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- Christensen, P. W., et al.
(författare)
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Formulation and comparison of algorithms for frictional contact problems
- 1998
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Ingår i: International Journal for Numerical Methods in Engineering. - : John Wiley & Sons. - 0029-5981 .- 1097-0207. ; 42:1, s. 145-173
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents two algorithms for solving the discrete, quasi-static, small-displacement, linear elastic, contact problem with Coulomb friction. The algorithms are adoptions of a Newton method for solving B-differentiable equations and an interior point method for solving smooth, constrained equations. For the application of the former method, the contact problem is formulated as a system of B-differentiable equations involving the projection operator onto sets with simple structure; for the application of the latter method, the contact problem is formulated as a system of smooth equations involving complementarity conditions and with the non-negativity of variables treated as constraints. The two algorithms are numerically tested for two-dimensional problems containing up to 100 contact nodes and up to 100 time increments. Results show that at the present stage of development, the Newton method is superior both in robustness and speed. Additional comparison is made with a commercial finite element code.
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- Platz-Christensen, Jens Jörgen, et al.
(författare)
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Long, uniform Lactobacilli (Döderlein's Bacteria): a new risk factor for postoperative infection after first-trimester abortion.
- 1995
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Ingår i: Infectious diseases in obstetrics and gynecology. - 1064-7449. ; 3:3, s. 102-9
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Tidskriftsartikel (refereegranskat)abstract
- The production of hydrogen peroxide (H2O2) from different strains of lactobacilli in the vagina has been proposed to play one of the most important protective roles in the vaginal defense system. New data have, however, suggested that Döderlein's bacteria, with the morphological appearance of long lactobacilli, have a low production of H2O2 . The purpose of the present study was to correlate the morphology of lactobacilli with the incidence of infection following legal abortion.Seven hundred sixty-nine women with lactobacilli but without Chlamydia trachomatis or bacterial vaginosis in their vaginal wet smears who were to undergo legal abortions were divided into 6 different groups according to the morphological appearance of the lactobacilli. The postoperative infection rates in these different groups were compared. A phenotypic classification of some of the lactobacilli was performed.The presence of Döderlein's bacteria compared with a mixed flora of lactobacilli increased the risk of postoperative infection 3 times [relative risk (RR) = 3.0; 95% confidence interval (CI), 1.5-6.3]. After a logistic regression analysis, the only independent risk factors were the presence of Döderlein's bacteria and earlier gestational age.We found that the lactobacilli regarded as commensal organisms and "normal, healthy lactobacilli" in the vagina were present in only 18% of these women and that their presence might be hazardous. Therefore, we must reconsider our concept of the "normal" lactobacilli in the vaginal wet smears of healthy women.
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- Ratilainen, Tommi, 1970, et al.
(författare)
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Hybridization of peptide nucleic acid
- 1998
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Ingår i: Biochemistry. - : American Chemical Society (ACS). - 1520-4995 .- 0006-2960. ; 37:35, s. 12331-12342
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Tidskriftsartikel (refereegranskat)abstract
- The thermodynamics of hybridization and the conformations of decameric mixed purine-pyrimidine sequence PNA/PNA, PNA/DNA, and DNA/DNA duplexes have been studied using fluorescence energy transfer (FET), absorption hypochromicity (ABS), isothermal titration calorimetry (ITC), and circular dichroism (CD) techniques. The interchromophoric distances determined in the FET experiments on fluorescein- and rhodamine-labeled duplexes indicate that the solution structures of the duplexes are extended helices in agreement with available NMR (PNA/DNA) and crystal X-ray data (PNA/PNA). The melting thermodynamics of the duplexes was studied with both FET and ABS. The thermodynamic parameters obtained with ABS are in good agreement with the parameters from calorimetric measurements while FET detection of duplex melting gives in most cases more favorable free energies of hybridization. This discrepancy between FET and ABS detection is ascribed to the conjugated dyes which affect the stability of the duplexes substantially. Especially, the dianionic fluorescein attached via a flexible linker either to PNA or to DNA seems to be involved in an attractive interaction with the opposite dicationic lysine when hybridized to a PNA strand. This interaction leads to an increased thermal stability as manifested as a 3-4 degrees C increase of the melting temperature. For the PNA/DNA duplex where fluorescein is attached to the PNA strand, a large destabilization (Delta T-m = -12 degrees C) occurs relative to the unlabeled duplex, probably originating from electrostatic repulsion between the fluorescein and the negatively charged DNA backbone. In the case of the PNA/PNA duplex, the sense of helicity of the duplex is reversed upon conjugation of fluorescein via a flexible linker arm, but not when the fluorescein is attached without a linker to the PNA.
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