| 1. |
- Abrahamsson, Lars, et al.
(författare)
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HVDC Feeder Solution for Electric Railways
- 2012
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Ingår i: IET Power Electronics. - 1755-4535 .- 1755-4543.
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Tidskriftsartikel (refereegranskat)abstract
- The railway power supply systems in many sparsely populated countries are relatively weak. Weak railway power supply systems causes problems with power quality, voltage drops, and high transmission losses.For AC railway power supply systems with a different frequency than the public grid, high-voltage AC (HVAC) transmission lines are common, connected to the catenary by transformers.In this paper an alternative design based on an HVDC feeder is suggested. The HVDC feeder 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 public frequency. The converter stations between the public grid and the HVDC feeder can be sparsely distributed, in the range of 100 km or more, whereas the converters connecting the HVDC feeder to the catenary are distributed with a much closer spacing. Their ratings can be lower than substation transformers or electro-mechanical converters, since the power flow can be fully controlled.Despite a relatively low power rating, the proposed converters can be highly efficient due to the use of medium frequency technology. The HVDC-based feeding system results in lower material usage, lower losses and higher controllability compared to present solutions.Simulations of the proposed solution show clear advantages regarding transmission losses and voltages compared to conventional systems, especially for cases with long distances between feeding points to the catenary, and when there are substantial amounts of regeneration from the trains.
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| 3. |
- Adamsson, Jenni, 1977, et al.
(författare)
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Gastric expression of IL-17A and IFNγ in Helicobacter pylori infected individuals is related to symptoms
- 2017
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Ingår i: Cytokine. - : Elsevier BV. - 1043-4666. ; 99, s. 30-34
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Tidskriftsartikel (refereegranskat)abstract
- Background: Chronic infection with Helicobacter pylori leads to gastritis and in a subpopulation of infected individuals to ulcers and cancer. Bacterial virulence factors and host immune inflammatory responses are risk factors related to disease. CD4+ T cells secrete cytokines that promote inflammation and an anti-bacterial response in the gastric mucosa during infection. The aim of the study was to investigate the pattern of expression of CD4+ T cell derived cytokines, IL-17A and IFNγ in paired antrum and corpus biopsies and correlate it to H. pylori infection outcome. Methods: Gene and protein expression of IL-17A and IFNγ was analyzed in gastric biopsies from H. pylori infected subjects with non-ulcer dyspepsia (NUD) or gastric ulcer; and for comparison uninfected individuals. Results: Upregulation of IL-17A and IFNγ gene expression was seen in corpus and antrum biopsies of H. pylori infected individuals with NUD compared to in uninfected controls. The expression of these cytokines correlated significantly with each other. Immunofluorescence staining revealed increased frequencies of IL-17A+ and IFNγ+ cells in antrum biopsies of gastric ulcer patients compared to of H. pylori infected NUD individuals; positive cells were not detected in any of the biopsies of uninfected controls. The frequencies of IFNγ and IL-17A+ cells correlated positively with inflammation in the antrum, but not the corpus, of H. pylori infected individuals. In the antrum, while there was no significant evidence of correlation between IFNγ and bacterial score, a positive correlation between bacterial score and IL-17A+ cells was seen. Conclusions: In H. pylori infected individuals, the frequencies of IFNγ and IL-17A+ cells were increased in the antrum, particularly in patients with H. pylori induced gastric ulcers. Even though H. pylori colonized both the corpus and antrum regions of the stomach, the cytokine responses and subsequent pathology were mainly detected in the antrum. © 2017 Elsevier Ltd
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| 4. |
- Adamsson, Jenni, 1977, et al.
(författare)
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Novel immunostimulatory agent based on CpG oligodeoxynucleotide linked to the nontoxic B subunit of cholera toxin.
