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| 2. |
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| 3. |
- Bolton, Kim, et al.
(författare)
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Carbon Nanotube Growth Mechanisms
- 2007
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Ingår i: Proceedings of Diamond 2007, the 18th European Conference on Diamond, Diamond-Like Materials, Carbon Nanotubes, Nitrides and Silicon Carbide.
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Konferensbidrag (refereegranskat)abstract
- We have used a variety of computational methods to study key aspects of single-walled carbon nanotube (SWNT) growth. Molecular dynamics (MD) studies based on an empirical force field showed; for example; why SWNT growth occurs in a temperature window and why; for 1-2 nm catalyst particles; the SWNT diameter varies linearly with the size of the particle. In addition; the liquid or solid phase of the catalyst particle is strongly dependent on particle size; and smaller particles (< 1.5 nm) are liquid at typical chemical vapor deposition temperatures whereas larger particles (> 5 nm) are solid. The phase of particles of intermediate sizes depends on the exact temperature and on their carbon content. The effect of substrates on metal-carbide properties and SWNT growth has been studied by combing density functional (DFT) and MD methods. A major effect of flat; inert substrates is to flatten the catalyst particles thereby increasing their melting points. DFT has also been used to study the catalyst-SWNT interaction which is critical for the growth of long SWNTs; and is also being used to study the importance of the SWNT cap structure on its chirality. This knowledge is important; for example; when using SWNTs as seeds for the growth of longer nanotubes.
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| 5. |
- Börjesson, Andreas, et al.
(författare)
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Altered proinsulin conversion in rat pancreatic islets exposed long-term to various glucose concentrations or interleukin-1{beta}
- 2007
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Ingår i: Journal of Endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 192:2, s. 381-387
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Tidskriftsartikel (refereegranskat)abstract
- In order to elucidate a possible relationship between beta-cell function and conversion of proinsulin to insulin, isolated rat pancreatic islets were maintained in tissue culture for 1 week at various glucose concentrations (5 x 6-56 mM). Studies were also conducted on islets cultured for 48 h with interleukin-1beta (IL-1beta). By pulse-chase labelling and immunoprecipitation, the relative contents of newly synthesized proinsulin and insulin were determined. ELISA was used to analyse insulin and proinsulin content in medium and within islets. Using real-time PCR, the mRNA levels of proinsulin converting enzymes (PC1 and PC2) were studied. Islets cultured at 56 mM glucose had an increased proportion of newly synthesized proinsulin when compared with islets cultured at 5 x 6 mM glucose after a 90-min chase periods, however, no difference was observed after culture at 11 and 28 mM glucose. ELISA measurements revealed that culture at increased glucose concentrations as well as islet exposure to IL-1beta increased proinsulin accumulation in the culture media. The mRNA expression of PC1 was increased after culture at 11 and 28 mM glucose. Treatment for 48 h with IL-1beta increased the proportion of proinsulin both at 45 and 90 min when compared with control islets. These islets also displayed a decreased mRNA level of PC1 as well as PC2. Calculations of the half-time for proinsulin demonstrated a significant prolongation after treatment with IL-1beta. We conclude that a sustained functional stimulation by glucose of islets is coupled to a decreased conversion of proinsulin which is also true for islets treated with IL-1beta. This may contribute to the elevated levels of proinsulin found both at the onset of type 1 diabetes as well as in type 2 diabetes.
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| 7. |
- Börjesson, Andreas, 1976-
(författare)
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Investigations of Strategies to Counteract Proinflammatory Cytokines in Experimental Type 1 Diabetes
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Type 1 diabetes (T1D) is a chronic autoimmune disease targeted against the pancreatic β-cells. Proinflammatory cytokines are considered to play a major role in the destruction of the insulin-producing β-cells. This thesis studied strategies to counteract proinflammatory cytokines in experimental T1D. Both animal models for T1D as well as β-cell preparations exposed in vitro to putative noxious conditions were examined.In the first study we observed that cytokine treatment of mouse pancreatic islets lacking inducible nitric oxide synthase (iNOS) induced a prolongation of the early stimulatory phase of glucose stimulated insulin secretion. Various experiments led to the conclusion that this prolonged stimulatory effect may involve the DAG/PLD/PKC pathway.Next, we transplanted mouse islets deficient in iNOS to spontaneously diabetic NOD mice. We observed a normalization of hyperglycemia but not a delayed allograft rejection compared to transplanted wild type islets. Thus, absence of iNOS in the graft was not sufficient to prolong allograft survival.In paper III we found that sustained glucose stimulation of rat pancreatic islets was coupled to a decreased conversion of proinsulin to insulin. Islet treatment with IL-1β was also coupled to a decreased proinsulin conversion. Islet proconvertase activity may be a target in islet damage.In paper IV prolactin (PRL) was administered to mice in the multiple low dose streptozotocin model and we observed that PRL enhanced a Th2 response. This may contribute to the protective action by PRL in this model of autoimmune T1D.Finally, by examining β-cells overexpressing Suppressor of cytokine signalling 3 (SOCS-3) it was found that this could inhibit IL-1β induced signalling through the NF-κB and MAPK pathways. SOCS-3 overexpression also inhibited apoptosis induced by cytokines in primary β-cells. Lastly, we demonstrated that SOCS-3 transgenic islets were protected in an allogeneic transplantation model.
