| 1. |
- Gärling, Anita
(författare)
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Parents' perceptions of children's accident risk
- 1988
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of the present thesis was, first, to study how parents and other adults percieve or judge children’s accident risk, and, secondly, to relate such judgements to the subjects’ preferences for and satisfaction with different residential conditions.A theoretical framework is proposed which assumes that judgements of children’s accident risk are based on beliefs about what causes accidents to children. Such beliefs are furthermore assumed to be acquired more often from indirect sources than from own direct experiences. Nevertheless, because of parents’ higher motivation to protect their children, they are assumed to differ from other adults who are not parents with respect to their causal models and, as a consequence, their risk perceptions.To test some implications of the theoretical framework, three empirical studies were carried out in which parents and nonparents were requested to judge the risk children run of having accidents under different circumstances and to judge the strengths of five causes of such accidents, the parent, the child, the environment, other people, and chance. In two of the studies the subjects were also requested to express their preferences for different residential neighborhoods varying in traffic conditions, or satisfaction with their own residential conditions either as it is or if changed in different ways.Support for the implications of the theoretical framework was obtained in that causal explanations of accidents were shown to play a decisive role for judgements of accident risk. However, very slight differences were found between parents’ and nonparents’ causal models and risk perceptions. The results furthermore indicated that accident risk was of importance for parents’ satisfaction with their residential conditions if changes with perceived accident consequences were implemented. In this respect parents differed from nonparents. For the latter other things than children’s accident risk tended to be more important.
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| 2. |
- Ingemarson, Rolf, 1954-
(författare)
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Herpes simplex ribonucleotide reductase
- 1989
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In all bacterial, plant and animal cells, as well as in many viruses, genetic information resides in DNA (deoxyribonucleic acid). Replication of DNA is essential for proliferation, and DNA-containing viruses (such as herpesviruses) must carry out this process within the mammalian cells they infect. The enzyme ribonucleotide reductase catalyzes the first unique step leading to the production of the four deoxy-ribonucleotides used to make DNA. Each deoxyribonucleotide is produced by reduction of the corresponding ribonucleotide. After infection of a mammalian cell with herpes simplex virus (HSV) a new ribonucleotide reductase activity appears, which is distinct from the mammalian enzyme activity. This is due to induction of a separate, virally-encoded ribonucleotide reductase. Two monoclonal antibodies were raised against HSV (type 1) ribonucleotide reductase, and were found to bind but not neutralize its enzyme activity. One antibody recognized a larger (140 kD) protein and the other a smaller (40 kD) protein, suggesting the HSV 1 ribonucleotide reductase had a heterodimeric composition similar to that found in many other organisms. The 140 kD protein was sequentially degraded to 110 kD, 93 kD and 81 kD proteins by a host (Vero) cell-specific serine protease. Of these different proteolytic products, at least the 93 kD residue was enzymatically active, suggesting that part of the 140 kD protein may have functions unrelated to ribonucleotide reduction. The 140 and 40 kD proteins bound tightly to each other in a complex of the a2ß2 type, as shown by analytical glycerol gradient centrifugation. An assay system for functional small and large subunits of HSV 1 ribonucleotide reductase was developed, using two temperaturesensitive mutant viruses, defective in either the large (tsl207) or small (tsl222) subunits. Active holoenzyme was reconstituted both in vitro, by mixing extracts from cells infected with either mutant, and in vivo by coinfection of cells with both mutants. The gene encoding the small subunit of HSV 1 ribonucleotide reductase was cloned into an expression plasmid under control of a tac promoter. The recombinant protein was purified to homogeneity from extracts of transfected E. coli, and was active when combined with large subunit, as provided by extracts of tsl222- infected hamster (BHK) cells. The protein contained a novel tyrosyl free radical that spectroscopically resembled, but was distinguishable from, the active-site free radical found in either the E. coli or mammalian small subunits of ribonucleotide reductase. The gene encoding the large subunit of HSV 1 ribonucleotide reductase was also expressed in E. coli, using similar techniques. The recombinant large subunit was immunoprecipitated from extracts of transfected bacteria, and showed weak activity when combined with small subunit, provided by extracts of tsl20-infected hamster (BHK) cells.
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| 3. |
- Janlert, Lars-Erik, 1950-
(författare)
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Studies in knowledge representation : modeling change - the frame problem : pictures and words
- 1985
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In two studies, the author attempts to develop a general symbol theoretical approach to knowledge representation.The first study, Modeling change -the frame problem, critically examines the - so far unsuccessful - attempts to solve the notorious frame problem. By discussing and analyzing a number of related problems - the prediction problem, the revision problem, the qualification problem, and the book-keeping problem - the frame problem is distinguished as the problem of finding a representational form permitting a changing, complex world to be efficiently and adequately represented. This form, it is argued, is dictated by the metaphysics of the problem world, the fundamental form of the symbol system we humans use in rightly characterizing the world.In the second study, Pictures and words, the symbol theoretical approach is made more explicit. The subject Is the distinction between pictorial (non-linguistic, non-propositional, analogical, "direct") representation and verbal (linguistic, propositional) representation, and the further implications of this distinction. The study focuses on pictorial representation, which has received little attention compared to verbal representation. Observations, ideas, and theories in AI, cognitive psychology, and philosophy are critically examined. The general conclusion is that there is as yet no cogent and mature theory of pictorial representation that gives good support to computer applications. The philosophical symbol theory of Nelson Goodman is found to be the most thoroughly developed and most congenial with the aims and methods of AI. Goodman's theory of pictorial representation, however, in effect excludes computers from the use of pictures. In the final chapter, an attempt is made to develop Goodman's analysis of pictures further turning it into a theory useful to AI. The theory outlined builds on Goodman's concept of exemplification. The key idea is that a picture is a model of a description that has the depicted object as its standard model. One consequence Is that pictorial and verbal forms of representation are seen less as competing alternatives than as complementary forms of representation mutually supporting and depending on each other.
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