| 1. |
- Johansson, Kristin, 1983-
(författare)
-
Oxygen-reducing enzymes in coatings and films for active packaging
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxygen scavengers are used in active packages to protect the food against deteriorative oxidation processes. The aim of this work was to investigate the possibilities to produce oxygen-scavenging packaging materials based on oxygen-reducing enzymes. The enzymes were incorporated into a dispersion coating formulation applied onto a food-packaging board using conventional laboratory coating techniques.Various enzymes were used: a glucose oxidase, an oxalate oxidase and three laccases originating from different organisms. All of the enzymes were successfully incorporated into a coating layer and could be reactivated after drying. For at least two of the enzymes, re-activation was possible not only by using liquid water but also by using water vapour. Re-activation of the glucose oxidase and a laccase required relative humidities of greater than 75% and greater than 92%, respectively.Catalytic reduction of oxygen gas by glucose oxidase was promoted by creating an open structure through addition of clay to the coating at a level above the critical pigment volume concentration. Migration of the enzyme and the substrate was reduced by adding an extrusion-coated liner of polypropylene on top of the coating.For the laccase-catalysed reduction of oxygen it was possible to use lignin derivatives as substrates for the enzymatic reaction. The laccase-catalysed reaction created a polymeric network by cross-linking of lignin-based entities, which resulted in increased stiffness and increased water-resistance of biopolymer films. The laccases were also investigated with regard to their potential to function as oxygen scavengers at low temperatures. At 7°C all three laccases retained more than 20% of the activity they had at room temperature (25°C), which suggests that the system is also useful for packaging of refrigerated food.
|
|
| 2. |
|
|
| 3. |
- Barros, Gustavo Gil, 1976-
(författare)
-
Influence of Substrate Topography on Ink Distribution in Flexography
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The printability of paper in flexography is largely dependent on the topographical characteristics of the substrate. Topography imaging instruments make it possible to obtain three-dimensional scans of paper surfaces that can be further used to calculate valuable quality parameters. The primary aim of the work described in this thesis has been to identify and isolate structural properties of the paper surface which significantly influence the ink distribution during printing and limit the subsequently attainable print quality.OptiTopo is an optical imaging technique which provides precise and fast topographic scans of both printed and unprinted paper surfaces. The potential and limitations of the technique have been evaluated. The optical requirements on the substrate for an accurate and precise topographic scan were determined. Detail-rendering was substantially improved using a custom-designed restoring filter, and a new enhanced spatial resolution range was established. A combination of further algorithm improvements made it possible also to obtain reflectance-factor-calibrated intensity images of scanned printed surfaces.Serious deficiencies affecting the quality of flexographic prints may appear in the form of local unprinted areas (UCA) in a full-tone print, generally caused by incomplete ink transfer. An algorithm detecting and quantifying local uncovered area was developed, tested and successfully integrated with the OptiTopo instrument. A UCA occurrence frequency distribution, indicating the percentage of the uncovered area at a certain topographical elevation, was calculated for different prints. The topographic characteristics of the uncovered areas clearly indicate that surface depressions are the primary cause of uncovered areas in flexographic printing.Four different predictive models based on topography thresholding were proposed and tested using two independent quality judgement criteria. These quality indices took into account both the amount and location of the predictions. A deeper understanding of the topographical features governing UCA occurrence was established with a proposed ink bridging effect. The total risk of non-ink-covered areas in flexography printing due to topographical features was estimated.The overall influence of paper topography on the flexography printability of full-tone areas was studied and its importance for the ink distribution assessed. The impacts of printing plate hardness, printing pressure, anilox cylinder volume and substrate roughness were quantified. Two typical flexography patterns were identified and their origin discussed: sub-millimetre elongated structures and millimetre-scale blotches.
|
|
| 4. |
- Jans, Jenny, 1984-
(författare)
-
Causes and Consequences of Early-life Conditions : Alcohol, Pollution and Parental Leave Policies
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Essay I: This paper studies the effect of air pollution on infant health in Sweden. Combining register panel data on birth outcomes and family characteristics with pollution data, I estimate the effect of particulate matter (PM10) on several birth outcomes that previously have been shown to be predictive of future outcomes. The results suggest that pollution adversely affects infant health (birth weight and gestational length). Moreover, quantile estimates suggests that the effects are larger in the lower tail of the health distribution. The effect is stronger both among children from low income households and among children born to mothers who smoke. I also find suggestive evidence of non-linearities in the relationship between PM10 and health at birth.
