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- Abel, Frida, 1974
(författare)
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Genetic studies of neuroblastoma with emphasis on the apoptotic pathway
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aim: The objective of this thesis was to find genes and chromosomal regions involved in neuroblastoma (NB) tumor progression. NB is a childhood tumor of the sympathetic nervous system that generally occurs spontaneously. Biologically, NB has a complex heterogeneity from tumor progression to tumor regression, dependent on clinical stage and age at diagnosis. The main genetic markers, which are also of prognostic value in NB, are amplification of the oncogene MYCN, deletion of chromosome arm 1p and gain of chromosome arm 17q. Results: We have been shown using fluorescence in situ hybridization (FISH) on a Scandinavian tumor material, that 17q gain is present in approximately 65% of all NB stages, is significantly associated with poor prognosis and predicts survival. The gene encoding somatostatin receptor 2 (SSTR2), localized in chromosome region 17q24, was not found to be mutated in any NB, when analyzed with PCR-based single stranded conformation polymorphism/heteroduplex (SSCP/HD) and DNA sequencing. In a tentative effort of defining of the location of a general embryonal tumor suppressor gene (TSG) on 1p, we combined the smallest region of overlap (SRO) of 1p deletions in NB tumors and germ cell tumors (GCTs). We thus delimited the NB/GCT SRO to approximately 5 cM between markers D1S508 and D1S244, and fine-mapped this region by radiation hybrid mapping and construction of a bacterial artificial chromosome (BAC) contig. A homozygously deleted region in an NB cell line was found to partially overlap the proximal part of the 5 cM-SRO defined by us, which further focused our search for a TSG to a 500 kb candidate region in 1p36.22. Two attractive candidate NB TSGs, DFFA and CASP9, are both located in 1p36.2 and encode key apoptotic mediators. In fact, DFFA resides in the 500 kb TSG candidate region. Via sequence analysis of the entire tumor material, we found three different coding alterations in DFFA which all affect the highly conserved N-terminal regulatory domain of DFF45. Using RT-PCR and real-time RT-PCR (TaqMan) studies, we were able to show that both DFFA and CASP9 are preferably expressed in NB tumors with favorable outcome. It has been proposed that lack of apoptosis plays an important role in tumor progression. We therefore screened an array with cDNAs involved in the apoptotic process, to find genes differentially expressed in NB tumors with unfavorable versus favorable biology. Using real-time RT-PCR analysis, we verified the differential expression of several transcripts encoding mitochondrial apoptotic mediators. Conclusions: We have shown that 17q gain is the most frequently detected alteration in NB and that it is associated with established prognostic factors. We narrowed down the TSG candidate region on 1p and found mutations in a gene localized in the region possessing fundamental functions in apoptosis. Our results also suggest that the mitochondrial apoptotic pathway is suppressed at multiple steps in advanced stages of NB tumors, due to imbalance between anti-apoptotic and pro-apoptotic mediators.
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| 2. |
- Abou-Ali, Hala, 1972, et al.
(författare)
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Evaluating the welfare effects of improved water qualityusing the choice experiment method
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This paper analyzes the welfare effects of improved health status through increased water quality using a choice experiment. The survey was administered to a random sample of households in metropolitan Cairo, Egypt. We apply a random parameter logit model in the analysis and illustrate the richness of information that can be obtained from this type of model by estimating individual level willingness to pay (WTP). We find a significant WTP for improved health status, both for short-run and long-run health effects. However, the estimated WTP is fairly low compared with the costs of a program that would achieve these improvements.
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| 4. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Interpreting black hole QPOs
- 2004
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Ingår i: AIP Conference Proceedings. - 0094-243X. ; 714, s. 21-28
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- n all the microquasars with two hHz QPOs, the ratio of the frequencies is 3:2, supporting our suggestion that a non-linear resonance between two modes of oscillation in the accretion disk plays a role in exciting the observed modulations of the X-ray flux. We discuss the evidence in favor of this interpretation, and we relate the black hole spin to the frequencies expected for various types of resonances that may occur in nearly Keplerian disks in strong gravity. For those microquasars where the mass of the central X-ray source is known, the black hole spin can be deduced from a comparison of the observed and expected frequencies.
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| 5. |
- Abramowicz, Marek A, 1945, et al.
(författare)
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Twin peak QPOs frequencies in microquasars and Sgr A*. The resonance and other orbital models
- 2004
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Ingår i: Proceedings of RAGtime 4/5 Workshops on black holes and neutron stars, 14-16/13-15 October 2002/2003. - 8072482424
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In all four microquasars which show twin peak kHz QPOs, the ratio of the two frequencies is 3:2. This rather strongly supports the suggestion by Abramowicz, M. A. and Kluzniak [W. Abramowicz, M. A. and Kluzniak, W., (2001). A precise determination of black hole spin in GRO J1655-40. Astronomy and Astrophysics, 374:L19] that twin peak kHz QPOs are due to a resonance between some modes of accretion disk oscillations. Detailed studies of this suggestion revealed that several such non-linear resonances are present in nearly Keplerian disks in strong gravity. Here, we fit to observations predictions of the resonance hypothesis for two particular types of non-linear resonances between vertical and radial epicyclic frequencies. For three microquasars with known masses, the fits give an accurate estimate of the spin.
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| 7. |
- Adelbratt, Thomas, 1949
(författare)
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Beliefs about real life decision strategies
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- What kind of behavior is seen as most adaptive for everyday decision makers? How do they invest their mental energy? Is it in complex information integration, which traditionally is considered rational, or in other cognitive procedures? With these underlying questions 25 subjects were encouraged to give written accounts of their decision strategies in real life. The instructions promoted sequential descriptions without being too obtrusive. All reports were contents analyzed and condensed to six reflective and six intuitive categories with contrasting qualities. These indicated that the subjects had good analytic intentions, but rarely employed any demanding strategies and were almost unaware of the possibility of using different integration rules. The subjects rather preferred other sorts of deliberation, in areas like strategic planning, social adjustment, value co-ordination, and assessment calibration. Several of these activities were focused on evaluative phenomena and quite often prepared for systematic restructuring of values, criterion levels, and attribute weights to simplify the process. A strong regulating factor was the intuitive influence from emotions, established principles, identity concepts, and wishful thinking. It is concluded that the relative priority of evaluative phenomena has certain advantages for the individual. The strategy is probably easier to understand and to justify. It has a more natural relation to fundamental needs, identity aspects, social ties, etc. Finally, it is in direct contact with the individual?s emotional life and thus a connecting bridge between analysis and intuition.
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