| 1. |
- Strömberg, Dan, 1959, et al.
(author)
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Relativistic calculations on some mercury sulphide molecules
- 1991
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In: Water Air and Soil Poll. - 0049-6979. ; 56:1, s. 681-695
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Journal article (peer-reviewed)abstract
- Relativistic quantum calculations at the CASSCF- and CCI-levels were performed on the Hg(SH)2, HgSH and HgS molecules. The relativistic effects were taken into account by a relativistic effective core potential method. Dissociation energies and optimal geometries were calculated for these three molecules, which are plausible atmospheric Hg compounds. The Hg(SH)2 and HgSH molecules (in the gaseous phase) have never been studied before, neither experimentally nor theoretically, i.e. the existence of these molecules are uncertain. The theoretical dissociation energies, De's, of Hg(SH)2 and HgSH (at the CCI-level) were 59 kcal·mol–1 and 3 kcal·mol–1, respectively, indicating that Hg(SH)2 could be stable in the atmosphere but probably not HgSH. The theoretical De of HgS differs very much from the experimental one, but the reason for this is not clear. The Hg-S distances for Hg(SH)2, HgSH and HgS were found to be 2.38, 2.63 and 2.30 Å, respectively. The Hg-S-H angle in Hg(SH)2 was optimized to 93°. The excitation energies of Hg(SH)2, Hg(SH)2(H2O)4 and (HSHg)2S were calculated in order to see whether these species can absorb photons with wavelengths longer than 290 nm (the sunlight limit) and subsequently be photolyzed. The Hg(SH)2(H2O)4 complex is intended as a model for Hg(SH)2(aq). Photoreduction of Hg-sulfide species in sea water, yielding Hg0, could be an important source of Hg in the atmosphere. Excitation energies lower than the sunlight limit (4.3 eV290 nm) were found for Hg(SH)2 and Hg(SH)2(H2O)4, although the lowest spin and dipole allowed excitations probably lie slightly (0.2 to 0.3 eV) above this limit. Therefore a photodecomposition of Hg(SH)2(g) and Hg(SH)2(aq) by sunlight seems likely to occur.
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| 2. |
- Albin, Maria, et al.
(author)
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Retention patterns of asbestos fibres in lung tissue among asbestos cement workers
- 1994
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In: Occupational and Environmental Medicine. - 1470-7926. ; 51:3, s. 205-211
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Journal article (peer-reviewed)abstract
- Retention patterns in lung tissue (determined by transmission electron microscopy and energy dispersive spectrometry) of chrysotile, tremolite, and crocidolite fibres were analysed in 69 dead asbestos cement workers and 96 referents. There was an accumulation of tremolite with time of employment. Among workers who died within three years of the end of exposure, the 13 with high tremolite concentrations had a significantly longer duration of exposure than seven in a low to intermediate category (medians 32 v 20 years; p = 0.018, one sided). Crocidolite showed similar patterns of accumulation. In workers who died more than three years after the end of exposure, there were no correlations between concentrations of amphibole fibres and time between the end of exposure and death. Chrysotile concentrations among workers who died shortly after the end of exposure were higher than among the referents (median difference in concentrations 13 million fibres (f)/g dry weight; p = 0.033, one sided). No quantitative differences in exposure (duration or intensity) could be shown between workers with high and low to intermediate concentrations. Interestingly, all seven workers who had had a high intensity at the end of exposure (> 2.5 f/ml), had low to intermediate chrysotile concentrations at death, whereas those with low exposure were evenly distributed (31 subjects in both concentration categories); hence, there was a dependence between last intensity of exposure and chrysotile concentration (p = 0.014). Among 14 workers with a high average intensity of exposure, both those (n = 5) with high tissue concentrations of chrysotile and those (n = 10) with high tissue concentrations of tremolite fibres had more pronounced fibrosis than those with low to intermediate concentrations (median fibrosis grades for chrysotile: 2 v 1, p = 0.021; for tremolite: 2 v 0.5, p = 0.012). Additionally, workers who died shortly after the end of exposure with high concentrations of chrysotile and crocidolite had smoked more than those with low intermediate concentrations (medians for chrysotile 35 v 15 pack-years, p = 0.030; for crocidolite 37 v 15 pack-years, p = 0.012). The present data indicate that chrysotile has a relatively rapid turnover in human lungs, whereas the amphiboles, tremolite and crocidolite, have a slower turnover. Further, chrysotile retention may be dependent on dose rate. Chrysotile and crocidolite deposition and retention may be increased by tobacco smoking; chrysotile and tremolite by fibrosis.
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| 3. |
- Lidberg, Ulf, 1962, et al.
(author)
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Genomic organization, sequence analysis, and chromosomal localization of the human carboxyl ester lipase (CEL) gene and a CEL-like (CELL) gene.
