| 1. |
- Abrahamsson, Lars, et al.
(författare)
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High-voltage DC-feeder solution for electric railways
- 2012
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Ingår i: IET Power Electronics. - : Institution of Engineering and Technology. - 1755-4535 .- 1755-4543. ; 5:9, s. 1776-1784
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Tidskriftsartikel (refereegranskat)abstract
- For AC railway power supply systems with a different frequency than the public grid, high-voltage AC transmission lines are common, connected to the catenary by transformers. This study suggests an alternative design based on an high-voltage DC (HVDC)-feeder, which is connected to the catenary by converters. Such an HVDC line would also be appropriate for DC-fed railways and AC-fed railways working at a public-grid frequency. The converter stations between the public grid and the HVDCfeeder can be sparsely distributed, not denser than on 100 km distances, whereas the converters connecting the HVDC-feeder to the catenary are distributed denser. Their ratings can be lower than present-day substation transformers or converters, since the power flows can be fully controlled. Despite a relatively low-power rating, the proposed converters can be highly efficient because of the use of medium frequency technology. The proposed feeding system results in lower material usage, lower losses and higher controllability compared with the present solutions. Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared with conventional systems, especially for cases with weak feeding, and when there are substantial amounts of regeneration from the trains.
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| 2. |
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| 3. |
- Adamsson, I, et al.
(författare)
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Microbial ecology and treatment of Helicobacter pylori infections : Review
- 2000
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Ingår i: Journal of chemotherapy. - 1120-009X .- 1973-9478. ; 12:1, s. 5-16
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Forskningsöversikt (refereegranskat)abstract
- The aims of the present study were to investigate the ecological disturbances caused by four different anti-H. pylori regimens, to compare different methods for diagnosing H. pylori, and to study the genetic variability of H. pylori. The patients included in the study were all treated at the Center of Gastroenterology, Huddinge University Hospital, Karolinska Institute. All patients were H. pylori-positive before entering the study, confirmed by rapid urease test, histology, culture and urea breath test or PCR. Treatment regimens included in the study were omeprazole alone (OP), in combination with amoxicillin (OA), in combination with amoxicillin and metronidazole (OAM) and in combination with clarithromycin and metronidazole (OCM). Samples from the mouth (saliva and dental plaque), stomach (biopsies from the gastric mucosa in the corpus and in the antrum) and the intestine (feces) were collected before, during and after treatment. The oral microflora was challenged by the three treatment regimens including antimicrobial agents, with the emergence of resistant streptococci and staphylococci in the OCM group. Bacterial strains in the gastric mucosa increased in numbers during treatment in all treatment groups, probably due to the pH rise, which provides a better environment for the commensal microflora. This overgrowth was especially pronounced during treatment with omeprazole alone (OP), possibly due to the fact that a concomitant suppression exerted by the antimicrobial agents occurred in the other treatment groups. H. pylori was, on the other hand, suppressed during treatment in all treatment groups, possibly due to a direct effect of omeprazole and to the colonization resistance expressed by the normal microflora, An emergence of resistant commensal strains in the gastric mucosa was seen in the OCM and the OAM groups. The intestinal microflora was most altered in the OAM and the OCM groups, with persistent disturbances in the OCM group 4 weeks after treatment. The frequency of resistant Enterococcus spp, (OCM), Enterobacteriaceae spp, (OA and OAM) and Bacteroides spp, (OCM) was increased during and after treatment. Different detection methods for H. pylori were compared and PCR was shown to have higher sensitivity than other routine diagnostic tests. The patients in the present study seemed to be colonized with a single strain of H. pylori. Treatment failures in patients treated with OAM were caused by recrudescence. These four patients with relapsing H. pylori infection, were shown to be reinfected with the original H. pylori strain, indicating that H. pylori escapes treatment by a thus far unknown mechanism.
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| 6. |
- Ahlgren, Inger, et al.