|
|
| 5. |
- Johansson, Ann-Christin
(författare)
-
Psychosocial factors in patients with lumbar disc herniation : enhancing postoperative outcome by the identifiction of predictive factors and optimised physiotherapy
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Psychosocial factors have been advanced as an explanation for the development of chronic disability in 20 to 30% of patients treated by lumbar disc surgery. Aims: The overall aim of this thesis was to study the role of psychosocial factors in patients undergoing first-time lumbar disc surgery in relation to the outcome of both surgery and subsequent physiotherapy. Methods: Sixty-nine patients with lumbar disc herniation undergoing first-time disc surgery participated in the studies; in addition, Study I included 162 knee patients for comparison. Psychosocial factors were assessed preoperatively, as was the activation of the physiological stress response system. Pain, disabil-ity and quality of life were assessed before, and 3 and 12 months after surgery. Coping and kinesiophobia were analysed before and one year after surgery. The results of two different postoperative training programmes were compared. Results: There were no differences between disc and knee patients regarding the presence of psychosocial stress factors preoperatively (Study I). Disc patients with low diurnal cortisol variability had lower physical function, perceived fewer possibilities to influence their pain and were more prone to catastrophise than patients with high diurnal cortisol variability (Study II). The results of clinic-based physiotherapy and home training did not differ regarding postoperative disability and pain 3 months after surgery. The home-based group had less pain and higher quality of life in comparison to the clinic-based group 12 months after surgery (Study III). Patients’ expectations of returning to work could best predict pain, disability, quality of life and sick leave one year after surgery (Study IV). Psychosocial factors were only weakly asso-ciated to pain, disability, quality of life and sick leave preoperatively. However, these associations were stronger in patients with residual pain one year after surgery. Conclusion: Psychosocial factors and, in particular, patients’ expectations regarding outcome are associated with the results of lumbar disc surgery. Assessing psychosocial factors preoperatively and developing an active home training programme after surgery could create options leading to better results for these patients.
|
|
| 6. |
- Johansson, Anders J
(författare)
-
Wireless Communication with Medical Implants: Antennas and Propagation
- 2004
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the increased sophistication of medical implants, there is a growing need for flexible high-speed communication with the implant from outside the body. Today the communication is done by an inductive link between the implant and an external coil at a low carrier frequency. Extended range and communication speed are possible to achieve by increasing the carrier frequency and the bandwidth. One frequency band that is available for this application is the newly standardized 400 MHz MICS band, which has the benefit of being reserved mainly for medical and metrological applications. In addition, the 2.45 GHz ISM band is a possibility, but has the drawback of being heavily used by other applications, such as wireless computer networks and microwave ovens. In order to assess the usability of wireless communication with medical implants, we have investigated the design of implantable antennas to be used in the body. Both theoretical limits and practical designs of the antennas are described. The SAR levels of the implanted antennas have been calculated and have been found to be at a safe level. We have investigated the wave-propagation from the implanted antenna to the outside, and its dependence on the position of the patient’s limbs and the size of the body. Full wave 3D-simulations of the wave propagation are feasible, as the radio link between the patient and a base station placed in the same room is very short in terms of wavelengths in the MICS band. We have simulated the wave propagation in a furnished room and compared the results with measurements of the same room. The results from these investigations are evaluated in terms of their impact on the link budget for a prototype MICS system. From these calculations conclusions on the necessary complexity of the transceivers are drawn, such as the need for both spatial and polarization diversity to fully exploit the potential of the communication link.
|
|
| 7. |
- Johansson, Bengt J O, 1948
(författare)
-
Betong i arkitekturen. Gestaltning och teknik 1930-1980
- 2008
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Bengt J O Johansson: Betong i arkitekturen. Gestaltning och teknik 1930–1980 (Concrete in Architecture. Design and Technology 1930–1980). Göteborg 2008.Written in Swedish with an English summary.This is a study of the interaction between design and technology for buildings of concrete construction during 1930-1980. Its aim is to describe the design and constructional development during the different stages of style change throughout this period, and how design and technology have influenced each other. Knowledge about building technology utilising concrete is essential for understanding the building heritage of our own era.The study encompasses architecture and construction technology. The sources are literature and drawings, and the buildings themselves.The study begins with an account of the development of concrete building technology during the period in question. Construction technology provides the basis for the analysis of the interaction with architecture. This interaction is described in three thematically sectioned chapters and summarised and analysed in a concluding chapter. These thematic chapters deal with concrete as ’the material for modernism’, as ‘the material for design’ and as ‘the material for rationalism’.Concrete construction was at the beginning of the 1930s an ideal in the creation of functionalist (modernistic) architecture, even if the structures were initially mostly of traditional character. During this decennium, however, concrete became the most commonly used material for construction in buildings.From the 1950s onwards, on-site concrete constructions were utilised in the creation of buildings of character. The textured surface of the concrete, often derived by carefully shaped casts or through finishing processes made a vital contribution to the design. Concrete formed load-bearing elements and constructions gave design to interiors, exte-riors, and even complete volumes. Architects adopted concrete construction technology and at the same time freed themselves from traditional architecture with historical roots. This resulted in painstakingly designed concrete buildings.Parallel with this, from the 1960s onwards, industrialised construction with precast concrete modular sections for entire building structures and façades were developed. Here the construction process and prefabrication technology became design-oriented motives, often finding expression through their large-scale, repetition, and duplication of identical modular units in the individual building and the repetition of identical buildings. The concrete surfaces of the façades’ sectional units were produced rationally; they formed and accentuated this industrialised construction.
