| 11. |
- James, S, et al.
(författare)
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Luminescence control in the marine bacterium Vibrio fischeri: An analysis of the dynamics of lux regulation
- 2000
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 1089-8638 .- 0022-2836. ; 296:4, s. 1127-1137
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Tidskriftsartikel (refereegranskat)abstract
- A mathematical model has been developed based on the fundamental properties of the control system formed by the lux genes and their products in Vibrio fischeri. The model Clearly demonstrates how the components of this system work together to create two, stable metabolic states corresponding to the expression of the luminescent and non-luminescent phenotypes. It is demonstrated how the cell can "switch" between these steady states due to changes in parameters describing metabolic processes and the extracellular concentration of the signal molecule N-3-oxohexanoyl-L-homoserine lactone. Ln addition, it is shown how these parameters influence how sensitive the switch mechanism is to cellular LuxR and N-3-oxohexanoyl-L-homoserine lactone and complex concentration. While these properties could lead to the collective phenomenon known as quorum sensing, the model also predicts that under certain metabolic circumstances, basal expression of the lux genes could cause a cell to luminesce in the absence of extracellular signal molecule. Finally, the model developed in this study provides a basis for analysing the impact of other levels of control upon lux regulation. (C) 2000 Academic Press.
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| 12. |
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| 13. |
- Spolaore, M., et al.
(författare)
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Vortex-induced diffusivity in reversed field pinch plasmas
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:21
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Tidskriftsartikel (refereegranskat)abstract
- Coherent structures identified in two reversed field pinch experiments are interpreted as a dynamic balance of dipolar and monopolar vortices growing and evolving under the effect of the ExB flow shear. For the first time their contribution to the anomalous transport has been estimated in fusion related plasmas, showing that they can account for up to 50% of the total plasma diffusivity. The experimental findings indicate that the diffusion coefficient associated with the coherent structures depends on the relative population of the two types of vortices and is minimum when the two populations are equal. An interpretative model is proposed to explain this feature.
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| 14. |
- Aspholm-Hurtig, Marina, et al.
(författare)
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Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
- 2004
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Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 305:5683, s. 519-22
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Tidskriftsartikel (refereegranskat)abstract
- Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations.
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| 15. |
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| 16. |
- Carpenter, Lucy M, et al.
(författare)
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Independent effects of reported sexually transmitted infections and sexual behavior on HIV-1 prevalence among adult women, men, and teenagers in rural Uganda
- 2002
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Ingår i: Journal of Acquired Immune Deficiency Syndromes. - 1525-4135 .- 1944-7884. ; 29:2, s. 174-180
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To assess whether sexually transmitted infections (STIs) and sexual behavior are independently associated with HIV-1 among adult women, men, and teenagers in rural Uganda. DESIGN: Cross-sectional survey. METHODS: All adults (13 years and older) residing in 18 communities were invited to participate. HIV status was determined from serum samples and data collected during confidential interview. Independent effects of risk factors for HIV were estimated using adjusted odds ratios (ORs) with 95% confidence intervals (CIs) from logistic regression. RESULTS: Women reporting genital ulcers in the last 12 months were over twice as likely to be HIV positive after adjustment for sociodemographic factors and number of lifetime sexual partners (OR, 2.5; 95% CI, 1.9-3.4). Equivalent associations were stronger for men (OR, 3.2; 95% CI, 2.2-4.7) but weaker for teenagers (OR, 2.0, 95% CI, 0.5-8.7). Number of lifetime sexual partners was associated ( p <.05) with HIV status for women, men, and teenagers independently of reported genital ulcers. Teenagers reporting casual partners were over four times ( p <.001), and men reporting condom use almost twice ( p <.001), as likely to be HIV positive. Neither history of genital discharge nor other measures of sexual behavior were independently related to HIV status. CONCLUSION: Reported STIs and sexual behavior are independently associated with HIV in rural Uganda. Community-based interventions to reduce HIV should target both and should include teenagers.
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| 17. |
- Cecconello, Marco, et al.
(författare)
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Current profile modification experiments in EXTRAP T2R
- 2004
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 0741-3335 .- 1361-6587. ; 46:1, s. 145-161
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Tidskriftsartikel (refereegranskat)abstract
- Pulsed poloidal current drive (PPCD) experiments have been conducted in the resistive shell EXTRAP T2R reversed-field pinch experiment. During the current profile modification phase, the fluctuation level of the m = 1 internally resonant tearing modes decreases, and the velocity of these modes increases. The m = 0 modes are not affected during PPCD, although termination occurs with a burst in the m = 0 amplitude. The PPCD phase is characterized by an increase in the central electron temperature (up to 380 eV) and in the soft x-ray signal. Spectroscopic observations confirm an increase in the central electron temperature. During PPCD, the plasma poloidal beta increases to 14%, and the estimated energy confinement time doubles, reaching 380 mus. The reduction in the fluctuation level and the corresponding increase in the energy confinement time are qualitatively consistent with a reduction in parallel transport along stochastic magnetic field lines.
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| 18. |
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| 19. |
- Esteller, Manel, et al.
(författare)
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DNA methylation patterns in hereditary human cancers mimic sporadic tumorigenesis
- 2001
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 10:26, s. 3001-3007
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Tidskriftsartikel (refereegranskat)abstract
- Cancer cells have aberrant patterns of DNA methylation including hypermethylation of gene promoter CpG islands and global demethylation of the genome. Genes that cause familial cancer, as well as other genes, can be silenced by promoter hypermethylation in sporadic tumors, but the methylation of these genes in tumors from kindreds with inherited cancer syndromes has not been well characterized. Here, we examine CpG island methylation of 10 genes (hMLH1, BRCA1, APC, LKB1, CDH1, p16(INK4a), p14(ARF), MGMT, GSTP1 and RARbeta2) and 5-methylcytosine DNA content, in inherited (n = 342) and non-inherited (n = 215) breast and colorectal cancers. Our results show that singly retained alleles of germline mutated genes are never hypermethylated in inherited tumors. However, this epigenetic change is a frequent second "hit", associated with the wild-type copy of these genes in inherited tumors where both alleles are retained. Global hypomethylation was similar between sporadic and hereditary cases, but distinct differences existed in patterns of methylation at non-familial genes. This study demonstrates that hereditary cancers "mimic" the DNA methylation patterns present in the sporadic tumors.
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| 20. |
- Helgesson, Johan, et al.
(författare)
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Finite Size scaling and the nuclear liquid-gas phase transition
- 2003
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Konferensbidrag (refereegranskat)abstract
- Recent analyses of multifragmentation data in terms of Fisher's model have led to the estimate of the coexistence curve of finite nuclear matter as well as of the location of the critical point. In order to extrapolate those results to infinite nuclear matter, finite size effects have to be taken into account. Guided by the finite size behavior of the three-dimensional Ising model, we propose a modified Fisher Droplet model expression that incorporates surface and correlation length effects.
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