- 1992
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In: Genomics. - 0888-7543. ; 13:3, s. 630-40
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Journal article (peer-reviewed)abstract
- The gene encoding human carboxyl ester lipase (CEL), including 1628 bp of the 5'-flanking region, has been isolated and characterized from two overlapping lambda phage clones. The gene spans 9832 bp and contains 11 exons interrupted by 10 introns. The exons range in size from 88 to 204 bp, except for the last exon, which is 841 bp. A major and a minor transcription initiation site were determined 13 and 7 bp, respectively, upstream of the initiator methionine. The nucleotide sequence is identical with that of the previously reported cDNA, except for the third nucleotide in the 5'-untranslated sequence, a C, which in the cDNA is a T. A TAAATA sequence is present 26 nt upstream from the major CAP site, and within the 5'-flanking region there are several putative transcription factor binding sites. Seven Alu repetitive sequence elements are present in the region analyzed. The organization of the human CEL gene is similar to that of the recently reported rat pancreatic cholesterol esterase gene. The CEL gene was assigned to chromosome 9q34-qter, which confirms the recently reported results of Tayler et al. (1991, Genomics 10: 425-431). A previously unknown gene with a striking homology to the human CEL gene, here called the CEL-like gene (CELL), has also been isolated and characterized, including 1724 bp of the 5'-flanking region. The CELL gene, which most likely is a psuedogene, spans 4846 bp, and due to the absence of a 4.8-kb segment, the CEL gene exons 2-7 are not present in the CELL gene. Despite these differences, the CELL gene is transcribed. We have also assigned the CELL gene to a separate locus at chromosome 9q34-qter.
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| 4. |
- Ohlsson, Kerstina, et al.
(author)
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Disorders of the neck and upper limbs in women in the fish processing industry
- 1994
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In: Occupational and Environmental Medicine. - 1470-7926. ; 51:12, s. 826-832
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Journal article (peer-reviewed)abstract
- OBJECTIVE--The aim was to study the association between personal factors and physical and psychosocial work environment factors and disorders of the neck or upper limbs among women in the fish processing industry. METHODS--A cross sectional study was performed on 206 women in the fish processing industry and 208 control women. Several physical and psychosocial work environment factors were evaluated. Subjective complaints about the neck or upper limbs were assessed by questionnaire and by a clinical examination. RESULTS--The study showed a high prevalence (35%) of diagnoses in the neck or shoulders of the exposed women. All prevalence odds ratios (POR's) were substantially higher in young women. There was a pronounced dose-response relation between disorders of the neck or shoulders and duration of employment for women < 45 years old. When studying 322 former workers, the proportion who claimed musculoskeletal complaints as the reason for leaving was highest among the older women. Muscular tension, stress or worry, work strain, and the largest fraction of the work time spent with highly repetitive work tasks were clearly associated with disorders of the neck or shoulders. The measurements of the wrist movements also showed that the work was performed almost without any pauses and that the median flexion and extension velocity was high (41 degree/s). The results of observation showed good agreement with the measurements of wrist motion. CONCLUSION--Work in the fish processing industry is a risk factor for disorders of the neck and upper limbs. Due to the homogenity of the physical work load in the exposed group, we could not show any associations between the objective measurements and disorders. In cross sectional studies the risk may be underestimated due to a healthy worker effect.
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| 5. |
- Strömberg, Dan, 1959, et al.
(author)
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First-order relativistic calculations on Au2 and Hg22+
- 1990
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In: Chem Phys Lett. - 0009-2614. ; 169:1-2, s. 109-115
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Journal article (peer-reviewed)abstract
- Spin-free first-order relativistic calculations have been carried out on Au, Hg at the SCF level and on Au2 and Hg22+ at the CI level using the size-consistent CPF procedure. The atomic SCF results agree with previous relativistic atomic calculations using the Cowan-Griffin procedure to within 0.5 eV. The spectroscopic constants calculated for Au2 agree fairly well with experiment and with previously published relativistic effective core potential results. For Hg22+ we obtain, in contrast to previous theoretical results, a relativistic destabilization of the binding energy. Article Outline
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| 6. |
- Strömberg, Dan, 1959, et al.
(author)
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Theoretical calculations on the structure of the hexahydrated divalent zinc
- 1990
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In: Chem Phys Lett. - 0009-2614. ; 172:1, s. 49-54
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Journal article (peer-reviewed)abstract
- SCF calculations have been performed on the title compounds in order to study the possible reasons for the anomalously large spread in the mean Hg---O bond distance previously obtained for hydrate mercury (II) ions in solution. An energy minimum is found for all three complexes, [M(H2O)6]2+, M = Zn, Cd or Hg, for a regular Th ground-state nuclear configuration. The larger spread of the Hg---O distances can be explained in terms of a weak second-order Jahn—Teller effect. An enhanced vibronic coupling leads in the mercury case to larger vibrational amplitudes of the coupling mode without invoking a static distortion. The longer mean Hg---O distance found for the hydrated mercury (II) ion in solution than in a solid hexahydrate can be explained by assuming a larger asymmetry in the distribution of the Hg---O bonds. Calculations on the [Hg(H2S)6]2+ complex also show an energy minimum for the Th configuration, although in this case the adiabatic potential surface is very flat, and more refined methods of calculation could yield a distored ground-state configuration.
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| 7. |
- Strömberg, Jan-Erik, et al.
