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- Ericsson, Rolf
(författare)
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A Comparative Study of Head Development in Mexican Axolotl and Australian Lungfish: Cell Migration, Cell Fate and Morphogenesis
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development of the vertebrate head is a complex process involving interactions between a multitude of cell types and tissues. This thesis describes the development of the cranial neural crest and of the visceral arch muscles in the head of two species. One, the Mexican axolotl (Ambystoma mexicanum), is a basal tetrapod, whereas the other, the Australian lungfish (Neoceratodus forsteri), belongs to the Dipnoi, the extant sister group of the Tetrapoda. The migration of neural crest cells, which form most of the bones and connective tissues in the head, and the morphogenesis of the jaw, was determined in the Mexican axolotl. It was shown that both the upper and lower jaws form from ventral condensations of neural crest cells in the mandibular arch. The dorsal condensation, earlier considered to give rise to the upper jaw, was shown to form the trabecula cranii.The normal spatio-temporal development of visceral arch muscles was investigated in both the Mexican axolotl and the Australian lungfish. In axolotl, the muscles tended to start forming almost simultaneously in all visceral arches at their future origins and extend towards their future insertions at the onset of muscle fibre formation. In lungfish, fibres formed simultaneously throughout most of each muscle anlage in the first and second visceral arch, but were delayed in the branchial arches. The anlagen were first observed at their future insertion, from which they developed towards future origins. To test the ability of neural crest cells to pattern the visceral arch muscles, migrating crest cells were extirpated from axolotl embryos, which resulted in a wide range of muscle malformations. In most cases, the muscles appeared in the right position but were small and extended in abnormal directions. This shows that neural crest cells are responsible not for the position of the muscles but for their correct anatomical pattern. Fate mapping showed that connective tissue surrounding myofibers is, at least partly, neural crest derived.In conclusion, the work presented in this thesis shows that although early development may map out the patterns of later development, the differences between axolotl and lungfish head development are not seen until during morphogenesis. Further investigation of morphogenesis is needed to explain the great variation of head morphology seen in vertebrates today.
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- Bülow, Margareta, et al.
(författare)
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Videoradiographic analysis of how carbonated thin liquids and thickened liquids affect the physiology of swallowing in subjects with aspiration on thin liquids.
- 2003
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Ingår i: Acta Radiologica. - : SAGE Publications. - 1600-0455 .- 0284-1851. ; 44:4, s. 366-372
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To analyze how carbonated thin liquids affected the physiology of swallowing in dysphagic patients. Material and Methods: 40 patients were analyzed; 36 were neurologically impaired. During a therapeutic videoradiographic swallowing examination the patients had to swallow liquids with the following consistencies three times: thin, thickened and carbonated. The liquids were given in doses of 3 x 5 ml. The swallows were analyzed regarding penetration/aspiration, pharyngeal transit time and pharyngeal retention. Results: Significant difference was found regarding penetration/aspiration when comparisons were made between thin liquid and carbonated thin liquid (p<0.0001). Carbonated liquid reduced the penetration to the airways. The comparison between thin liquid and thickened liquid (p<0.0001) showed significant less penetration with thickened liquids. Pharyngeal transit time was reduced both when comparing thin liquid with thin carbonated liquid (p<0.0001) and thickened liquid (p<0.0001). Pharyngeal retention was significantly reduced (p<0.0001) with carbonated thin liquid compared to thickened liquid. The comparison of thin liquids and carbonated thin liquids showed p = 0.0013, thin and thickened liquids p = 0.0097. Conclusions: Carbonated liquids reduced penetration/aspiration into the airways, reduced pharyngeal retention and pharyngeal transit time became shorter. Therefore, carbonated liquids are a valuable treatment option for patients with penetration/aspiration. Thickened liquids may still be an option for patients who cannot tolerate carbonated liquids and liquids with this consistency are safer than thin liquids.
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- Carlson, Jonas, et al.
(författare)
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Left Atrial Conduction along the Coronary Sinus during Ectopic Atrial Tachycardia and Atrial Fibrillation: A Study Using Correlation Function Analysis
- 2003
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Ingår i: Journal of Cardiovascular Electrophysiology. - : Wiley. - 1540-8167 .- 1045-3873. ; 14:10 Suppl, s. 148-153
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Tidskriftsartikel (refereegranskat)abstract
- ntroduction: Correlation function analysis was applied to endocardial electrograms to investigate conduction patterns along the coronary sinus (CS) during sinus rhythm (SR) and atrial tachycardias. Methods and Results: Eighteen recordings were obtained from 14 patients suffering from supraventricular tachycardias. Five atrial fibrillation(AF) recordings were compared to 10 SR recordings and 3 ectopic atrial tachycardia (EAT) recordings. The maximum correlation coefficient was used to assess similarity between signals, i.e., if they originate from the samewavefront. The cumulative time delay, calculated as pairwise summation of interelectrode time delays was used as an indicator of activation sequence along CS. Method validation using SR showed right to left conduction with high correlations in 8 of 10 recordings indicating one single wavefront. EAT recordings showed consistent left to right conduction with left atrial foci and right to left with right atrial focus and lower correlations than SR. All 5 AFrecordings showed predominantly left to right conduction direction, also with correlations lower than SR.Conclusion: 1) Correlation function analysis can be used to assess agreement between signals and direction of activation spread. 2) Due to the position of CS, the results can be used to derive mechanisms of interatrial conduction. 3) Consistency in electrical activity propagation along CS iscommon in AF.
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- Olsson, Tomas, et al.
(författare)
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Visual Position Tracking using Dual Quaternions with Hand-Eye Motion Constraints
- 2003
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Ingår i: Proceedings. ICRA '03.. - 2152-4092 .- 1050-4729. - 0780377362 ; 3, s. 3491-3496
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Konferensbidrag (refereegranskat)abstract
- In this paper a method for contour-based rigid body tracking with simultaneouscamera calibration is developed. The method works for a singleeye-in-hand camera with unknown hand-eye transformation,viewing a stationary object with unknown position. The method usesdual quaternions to express the relationship between the camera- andend-effector screws. It is shown how using the measured motion of therobot end-effector can improve the accuracy of theestimation, even if the relative position and orientation between sensorand actuator is completely unknown.The method is evaluated in simulations on images from a real-time 3D renderingsystem. The system is shown to be able to track the pose of rigid objects and changes in intrinsic camera parameters, using only rough initial values for the parameters. The method is finally validated in anexperiment using real images from a camera mounted on an industrial robot.
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- Tunestål, Per, et al.
(författare)
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Closed-Loop Combustion Control of HCCI Engines
- 2003
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Ingår i: Nonlinear and Hybrid Systems in Automotive Control. ; , s. 321-334
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The HCCI engine, with its excellent potential for high efficiency and low NOx emissions, is investigated from a control perspective. Combustion timing, i.e., where in the thermodynamic cycle combustion takes place, is identified as the most challenging problem with HCCI engine control. A number of different means for controlling combustion timing are suggested, and results using a dual-fuel solution are presented. This solution uses two fuels with different ignition characteristics to control the time of autoignition. Cylinder pressure measurement is suggested for feedback of combustion timing. A simple net-heat release algorithm is applied to the measurements, and the crank angle of 50% burnt is extracted. Open-loop instability is detected in some high-load regions of the operating range. This phenomenon is explained by positive feedback between the cylinder wall heating and ignition timing processes. Closed-loop performance is hampered by time delays and model uncertainties. This problem is particularly pronounced at operating points that are open-loop unstable.
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