different types. A nonlinear ultrasound technique was used to scan the plate. Non-contact transmitters of own design were used as transducer, and a contact sensor was used to measure the wave in the composite. Scanning was made perpendicularly with the sensor being on the same side as the transducer. The technique can be adapted in accuracy and speed.
|
|
| 5. |
- Hedberg, Claes, et al.
(författare)
-
Ultrasonic monitoring of a fiber reinforced plastic : steel composite beam during fatigue
- 2012
-
Ingår i: Proceedings of the 6th European Workshop - Structural Health Monitoring 2012, EWSHM 2012. - Dresden : German Society for Nondestructive Testing. ; , s. 1254-1260
-
Konferensbidrag (refereegranskat)abstract
- The use of composite superstructures on current or newly built steel hulls is a recently emerged technology. The economic estimations predict that the extra costs for putting composite superstructures, with the present safety margins, on steel ships will be paid back in only 2-3 years. This also makes the ships having smaller ecological footprints with less fuel consumption and CO2 emissions. In this stage of development it is needed to ensure the durability of the joints between the steel and glass fiber reinforced plastic. The first step is that the joints must first be proven to withstand fatigue. In this test a 4-meter beam, which represents the joint, were investigated for fatigue progression by a four-point-bending fatigue test. In order to show that ultrasonic material monitoring techniques can be used to monitor the damage progression, the beam was measured during the tests until failure. The test was successful both in showing that the joint could withstand high levels of mechanical exposure, and in that the ultrasonic techniques accompanied the damage progression which means that they may be used on vessels during operation
|
|