(author)
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Bond Graph Supported Estimation of Discretely Changing Parameters
- 1993
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In: International Conference on Bond Graph Modeling, 1993. - 9781565550193 - 1565550196 ; , s. 47-52
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Conference paper (other academic/artistic)abstract
- A key factor in parameter estimation is the selection of model structure within which the fit to observed data is to be achieved. For linear systems, bond graphs have proven to give excellent support in this respect. However, for systems undergoing abrupt transitions between different (linear) modes of behaviour, the situation is far more complex. To handle this, we exploit the features of the ideal switching element as introduced by Strömberg, Top and Söderman. This solves the question of physical modelling as well as how to derive the supporting information. The approach is demonstrated on a non-trivial example using a multiple Kalman filter estimator.
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| 8. |
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| 9. |
- Strömberg, Jan-Erik, et al.
(author)
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Combining Qualitative and Quantitative Knowledge to Generate Models of Physical Systems
- 1991
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In: Proceedings of the 12th International Joint Conference on Artificial Intelligence. - Linköping : Linköping University. ; , s. 1158-1163
-
Conference paper (peer-reviewed)abstract
- All major approaches to Qualitative Reasoning rely on the existence of a model of the physical system. However, the task of finding a model is usually far from trivial. Within the area of electrical engineering, model building methods have been developed to automatically deduce models from measurements. In this paper we explicitly show how to incorporate qualitative knowledge in order to apply these methods to situations where they do not behave satisfactorily. A program has been developed and applied to a non-trivial example. The qualitative input, in terms of an incomplete bond graph, and the resulting output can be used to form a more complete bond graph. This more informative model is suitable for further reasoning.
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| 10. |
- Strömberg, Jan-Erik, et al.
(author)
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Conceptual Modelling of Hybrid Systems
- 1994
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In: Proceedings of the 1994 European Simulation and Modelling Conference. - Linköping : Linköping University. ; , s. 1095-1099
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Reports (other academic/artistic)
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| 11. |
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| 12. |
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| 13. |
- Strömberg, Jan-Erik, et al.
(author)
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Variable Causality in Bond Graphs Caused by Discrete Effects
- 1993
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In: International Conference on Bond Graph Modeling, 1993. - 9781565550193 - 1565550196 ; , s. 115-119
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Conference paper (other academic/artistic)abstract
- Current approaches to the problem of switching between modes in continuous dynamic system models tend to confound modelling and computation. Here we introduce an alternative approach ensuring a clear distinction between the physical and computational levels. Our method is centered around the idea that the variability of causal directions should be accepted rather than being alleviated. Hence, we define an ideal bond graph switching element, to deal with this variability in a bond graph uniform and systematic way. We hereby maintain the abstraction level of the bond graph language as well as the possibility to perform initial model validation directly in the graph.
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| 14. |
- Strömberg, Jan-Erik, et al.
(author)
-
Variable Causality in Bond Graphs Caused by Discrete Effects
- 1992
-
Reports (other academic/artistic)abstract
- Current approaches to the problem of switching between modes in continuous dynamic system models tend to confound modelling and computation. Here we introduce an alternative approach ensuring a clear distinction between the physical and computational levels. Our method is centered around the idea that the variability of causal directions should be accepted rather than being alleviated. Hence, we define an ideal bond graph switching element, to deal with this variability in a bond graph uniform and systematic way. We hereby maintain the abstraction level of the bond graph language as well as the possibility to perform initial model validation directly in the graph.
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| 15. |
- Söderman, Ulf, et al.
(author)
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Modelling Physical Systems with Changing Structure
- 1992
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Reports (other academic/artistic)abstract
- Causality plays an important role in essentially any aspect of reasoning about physical systems. However, causal directedness is problematic when the physical structure, i.e. the interaction between subsystems changes. This is due to the fact that causality is a global property. This problem can in principle be solved by specifying acausal models and to derive causality afterwards for the complete model. This is possible because physical systems are connected through bilateral signal flows, with no a priori fixed direction. So far, there has been no systematic and efficient way to represent acausal models of structures that undergo change. This would be an important feature of automated modelling and reasoning systems. In this paper we propose the definition of an ideal, generic switching element solving exactly this representation problem. The definition also adds a new ontological primitive to the bond graph language, though the general definition is not restricted to any specific modelling approach. Furthermore, the clear and explicit bond graph method to derive the overall causality ca be reused unaltered. Several examples are presented to illustrate our approach.
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| 16. |
- Söderman, Ulf, et al.
(author)
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The Conceptual Side of Mode Switching
- 1993
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In: Proceedings of the 1993 IEEE International Conference on Systems, Man and Cybernetics. - Linköping : Linköping University. - 0780309111 ; , s. 245-250 vol.1
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Reports (other academic/artistic)abstract
- For continuous dynamic systems there are many powerful methods for modelling. However, when dealing with systems undergoing abrupt behavioural changes, i.e. mode switching systems, the picture suddenly is changed. We here claim that the reason for this is that mode switching traditionally is treated by mathematical and/or logical solutions only. That is, at the wrong level of abstraction. We present several arguments supporting this view, and finally present our solution to this problem: the ideal switch concept.
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