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- Andersson, Mikael, et al.
(författare)
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The Influence of the Degree of Cross-linking, Type of Ligand and Support on the Chemical Stability of Chromatography Media Intended for protein Purification
- 1998
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Ingår i: Process Biochemistry. - 1359-5113 .- 1873-3298. ; 33:1, s. 47-55
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Tidskriftsartikel (refereegranskat)abstract
- The release of organic compounds from different liquid chromatography media in static conditions has been analysed with a total organic carbon (TOC) analyser. TOC results show that chemical stability increases with the degree of cross-linking in agarose beaded chromatography media and thus extend the working pH-range of the media. Of the unsubstituted chromatography media investigated, Sepharose® 6B, Sepharose CL-6B, Sepharose 4 Fast Flow, Sepharose 6 Fast Flow and Sepharose High Performance, the latter was the most stable medium. Sepharose High Performance releases only about 0·06% of its total carbon content after 1 week in 0·01 m HCl. Agarose beads are more stable to basic conditions (pH 14) compared with acidic conditions (pH 2). From UV spectroscopic and gel filtration results it was found that all Sepharose media release low amounts of 5-(hydroxymethyl)-2-furaldehyde and agarose fragments in acidic conditions. To investigate the effect of different ligands on chemical stability Q Sepharose 6 Fast Flow, DEAE Sepharose 6 Fast Flow, SP Sepharose 6 Fast Flow, CM Sepharose 6 Fast Flow, Phenyl Sepharose 6 Fast Flow, Octyl Sepharose 4 Fast Flow media were also studied under static conditions. In basic conditions it was found that all these chromatography media release carbon compounds to a higher extent than the unsubstituted Sepharose support. In addition, Hofmann elimination of Q and DEAE groups contributes to the decrease in the carbon content of the corresponding anion exchangers. During exposure to acidic conditions (pH 2) the release of carbon compounds was lower than the release from the support to which the ligands were coupled. The exceptions are Octyl Sepharose 4 Fast Flow and SP Sepharose 6 Fast Flow. In the case of Octyl Sepharose 4 Fast Flow, the ligand did not seem to influence chemical stability, whereas the SP group increases the degradation of the Sepharose support. In the case of SP Sepharose 6 Fast Flow the stability in acidic conditions can be improved by increasing the ionic strength. Anion exchangers based on different support polymers (agarose-, polystyrene-, methacrylate- and polyvinyl-based matrixes) were studied under static conditions. Agarose-based anion exchanger was the most stable in basic conditions (pH 14). In acidic conditions (pH 2) the chemical stability was about the same for many different anion exchangers.
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| 4. |
- Christiansson, Marie-Therese, et al.
(författare)
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En inter-organisatorisk förändringsanalys : utveckling av kund-/leverantörsprocessen
- 1997
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Konferensbidrag (refereegranskat)abstract
- Dagens sätt att göra affärer innebär ett ökat partnerskap och ett ökat datautbyte mellan organisationer i sökandet efter effektivitet och konkurrensfördelar. Affärsrelationer mellan leverantörer och kunder är beroende av att informationen flödar på ett strukturerat sätt mellan deras organisationer för att tillgodose respektive parts informationsbehov, dvs inter-organisatoriska informationssystem (IOIS). En metodutveckling pågår inom VINST-projektet där målet är att utveckla kunskap om och utforma en användbar metod som stöd vid verksamhetsutveckling av inter-organisatorisk karaktär. Denna rapport bygger på en metodprövande aktionsforskning vid en gemensam förändringsanalys som PartnerTech AB och en av deras kunder bedrivit med stöd av FA/SIMMetoden. Den metodtillämpning och metodutveckling som skett analyseras och diskuteras utifrån frågorna; hur en leverantör tillsammans med kunden kan utveckla den gemensamma kund-leverantörsprocessen och hur verksamhetsutvecklare kan använda FA/SIMM för att kartlägga och driva förbättring av inter-organisatoriska processer. Rapporten pekar bl a på behov av anpassade projektstrategier, arbetsformer och notation samt metodkomponenter för interaktionsanalys och uppföljning av åtgärder.
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| 6. |
- Collin, Peter, et al.
(författare)
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Lateral-torsional buckling of continuous bridge girders
- 1998
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Ingår i: Journal of constructional steel research. - 0143-974X .- 1873-5983. ; 45:2, s. 217-235
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Tidskriftsartikel (refereegranskat)abstract
- The resistance of bridge girders with respect to lateral-torsional buckling at support is strongly influenced by the moment gradient. In most design methods this influence is taken into account by the use of a correct critical bending moment in the slenderness parameter λ. This critical moment is influenced by the shape of the moment diagram as well as the distortion of the cross-section and the restraint from the web and stiffeners, if any. In this paper, a method for the calculation of the critical moment is presented. A further effect of the moment gradient is that the stresses due to lateral bending of the flange in connection with lateral-torsional buckling does not coincide with the maximum of stresses caused by bending in the vertical plane. This is taken into account by performing the check for lateral-torsional buckling in a design section at some distance from the support. A design procedure based on this concept has been introduced in Eurocode 3 Part 2: Steel Bridges
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| 7. |
- Corthay, Alexandre, et al.
(författare)
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Collagen-induced arthritis development requires alpha beta T cells but not gamma delta T cells: studies with T cell-deficient (TCR mutant) mice
- 1999
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Ingår i: International Immunology. - 1460-2377. ; 11:7, s. 1065-1073
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Tidskriftsartikel (refereegranskat)abstract
- Collagen type II (CII)-induced arthritis (CIA) in mice is a model for rheumatoid arthritis (RA) in which the role of T lymphocytes remains controversial. To clarify this, we have bred a targeted gene deletion of TCR beta or delta loci into two mouse strains susceptible to CIA, the B10.Q and DBA/1 strains. The TCRbeta-/- mice lacked alphabeta T cells, which was compensated by an expansion of B cells, gammadelta T cells and NK cells. The beta-/- mice, but not control beta+/- littermates, were completely resistant to CIA. The production of anti-CII IgG antibodies was also abolished in beta-/- mice, revealing a strict alphabeta T cell dependency. In contrast, beta-/- mice produced reduced, but significant, anti-CII IgM titers after immunization with either CII or ovalbumin, indicating a multispecificity for these alphabeta T cell-independent IgM antibodies. The TCRdelta-/- mice lacked gammadelta T cells but had no other significant changes in lymphocyte or monocyte subsets. The cytokine response (IL-2, IL-4, IL-10 and IFN-gamma) in delta-/- mice, quantified by flow cytometry staining of mitogen-stimulated lymphocytes, was indistinguishable from normal mice. Likewise, no statistically significant differences were observed in CIA between mice lacking gammadelta T cells and control littermates, considering arthritis incidence, day of disease onset, maximum arthritic score, anti-CII IgG titers and disease course. We conclude that alphabeta T cells are necessary for CIA development and for an IgG response towards CII, whereas gammadelta T cells are neither necessary nor sufficient for development of CIA.
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| 10. |
- Hedlund, Sven, et al.
(författare)
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PWLTool - a Matlab Toolbox for Piecewise Linear System
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This manual describes a Matlab toolbox for computational analysis of piecewise linear systems. Key features of the toolbox are modeling, simulation, analysis, and optimal control for piecewise linear systems. The simulation routines detect sliding modes and simulate equivalent dynamics. The analysis and design are based on computation of piecewise quadratic Lyapunov functions. The computations are performed using convex optimization in terms of linear matrix inequalities (LMIs).
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