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| 8. |
- Börjesson, Andreas, et al.
(författare)
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Survival of an islet allograft deficient in iNOS after implantation into diabetic NOD mice
- 2006
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Ingår i: Cell Transplantation. - 0963-6897 .- 1555-3892. ; 15:8-9, s. 769-775
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Tidskriftsartikel (refereegranskat)abstract
- Proinflammatory cytokines play a major role in rejection of pancreatic islet allografts and in type 1 diabetes (T1D). In rodent islets, exposure to IL-1β alone or combined with IFN-γ induces expression of inducible nitric oxide synthase (iNOS). Inhibition of iNOS or a deletion of the iNOS gene has been shown to be protective in animal models of T1D. In the present study we tested the hypothesis that transplantation of pancreatic islets deficient in iNOS (iNOS-/-) would permit increased graft survival. Pancreatic islets isolated from wild-type (wt) mice and iNOS-/- mice were allogeneically transplanted beneath the kidney capsule of spontaneously diabetic NOD mice. When blood glucose increased above 12.0 mM after preceding normalization of hyperglycemia, animals were sacrificed. Histological examinations of grafts were performed and graft gene expression was analyzed by real-time PCR. Transplantations of the two types of islets could reverse hyperglycemia and the grafts functioned for on average 1 week posttransplantation. Morphological examination of both types of islet grafts showed immune cell infiltration around and within the grafts. Remaining endocrine cells could be observed in wt and iNOS-/- islet grafts. In the removed grafts iNOS-/- islet tissue contained higher mRNA levels of insulin, proinsulin convertases (PC-1 and PC-2), and IL-1β compared to transplanted wt islets. The assessments of insulin, PC-1 and PC-2 mRNAs of the grafts suggest that the iNOS-/- islets may be more resistant to destruction in the transplantation model used; however, this was not sufficient to prolong the period of normoglycemia posttransplantation.
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| 10. |
- Börjesson, Stefan, et al.
(författare)
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A seasonal study of the mecA gene and Staphylococcus aureus including methicillin-resistant S. aureus in a municipal wastewater treatment plant
- 2009
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Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 43:4, s. 925-932
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Tidskriftsartikel (refereegranskat)abstract
- The spread of methicillin-resistant Staphylococcus aureus (MRSA), in which the mecA gene mediates resistance, threatens the treatment of staphylococcal diseases. The aims were to determine the effect of wastewater treatment processes on mecA gene concentrations, and the prevalence of S. aureus and MRSA over time. To achieve this a municipal wastewater treatment plant was investigated for the mecA gene, S. aureus and MRSA, using real-time PCR assays. Water samples were collected monthly for one year, at eight sites in the plant, reflecting different aspects of the treatment process. The mecA gene and S. aureus could be detected throughout the year at all sampling sites. MRSA could also be detected, but mainly in the early treatment steps. The presence of MRSA was verified through cultivation from inlet water. The concentration of the mecA gene varied between months and sampling sites, but no obvious seasonal variation could be determined. The wastewater treatment process reduced the mecA gene concentration in most months. Taken together our results show that the mecA gene, S. aureus and MRSA occur over the year at all sites investigated.
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| 12. |
- Börjesson, Stefan, et al.