(författare)
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Det svenska teckenspråket
- 2006
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Ingår i: Teckenspråk och teckenspråkiga. Kunskaps och forskningsöpversikt. - 9138225468 ; , s. 11-70
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 7. |
- Ahlgren, Inger
(författare)
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Utbildningsplaner och reformimplementering : Sjuksköterskeutbildningen i fokus
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study describes the course of events within the area of health care with regard to two educational reforms in Sweden: the 1982 reform of certain middle length health care education called the Health Care 77 reform and the 1993 University and College reform. As a result of the first of these reforms, the nursing education was transformed from an education on the secondary school level to a university college level.The present study which has its underpinnings within the implementation process has twoaims: first to clarify the governmental intentions and to illustrate how these intentions wereinterpreted and formulated by those in charge of executing the reforms and secondly toinvestigate to what degree other factors than those directly connected to the actual reformshave influenced the content and form of the operative activities.The frame of reference describes the problems of political governing of education as twofold: the process of making political decisions and the process of executing those decisions.The reality where the goals are formulated and reality where goals are realized are governedby different contingencies, which may be difficult to bridge between. In the present study, thepolitical governing of a reform is seen in a curriculum theoretical perspective and theexecution of the reform is seen in an organization theoretical perspective.The empirical material in this study entails primarily government and local documentssupplemented by interview studies along with studies of correspondence studies with thoseinvolved in the units of interest.There are two main results of this study. The first result was that the formal politicalgoverning of an education has a certain impact but that the informal execution of a reformwill be dependent upon the values and culture of those in the local organization. The secondresult showed that the implementation process entails two phases: a transformation phasewhere government directives are reformulated into local documents and an implementationphase where the local documents are executed in an activity. Commonly, researchers includethe transformation phase within the implementation process but the results of this studysuggest that it may be of greater value to view the transformation phase as phenomena, whichcan be both defined and studied on its own.
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| 8. |
- Akterin, Susanne
(författare)
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From cholesterol to oxidative stress in Alzheimer's disease : a wide perspective on a multifactorial disease
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epidemiological studies have provided evidence that high cholesterol levels in midlife and lack of antioxidants could render people more susceptible to develop AD. The aim of this thesis project was to get a more profound view of how cholesterol and oxidative stress could modify the development of Alzheimer s disease (AD) on the molecular level, by studying mechanisms of signal transduction. In Paper I we studied the effects of ApoE deficiency in combination with high fat/high cholesterol intake on mouse brain, and found that these two factors have synergistic effect on tau phosphorylation, causing hyperphosphorylation. In Paper II we used microarray to examine how the expression of individual genes in brain is affected by long-term high fat/high cholesterol diet. We found changes in a limited number of genes, of which several have previously been linked to neurodegenerative processes. We focused our investigation on activityregulated cytoskeletal-associated protein (Arc), that is important for synaptic plasticity and memory. Arc expression was decreased in brains from mice that received a high-fat/high cholesterol diet, as well as in Alzheimer brain. It is likely that this effect was induced by 27-hydroxycholesterol, a cholesterol metabolite that is able to cross the blood-brain barrier. We went on to study how oxidative stress affects the brain and in Paper III we found that glutaredoxin-1 (Grx1) and thioredoxin-1 (Trx1) are first in line to protect cells against oxidative stress caused by Abeta. Levels of Grx1 and Trx1 were found to be affected in AD brain and this de-regulation could result in activation of apoptosis signal-regulating kinase (ASK)1, with important consequences for Abeta-induced cell death. The final study concerned thioredoxin-80, a cleavage product of Trx1, earlier found to be produced when Trx1 is oxidized. In Paper IV we found that Trx80 is present in brain, mainly in neurons, that it is produced by cleavage of Trx1, by ADAM10/17 (alpha-secretase), and that the levels were decreased in AD brain. Suggested functions of Trx80 in brain are to protect against Abeta-induced cell death, possibly by regulating apoptosis, by degradation of ASK1. In conclusion, AD is a heterogeneous disease, affecting many different cellular processes and signaling pathways, a notion that is further supported by the results presented in this thesis. Since we do not yet know the underlying mechanisms for the disease development the study of risk factors is an alternative way of addressing this problem. The field of risk factors for AD has lately developed rapidly, but more effort is needed to understand the underlying mechanisms for the risk modifying effects. Further investigation in this area is needed, and will provide knowledge on how one should live to prevent the development of AD as well as suggest new targets for drug therapy.
