| 1. |
- Ahlgren, Per
(author)
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The effects of indexing strategy-query term combination on retrieval effectiveness in a Swedish full text database
- 2004
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Doctoral thesis (other academic/artistic)abstract
- This thesis deals with Swedish full text retrieval and the problem of morphological variation of query terms in the document database. The study is an information retrieval experiment with a test collection. While no Swedish test collection was available, such a collection was constructed. It consists of a document database containing 161,336 news articles, and 52 topics with four-graded (0, 1, 2, 3) relevance assessments. The effects of indexing strategy-query term combination on retrieval effectiveness were studied. Three of five tested methods involved indexing strategies that used conflation, in the form of normalization. Further, two of these three combinations used indexing strategies that employed compound splitting. Normalization and compound splitting were performed by SWETWOL, a morphological analyzer for the Swedish language. A fourth combination attempted to group related terms by right hand truncation of query terms. A search expert performed the truncation. The four combinations were compared to each other and to a baseline combination, where no attempt was made to counteract the problem of morphological variation of query terms in the document database. Two situations were examined in the evaluation: the binary relevance situation and the multiple degree relevance situation. With regard to the binary relevance situation, where the three (positive) relevance degrees (1, 2, 3) were merged into one, and where precision was used as evaluation measure, the four alternative combinations outperformed the baseline. The best performing combination was the combination that used truncation. This combination performed better than or equal to a median precision value for 41 of the 52 topics. One reason for the relatively good performance of the truncation combination was the capacity of its queries to retrieve different parts of speech. In the multiple degree relevance situation, where the three (positive) relevance degrees were retained, retrieval effectiveness was taken to be the accumulated gain the user receives by examining the retrieval result up to given positions. The evaluation measure used was nDCG (normalized cumulated gain with discount). This measure credits retrieval methods that (1) rank highly relevant documents higher than less relevant ones, and (2) rank relevant (of any degree) documents high. With respect to (2), nDCG involves a discount component: a discount with regard to the relevance score of a relevant (of any degree) document is performed, and this discount is greater and greater, the higher position the document has in the ranked list of retrieved documents. In the multiple degree relevance situation, the five combinations were evaluated under four different user scenarios, where each scenario simulated a certain user type. Again, the four alternative combinations outperformed the baseline, for each user scenario. The truncation combination had the best performance under each user scenario. This outcome agreed with the performance result in the binary relevance situation. However, there were also differences between the two relevance situations. For 25 percent of the topics and with regard to one of the four user scenarios, the set of best performing combinations in the binary relevance situation was disjunct from the set of best performing combinations in the multiple degree relevance situation. The user scenario in question was such that almost all importance was placed on highly relevant documents, and the discount was sharp. The main conclusion of the thesis is that normalization and right hand truncation (performed by a search expert) enhanced retrieval effectiveness in comparison to the baseline, irrespective of which of the two relevance situations we consider. Further, the three indexing strategy-query term combinations based on normalization were almost as good as the combination that involves truncation. This holds for both relevance situations.
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| 2. |
- Al-Khalili, A, et al.
(author)
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Dissociative recombination cross section and branching ratios of protonated dimethyl disulfide and N-methylacetamide
- 2004
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In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:12, s. 5700-5708
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Journal article (peer-reviewed)abstract
- Dimethyl disulfide (DMDS) and N-methylacetamide are two first choice model systems that represent the disulfide bridge bonding and the peptide bonding in proteins. These molecules are therefore suitable for investigation of the mechanisms involved when proteins fragment under electron capture dissociation (ECD). The dissociative recombination cross sections for both protonated DMDS and protonated N-methylacetamide were determined at electron energies ranging from 0.001 to 0.3 eV. Also, the branching ratios at 0 eV center-of-mass collision energy were determined. The present results give support for the indirect mechanism of ECD, where free hydrogen atoms produced in the initial fragmentation step induce further decomposition. We suggest that both indirect and direct dissociations play a role in ECD.
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| 3. |
- Aspholm-Hurtig, Marina, et al.
(author)
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Functional adaptation of BabA, the H. pylori ABO blood group antigen binding adhesin.
- 2004
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In: 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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Journal article (peer-reviewed)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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| 4. |
- Broomé, Michael, et al.
(author)
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Pressure-independent cardiac effects of angiotensin II in pigs.
- 2004
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In: Acta Anaesthesiol Scand. - 0001-6772 .- 1365-201X. ; 182:2, s. 111-9
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Journal article (peer-reviewed)abstract
- BACKGROUND: Angiotensin II (Ang II) is a potent vasoconstrictor with an important role in the development of cardiovascular disease. Earlier results have shown a positive acute inotropic effect of Ang II in anaesthetized pigs together with significant vasoconstriction. This investigation was designed to study cardiac effects of Ang II, when blood pressure was maintained constant by experimental means. METHODS: Ang II (200 microg h(-1)) was infused in anaesthetized pigs (n = 10) at two different arterial blood pressures, the first determined by the effects of Ang II alone, and the second maintained at baseline blood pressure with nitroprusside. Cardiac systolic and diastolic function was evaluated by analysis of left ventricular pressure-volume relationships. RESULTS: Heart rate, end-systolic elastance (Ees) and pre-load adjusted maximal power (PWRmax EDV(-2)) increased at both blood pressure levels, although less when blood pressure was kept constant with nitroprusside. The time constant for isovolumetric relaxation (tau(1/2)) was prolonged with Ang II alone and shortened with Ang II infused together with nitroprusside. CONCLUSION: Ang II infusion in the pig has inotropic and chronotropic properties independent of arterial blood pressure levels, although the effects seem to be blunted by pharmacological actions of the nitric oxide donor nitroprusside.