|
|
| 8. |
- Johansson, Daniel, 1980-
(författare)
-
Convergence in mixed reality-virtuality environments : facilitating natural user behavior
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis addresses the subject of converging real and virtual environments to a combined entity that can facilitate physiologically complying interfaces for the purpose of training. Based on the mobility and physiological demands of dismounted soldiers, the base assumption is that greater immersion means better learning and potentially higher training transfer. As the user can interface with the system in a natural way, more focus and energy can be used for training rather than for control itself. Identified requirements on a simulator relating to physical and psychological user aspects are support for unobtrusive and wireless use, high field of view, high performance tracking, use of authentic tools, ability to see other trainees, unrestricted movement and physical feedback. Using only commercially available systems would be prohibitively expensive whilst not providing a solution that would be fully optimized for the target group for this simulator. For this reason, most of the systems that compose the simulator are custom made to facilitate physiological human aspects as well as to bring down costs. With the use of chroma keying, a cylindrical simulator room and parallax corrected high field of view video see-though head mounted displays, the real and virtual reality are mixed. This facilitates use of real tool as well as layering and manipulation of real and virtual objects. Furthermore, a novel omnidirectional floor and thereto interface scheme is developed to allow limitless physical walking to be used for virtual translation. A physically confined real space is thereby transformed into an infinite converged environment. The omnidirectional floor regulation algorithm can also provide physical feedback through adjustment of the velocity in order to synchronize virtual obstacles with the surrounding simulator walls. As an alternative simulator target use, an omnidirectional robotic platform has been developed that can match the user movements. This can be utilized to increase situation awareness in telepresence applications.
|
|
| 9. |
|
|
| 10. |
- Johansson, Mats J., 1958-
(författare)
-
Gas Exchange in the Normal Lung : Experimental studies on the effects of positive end-expiratory pressure and body position
- 2014
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- BACKGROUND: The principal function of the lung is gas exchange requiring adequate ventilation and perfusion at the level of the alveoli. The efficiency of gas exchange is depending on the distributions of regional ventilation (V) and pulmonary blood flow (Q) and their correlation.AIMS: To validate a high-resolution method to quantify regional V and to investigate the combined effect of positive end-expiratory pressure (PEEP) and body position on distributions of regional V and Q in the normal lung with mechanical ventilation. To assess the matching of V and Q by calculating ventilation-perfusion ratio (V/Q) heterogeneity, determining the spatial distribution of V/Q and to investigate the role of nitric oxide (NO) in regional V/Q matching.METHODS: Anesthetized mechanically ventilated sheep were studied in prone or supine position with different levels of PEEP (0, 10 and 20 cmH2O). Measurements of regional V were done by determining the deposition of a wet aerosol of fluorescent microspheres (FMS) with a median mass aerodynamic diameter of 1.1 μm, and validated against Technegas. Radioactive microspheres, 15 μm in diameter, were used for determining regional Q. Nitric oxide synthase (NOS) was inhibited with Nω-nitro-L-arginine methyl ester (L-NAME) to evaluate the role of NO on regional V/Q matching. The right lung was dried at total lung capacity and diced in approx. 1000 regions tracking the spatial location of each region.RESULTS: The deposition of FMS mirrored regional deposition of Technegas and thus regional ventilation well. In prone, with PEEP, only a small dorsal redistribution of V but not of Q was observed. The vertical Q gradient was abolished with PEEP in prone position in conflict with the classical zonal model. In supine position both V and Q were distributed with a unimodal gradient and PEEP displaced the mode further dorsally. V/Q heterogeneity was greater in supine than in prone position with and without PEEP. Furthermore, PEEP generated regions with high V/Q in supine but not in prone position. Inhibition of NOS did not change the V/Q distribution in prone position.CONCLUSION: There were marked differences in redistribution of regional ventilation and regional pulmonary blood flow between prone and supine position when PEEP was applied. NO was not an active mechanism for V/Q matching in normal sheep lungs.
|
|