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| 9. |
- Alawode, Abiodun, et al.
(författare)
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Properties and characteristics of novel formaldehyde-free wood adhesives prepared from Irvingia gabonensis and Irvingia wombolu seed kernel extracts
- 2019
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Ingår i: International Journal of Adhesion and Adhesives. - : Elsevier. - 0143-7496 .- 1879-0127. ; 95
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Tidskriftsartikel (refereegranskat)abstract
- There is renewed interest in the domestication of Irvingia tree species due to the potential use of various parts of the tree as raw materials for a wide range of applications such as biodiesel production, cosmetics, perfumes, soap, weight-loss supplement etc. The current study investigates the properties of extracts from the seed kernels of two Irvingia species – Irvingia gabonensis (IG) and Irvingia wombolu (IW) as natural wood adhesives. Three extraction methods using various solvent/solute media were compared in terms of yield, composition and mechanical properties. Statistically, the analysis revealed significant differences between the different extraction methods. The adhesion properties of the extracts were tested on wood veneers according to the American Society for Testing and Materials standard (ASTM D – 906-64). The shear strength of the extracts ranged from 0.55 to 1.5 MPa and 0.86 to 1.7 MPa for IG and IW, respectively. The initial decomposition temperature of all Irvingia Kernel extract ranges from 138.3 – 149.11 oC for IG and 129.5 – 145.3 oC for IW. As a result, the hot melt temperature for the adhesive experiments was set around 150 oC. The results indicate that Irvingia kernel extract is a more promising source of non-formaldehyde based adhesives in wood composite production.
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| 10. |
- Alexanderson, Petter
(författare)
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Adding Audibility - Reifying the Soundscape of Process Operators
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A contemporary challenge when designing interactive artifacts is to take into account the wealth of devices, systems, and tools people use every day - here termed an 'interaction ecology'. This thesis addresses three research issues. Firstly, the character of sound perception, and how auditory interaction can be applied to ubiquitous computing. Secondly, how everyday sounds make people aware of surrounding events and situations. Thirdly, the design-oriented issue of how to make use of sound as a medium for interaction. The first issue is addressed by means of a theoretical study of the character of auditory interaction and audio perception. Previous research indicates that sound is a sensitive and precise modality of interaction. The second issue is taken up through a qualitative study of the work practice of process operators, targeting how they ascribe meaning to sounds in their daily work environment. For the operators, the embodied experience of pumps, motors and driers in the plant area is crucial for the up-to-date understanding of process status and quality. During Participatory Soundscape Interpretation (PSI) sessions, operators listen to sound clips from the factory, and their thoughts about each clip are discussed. The operators make use of daily sounds for identifying things and places, for notification about status of surrounding artefacts, for maintaining social awareness, and for issues relating to learning and work timetables. Based on the findings from the factory case study, three design directions were explored during design workshops at the factory. A sound probing device was designed to be a personal device for gathering and collecting everyday sounds, and thereby to address temporal limitations of the sound medium. A sound repository concept elaborated on how to interact with sounds from a single source but from different points in time. With these two concepts, novel ways of collecting and accessing sounds over time were achieved. The third design concept dealt with being aware of multiple ongoing things of interest, and how to 'stay tuned' without being drowned in impressions. In a balanced interaction ecology, people are informed about the status of surrounding resources, can bear with and control the attention demands of surrounding artifacts, and experience the ongoing dialogue as well in hand. The balance of an interaction ecology and the creation of meaningful relations are the result of an ongoing interaction between people and artifacts. I argue that adding audibility will contribute to more balanced interaction ecologies.
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