(författare)
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Quantification of genes encoding resistance to aminoglycosides, beta-lactams and tetracyclines in wastewater environments by real-time PCR
- 2009
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Ingår i: International Journal of Environmental Health Research. - : Informa UK Limited. - 0960-3123 .- 1369-1619. ; 19:3, s. 219-30
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Tidskriftsartikel (refereegranskat)abstract
- In this study real-time PCR assays, based on the LUX-technique, were developed for quantification of genes mediating resistance to aminoglycosides [aac(6 ')-Ie + aph(2 ' ')], beta-lactams (mecA), and tetracyclines (tetA and tetB), for use in wastewater environments. The developed assays were applied on DNA extracted from three wastewater-associated environments: soil from an overland flow area treating landfill leachates, biofilm from a municipal wastewater treatment plant, and sludge from a hospital wastewater pipeline. The highest concentration of all genes was observed in the hospital pipeline and the lowest in the overland flow system. TetA and aac(6 ')-Ie + aph(2 ' ') could be detected in all environments. The tetB gene was detected in the overland flow area and the hospital wastewater pipeline and mecA was detected in the wastewater treatment plant and the hospital pipeline. The developed LUX real-time PCR assays were shown to be fast and reproducible tools for detection and quantification of the four genes encoding antibiotic resistance in wastewater.
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| 13. |
- Börjesson, Stefan, 1979-, et al.
(författare)
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Quantification of genes encoding resistance to aminoglycosides, β-lactams and tetracyclines in wastewater environments by real-time PCR
- 2009
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Ingår i: International Journal of Environmental Health Research. - : Taylor & Francis. - 0960-3123 .- 1369-1619. ; 19:3, s. 219-230
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Tidskriftsartikel (refereegranskat)abstract
- In this study real-time PCR assays, based on the LUX™-technique, were developed for quantification of genes mediating resistance to aminoglycosides [aac(6´′)-Ie + aph(2´′´′)], β-lactams (mecA), and tetracyclines (tetA and tetB), for use in wastewater environments. The developed assays were applied on DNA extracted from three wastewater-associated environments: soil from an overland flow area treating landfill leachates, biofilm from a municipal wastewater treatment plant, and sludge from a hospital wastewater pipeline. The highest concentration of all genes was observed in the hospital pipeline and the lowest in the overland flow system. TetA and aac(6´′)-Ie + aph(2´′´′) could be detected in all environments. The tetB gene was detected in the overland flow area and the hospital wastewater pipeline and mecA was detected in the wastewater treatment plant and the hospital pipeline. The developed LUX™ real-time PCR assays were shown to be fast and reproducible tools for detection and quantification of the four genes encoding antibiotic resistance in wastewater.
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| 14. |
- Galli, Raoul, et al.
(författare)
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En prosopografisk studie över konsthögskoleelever och konstnärer 1939-2005
- 2008
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Ingår i: Praktiske Grunde. - 1902-2271. ; :1, s. 18-45
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Den här artikeln ger några exempel på hur vi gått till väga för att samla in data om kollektiva konstnärsbanor. Vår ambition är att följa individerna från vaggan – via skolor – till konstfältet. I ett första huvudavsnitt koncentrerar vi oss på de elever som var inskrivna på Kungliga Konsthögskolan i Stockholm åren 1939 till 1986. Hur många förberedande konstutbildningar hade de gått innan de kom in på skolan? Hur många ansökningar lämnade de in innan de blev antagna? Var manliga elever mer framgångsrika än kvinnliga i att få stipendier och belöningar under skoltiden? Vad skiljer eleverna som utexaminerades under en period då konstfältet präglades av ”postmodernism” från eleverna som utexaminerades under en tidigare era märkt av ”efterkrigstidsmodernism”? I det andra huvudavsnittet lämnar vi skolans värld för att i stället koncentrera oss på verksamma – utexaminerade – konstnärer i det svenska konstfältet 1945-2005. Vi ställer delvis samma typ av frågor i denna del: var manliga konstnärer mer framgångsrika än kvinnliga i att få stipendier och belöningar efter skoltiden? Hur har stipendieutdelningen förändrats över tid? Avslutningsvis lyfter vi fram tidskrifter och kritiker som hade en central roll i hallstämplandet av svenska konstnärskap.
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| 15. |
- Hammar, Linus, et al.