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| 5. |
- Bränden, Petter
(author)
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On operators on polynomials preserving real-rootedness and the Neggers-Stanley conjecture
- 2004
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In: Journal of Algebraic Combinatorics. - 0925-9899 .- 1572-9192. ; 20:2, s. 119-130
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Journal article (peer-reviewed)abstract
- We refine a technique used in a paper by Schur on real-rooted polynomials. This amounts to an extension of a theorem of Wagner on Hadamard products of Polya frequency sequences. We also apply our results to polynomials for which the Neggers-Stanley Conjecture is known to hold. More precisely, we settle interlacing properties for E-polynomials of series-parallel posets and column-strict labelled Ferrers posets.
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| 6. |
- Dincbas-Renqvist, Vildan, et al.
(author)
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Thermodynamics of folding, stabilization, and binding in an engineered protein--protein complex.
- 2004
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In: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 126:36, s. 11220-30
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Journal article (peer-reviewed)abstract
- We analyzed the thermodynamics of a complex protein-protein binding interaction using the (engineered) Z(SPA)(-)(1) affibody and it's Z domain binding partner as a model. Free Z(SPA)(-)(1) exists in an equilibrium between a molten-globule-like (MG) state and a completely unfolded state, wheras a well-ordered structure is observed in the Z:Z(SPA)(-)(1) complex. The thermodynamics of the MG state unfolding equilibrium can be separated from the thermodynamics of binding and stabilization by combined analysis of isothermal titration calorimetry data and a separate van't Hoff analysis of thermal unfolding. We find that (i) the unfolding equilibrium of free Z(SPA)(-)(1) has only a small influence on effective binding affinity, that (ii) the Z:Z(SPA)(-)(1) interface is inconspicuous and structure-based energetics calculations suggest that it should be capable of supporting strong binding, but that (iii) the conformational stabilization of the MG state to a well-ordered structure in the Z:Z(SPA)(-)(1) complex is associated with a large change in conformational entropy that opposes binding.
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| 7. |
- Eklöf, Mats, 1953, et al.
(author)
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Feedback of workplace data to individual workers, workgroups or supervisors as a way to stimulate working environment activity: a cluster randomized controlled study.
- 2004
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In: International archives of occupational and environmental health. - : Springer Science and Business Media LLC. - 0340-0131 .- 1432-1246. ; 77:7, s. 505-14
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Journal article (peer-reviewed)abstract
- OBJECTIVE: To test whether feedback and discussion of ergonomic and psychosocial working-environment data during one short session with individual, groups or supervisors of white-collar computer workers had an effect on activity to modify workplace design, working technique and psychosocial aspects of work. METHODS: A total of 36 workgroups from nine organizations representing different trades was randomized (stratified for organization) to three feedback conditions or control with no feedback. Data were collected 1 month before and 6 months after feedback sessions. The effects studied were: (1) change in the proportion of workgroup members who reported any modification regarding workplace design or working technique; (2) change in the proportion of workgroup members who reported any modification regarding psychosocial aspects; (3) average number of modification types regarding workplace design or working technique per individual in a workgroup; (4) average number of modification types regarding psychosocial aspects per individual in a workgroup. RESULTS: All feedback conditions differed positively from controls regarding change in the proportion of workgroup members who reported any modification in workplace design or working technique. No such effect was found for psychosocial aspects. For change in average number of psychosocial modification types per individual in a workgroup an effect was observed for feedback to supervisors. No intervention effect was observed for the average number of modifications in workplace design or working technique per individual in a workgroup. CONCLUSION: Feedback and discussion of ergonomic and psychosocial working-environment data during one short session with individual, groups or supervisors of white-collar computer workers may have a positive effect on how many people in a workgroup modify (or have modifications done regarding) workplace design and working technique. Feedback to supervisors may have an effect on the average number of psychosocial modification types per individual in a workgroup. Feedback to group supervisors appeared to be the most cost-effective variant.
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| 8. |
- Ellmann, A, et al.
(author)
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Radiative lifetime of a bound excited state of Te-
- 2004
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:25, s. 253002-
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Journal article (peer-reviewed)abstract
- We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) P-2(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.
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| 9. |
- Fritioff, Karin, et al.
(author)
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Observation of an excited C2-4 ion
- 2004
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In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 37:11, s. 2241-2246
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Journal article (peer-reviewed)abstract
- This paper reports an experimental investigation of the electron impact detachment of C−4. We observe structure in the electron impact cross section for detaching a single electron from a C−4 cluster anion, which we attribute to the formation and decay of the C2−4 dianion. The system is energetically unstable and very rapidly decays via double autodetachment. The energy and width of the resonance were determined to be 8.8(5) eV and 1.4(5) eV, respectively, and the resonance lies 1.5(5) eV above the ground state of the neutral system. The experiment was conducted by merging monoenergetic electron and ion beams in the heavy ion storage ring CRYRING. The detachment channel was monitored by detecting neutral C4 fragments.
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| 10. |
- Fritioff, K, et al.
(author)
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Single and double detachment from H-
- 2004
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In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 69:4, s. 042707-
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Journal article (peer-reviewed)abstract
- Absolute cross sections for single and double detachment from H- following electron impact have been measured over a range of collision energies from the thresholds to 170 eV. The measurements were made using a magnetic storage ring. The ions in the ring were merged with a monoenergetic electron beam and neutral and positively charged fragments were detected. We cover larger energy ranges than in many of the previous experiments, and this is the first time both single and double detachment have been measured simultaneously. This allows us to present accurate ratios between the single and double detachment cross sections. On the basis of these ratio measurements we discuss possible mechanisms leading to double detachment.
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