- 2006
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Ingår i: Journal of immunology (Baltimore, Md. : 1950). - 0022-1767. ; 176:8, s. 4902-13
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we report the development of a novel, rationally designed immunostimulatory adjuvant based on chemical conjugation of CpG oligodeoxynucleotide (ODN) to the nontoxic B subunit of cholera toxin (CTB). We demonstrate that the immunostimulatory effects of CpG can be dramatically enhanced by conjugation to CTB. Thus, CpG ODN linked to CTB (CTB-CpG) was shown to be a more potent stimulator of proinflammatory cytokine and chemokine responses in murine splenocytes and human PBMCs than those of CpG ODN alone in vitro. The presence of CpG motif, but not modified phosphorothioate ODN backbone, was found to be critical for the enhanced immunostimulatory effects of CTB-CpG. Our mode-of-action studies, including studies on cells from specifically gene knockout mice suggest that similar to CpG, CTB-CpG exerts its immunostimulatory effects through a TLR9/MyD88- and NF-kappaB-dependent pathway. Surprisingly, and as opposed to CpG ODN, CTB-CpG-induced immunity was shown to be independent of endosomal acidification and resistant to inhibitory ODN. Furthermore, preincubation of CTB-CpG with GM1 ganglioside reduced the immunostimulatory effects of CTB-CpG to those of CpG ODN alone. Interestingly, conjugation of CpG ODN to CTB confers an enhanced cross-species activity to CpG ODN. Furthermore, using tetanus toxoid as a vaccine Ag for s.c. immunization, CTB-CpG markedly enhanced the Ag-specific IgG Ab response and altered the specific pattern of Ab isotypes toward a Th1 type response. To our knowledge, CTB is the first nontoxic derivative of microbial toxins discovered that when chemically linked to CpG remarkably augments the CpG-mediated immune responses.
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| 7. |
- 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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| 8. |
- Alawi, Omer A., et al.
(författare)
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Thermohydraulic performance of thermal system integrated with twisted turbulator inserts using ternary hybrid nanofluids
- 2023
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Ingår i: Nanotechnology Reviews. - : Walter de Gruyter. - 2191-9089 .- 2191-9097. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Mono, hybrid, and ternary nanofluids were tested inside the plain and twisted-tape pipes using k-omega shear stress transport turbulence models. The Reynolds number was 5,000 ≤ Re ≤ 15,000, and thermophysical properties were calculated under the condition of 303 K. Single nanofluids (Al2O3/distilled water [DW], SiO2/DW, and ZnO/DW), hybrid nanofluids (SiO2 + Al2O3/DW, SiO2 + ZnO/DW, and ZnO + Al2O3/DW) in the mixture ratio of 80:20, and ternary nanofluids (SiO2 + Al2O3 + ZnO/DW) in the mixture ratio of 60:20:20 were estimated in different volumetric concentrations (1, 2, 3, and 4%). The twisted pipe had a higher outlet temperature than the plain pipe, while SiO2/DW had a lower Tout value with 310.933 K (plain pipe) and 313.842 K (twisted pipe) at Re = 9,000. The thermal system gained better energy using ZnO/DW with 6178.060 W (plain pipe) and 8426.474 W (twisted pipe). Furthermore, using SiO2/DW at Re = 9,000, heat transfer improved by 18.017% (plain pipe) and 21.007% (twisted pipe). At Re = 900, the pressure in plain and twisted pipes employing SiO2/DW reduced by 167.114 and 166.994%, respectively. In general, the thermohydraulic performance of DW and nanofluids was superior to one. Meanwhile, with Re = 15,000, DW had a higher value of η Thermohydraulic = 1.678
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| 9. |
- Alexanderson, Petter, et al.
(författare)
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Being and mixing : designing interactive soundscapes
- 2006
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Ingår i: Proceedings of the 4th Nordic conference on Human-computer interaction. - New York, NY, USA : ACM. ; , s. 252-261
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Konferensbidrag (refereegranskat)abstract
- This paper describes a study of the auditory environment in a chemical factory, and how a group of process operators ascribe meaning to a selection of sound clips from their daily work environment. We argue for a design-oriented phenomenological approach to soundscape studies, and suggest an approach based on an exploration of how already occurring sounds are used. This knowledge will be used to inform the design of new useful auditory environments. Our study shows that the richness of the auditory environment is a crucial aspect of the distributed work environment. An important part of the design process is the operator’s contribution to the concepts suggested. From design workshops several design concepts aiming to explore and test different approaches for making sound affordances available have been developed. This has led us to a new understanding of how interactive soundscapes enable distributed awareness – what we refer to as ’Being and Mixing’.
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| 10. |
- Alimonti, P., et al.
(författare)
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Some APX-completeness results for cubic graphs
- 2000
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Ingår i: Theoretical Computer Science. - 0304-3975 .- 1879-2294. ; 237:2-Jan, s. 123-134
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Tidskriftsartikel (refereegranskat)abstract
- Four fundamental graph problems, Minimum vertex cover, Maximum independent set, Minimum dominating set and Maximum cut, are shown to be APX-complete even for cubic graphs. Therefore, unless P = NP, these problems do not admit any polynomial time approximation scheme on input graphs of degree bounded by three.
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