(författare)
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Studier på småfisk vid Lillgrund vindpark : Effektstudier under konstruktionsarbeten och anläggning av gravitationsfundament
- 2008
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En betydande aspekt beträffande miljöpåverkan från havsbaserad vindkraft är potentiell störning av fisk under konstruktionsarbetet. För att förankra vindkraftverken i sjöbotten kan olika fundament användas. Många fundamentmodeller kräver pålningsarbeten och för dessa är det känt att fisk kan störas betydande över stora avstånd på grund av de höga ljudnivåer som uppstår vid anläggningsarbetet. En annan vanlig fundamentmodell är gravitationsfundament, där inget pålningsarbete behövs men däremot muddring och stenläggning. Till skillnad mot pålningsarbeten är det sedan tidigare inte känt huruvida gravitationsfundamentens muddring och stenläggning medför någon betydande påverkan på fisk i dess omgivning. Som en delstudie till den parallella Vindval-publikationen Miljömässig optimering av fundament för havsbaserad vindkraft har provtagningar av fiskförekomst utförts under anläggningen av gravitationsfundament vid Lillgrund vindpark. Provtagningarna, som utfördes med liten trål, omfattade endast småfisk – definierat som juvenil (ung) fisk samt småväxta fiskarter. Småfisk förväntas emellertid vara särskilt känslig mot den sedimentspridning som uppstår genom muddringsarbeten. Provtagningarna fördelades mellan tre fallstudier omfattande olika delar av konstruktionsarbetet; 1) långtidseffekter av muddring, 2) korttidseffekter av muddring, samt 3) direkteffekter av stenläggning. Studiens utförande baseras på den statistiska designen BACI (Before/After Control/Impact), där provtagningar utförs före och efter en förväntad påverkan, dels i det påverkade området och dels i ett opåverkat kontrollområde.Eftersom löst kalkrikt sediment i höga halter kan påverka syreupptaget hos småfisk kunde det teoretiskt sett förväntas att muddringsarbetet medfört en lokal reduktion av antal individer eller arter av fisk i närområdet. Resultatet visade dock inte några indikationer på att enskilda mudderverksamheter medfört några negativa trender i förekomsten av småfisk, varken 1 månad (fallstudie 1; närmsta avstånd 60 m) eller 1 dygn (fallstudie 2; närmsta avstånd 150 m) efter utförd muddring. En viktig slutsats är följaktligen att ingen småfisk, varken juveniler eller enskilda arter, uppvisade någon negativ trend 1 dygn efter muddringsverksamhet på ett avstånd av 150 m.Det buller som uppstår under stenläggningen kunde teoretiskt sett förväntas medföra en lokal reduktion av antal individer eller arter av fisk i närområdet. Resultatet under stenläggningen (fallstudie 3) visade för juvenil fisk en signifikant större minskning av antal arter i påverkansområdena (Lillgrund; c:a 60 och 200 m från det pågående anläggningsarbetet) jämfört med det opåverkade kontrollområdet. Beträffande adult (vuxen) småfisk visades att ökningen av antal individer och biomassa var signifikant mindre i påverkansområdena vid det pågående stenläggningsarbetet, jämfört med kontrollområdet. Detta överensstämmer med den multivariata analysen (MDS) där kontrollområdet skiljer sig från de båda påverkansområdena under efter-studien. Beaktansvärt är emellertid att ingen av analyserna antyder några skillnader mellan de två olika avstånden 60 och 200 m från stenläggningsarbetet, vilket pekar på att det enskilda stenläggningsarbetet inte är förklaringen till avvikelserna. Mer sannolikt är att konstruktionsarbetena vid Lillgrund som helhet, alternativt naturliga skillnader mellan Lillgrund och kontrollområdet, bidragit till de funna skillnaderna efter stenläggningen i fallstudie 3. De fiskarter som tydligast visade en större ökning i kontrollområdet är sjustrålig smörbult, storspigg, småspigg samt tångsnälla.
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| 16. |
- Karlsson, Maths, 1978, et al.
(författare)
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Structure of Proton-Conducting Alkali Thio-Hydroxogermanates
- 2008
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 1520-5002 .- 0897-4756. ; 20:19, s. 6014-6021
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Tidskriftsartikel (refereegranskat)abstract
- Using a combination of neutron diffraction, infrared spectroscopy, and first-principles calculations, we have investigated the structure of hydrated and dehydrated proton conducting alkali thio-hydroxogermanates of general formula M2GeS2(OH)2·yH2O (M = K, Rb, and Cs). The results show that the structure of hydrated and dry materials are basically the same, which confirms previous indications that the main effect of heating these materials is just a loss of water. We suggest that in the hydrated state the structure of these materials is built of dimers of thio-hydroxogermanate anions, with the water molecules acting as bridges between such dimers. In the dehydrated structure, the thio-hydroxogermanate anions instead form an extended network through the formation of interdimer hydrogen bonds through the −OH groups in the structure. The alkali ions are suggested to act as “space-fillers” in voids formed by the thio-hydroxogermanate anion dimers, in both the hydrated and the dehydrated state.
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