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- Fredriksson, Ingemar, 1980-, et al.
(författare)
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Microcirculatory changes in type 2 diabetes assessed with velocity resolved quantitative laser Doppler flowmetry
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The response to local heating (44oC for 20 min) was evaluated in 28 type 2 diabetes patients (DM) and 29 non-diabetes controls (ND). Microcirculatory perfusion was assessed using conventional and quantitative Laser Doppler flowmetry (cLDF and qLDF), respectively. The qLDF estimates perfusion in a physiological relevant unit (g RBC / 100 g tissue × mm/s) in a fixed output volume, separated into three velocity regions, v < 1 mm/s, 1 - 10 mm/s, and v > 10 mm/s. Perfusion in cLDF is given in arbitrary units with unknown velocity distribution and measurement volume. A significantly lower response in DM than in ND was found after heat provocation both for the initial peak and the plateau response, while no significant differences were found at baseline. The qLDF showed increased perfusion for the velocity regions 1-10 mm/s and above 10 mm/s, while no significant increase was found for v < 1 mm/s. In conclusion, we found a lowered LDF response to local heating in DM. The new qLDF method showed that the increased blood flow occurs in vessels with a velocity above 1 mm/s. Baseline qLDF-data indicated that a redistribution of flow to higher velocity regions was associated with longer DM duration and for DM a negative correlation between perfusion and BMI.
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- Holmgren, Helene, 1981, et al.
(författare)
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Influence of Film Dimensions on Film Droplet Formation
- 2011
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Background: Aerosol particles may be generated from rupturing liquid films through a droplet formation mechanism. The present work was undertaken with the aim to throw some light on the influence of film dimensions on droplet formation with possible consequences for exhaled breath aerosol formation. Methods: The film droplet formation process was mimicked by using a purpose-built device, where fluid films were spanned across holes of known diameters. As the films burst, droplets were formed and the number and size distributions of the resulting droplets were determined. Results: No general relation could be found between hole diameter and the number of droplets generated per unit surface area of fluid film. Averaged over all film sizes, a higher surface tension yielded higher concentrations of droplets. Surface tension did not influence the resulting droplet diameter, but it was found that smaller films generated smaller droplets. Conclusions: This study shows that small fluid films generate droplets as efficiently as large films and that droplets may well be generated from films with diameters below 1 mm. This has implications for the formation of film droplets from reopening of closed airways since human terminal bronchioles are of similar dimensions. Thus, the results provide support for the earlier proposed mechanism where reopening of closed airways is one origin of exhaled particles.
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- Jedenmalm, Anneli, et al.
(författare)
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Effect of γ-irradiation sterilization in nitrogen on oxidation of hip-simulated UHMWPE cups
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A hip simulator study with roughened heads revealed unexpected high wear rates for the γ-irradiated UHMWPE cups (sterilization performed in nitrogen) and also higher fluid absorbtion than that of the non-sterilized cups. Infrared spectroscopy and high-resolution scanning of samples stained with HCl and SO2 showed that the outer parts of cross-sections of the sterilized cups were oxidized after the wear testing. The non-sterilized cups showed essentially no polymer oxidation with only minor surface oxidation due to roughened head. The higher wear rate and the more extensive fluid absorption of the sterilized cups is thus attributed to oxidation of the polymer; the latter presumably being facilitated by the presence of long-living radicals generated during γ-irradiation sterilization.
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- Jonsson, Ulf G, et al.
(författare)
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Using Standing Lamb waves and the Finite Element Method to Detect Hard Inclusions in Silicone Rubber Disks
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The presence of an inclusion in a cylindrical silicone rubber disk is determined using FEM, standing Lamb waves, and an algorithm using multiple frequency footprints. Radial elastic waves are emitted into the disk by a cylindrical piezoelectric sensor placed in the center of the disk. The visco-elastic properties of the silicone rubber disk is modeled by a fractional derivative model and the hyperelastic effect at the radial resonance frequency was compensated for. Using the finite element model, the Lamb wave transition frequencies in the impedance frequency response of the sensor was calculated for a specified position of the inclusion. The set of frequencies was named the footprint for that position. The position of the inclusion was varied between 0.05 to 0.95, with a step of 0.01, of the radial length of the silicone rubber disk. For each position, a footprint was calculated. The footprints,s, with corresponding positions, were stored in a database. A positioning algorithm was developed that could match an unknown footprint to a footprint in the database. A self-test of the algorithm showed that the correct position was found for 94% of the tested positions. The results of the positioning algorithm was that the presence of the inclusions were detected, and that the positions of the inclusions at 0.38 and 0.63 were estimated by the positioning algorithm as: 0.45 and 0.74, with relative errors +18% and +17% respectively. The positions are given as the ratio of the radius of the inclusion to the silicone rubber disk radius.
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- Larsson, Matilda, 1981-
(författare)
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The rotation axis of the left ventricle - A new concept derived from ultrasound data in healthy individuals
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Annan publikation (populärvet., debatt m.m.)abstract
- Different modalities have been used to describe the circumferential motion of the left ventricle (LV) and studies have indicated LV twist to be an additional integral component in LV function. So far, only amplitudes of rotation have been reported, whereas the rotation pattern of the LV has not been fully described. However, data from a previous study on regional rotation have indicated that the axis around which the LV rotates, is not congruent to the longitudinal axis of the LV. The aim of the present study was to develop an ultrasound-based method to calculate the rotation axis of the LV in a three-dimensional aspect throughout the cardiac cycle and to apply it in a group of healthy individuals. An algorithm for calculation of rotation axes at the basal, mid-, apical and transitional levels of the LV was developed. By constructing a simplified model of the LV, based on rotation amplitudes measured at the basal, mid- and apical levels, rotation planes with similar values of rotation could be calculated at each level. The transition plane was defined as where the rotation values shifted from positive to negative. An overview of the rotation pattern was achieved by displaying data on deflection (angle between the rotation axis and the longitudinal axis of the LV) and direction (defined as the angle in a short-axis view of the LV with zero degrees at the lateral wall and increasing angles counterclockwise) of the rotation axes throughout the cardiac cycle. The deflection differed significantly from zero in all tested time points, i.e. the rotation axis was not congruent to the longitudinal axis of the LV. Rayleigh’s test for uniformity demonstrated a significant mean direction for each of the axes for the majority of the tested time points. Thus, the axis of rotation at different levels of the LV displayed a physiological pattern, where also stability of rotation could be assessed. Furthermore, the angle and level of the transition plane could be described over time. This new way of assessing rotational function provides further insight into the complexity of LV mechanics. The method has acceptable reproducibility but the potential clinical use of this method needs to be validated in further studies.
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