| 1. |
- Arvanitis, Leena, et al.
(författare)
-
Novel antagonistic interactions associated with plant polyploidization influence trait selection and habitat preference.
- 2010
-
Ingår i: Ecology Letters. - : Wiley. - 1461-023X .- 1461-0248. ; 13:3, s. 330-7
-
Tidskriftsartikel (refereegranskat)abstract
- Polyploidization is an important mechanism for sympatric speciation in plants. Still, we know little about whether plant polyploidization leads to insect host shifts, and if novel interactions influence habitat and trait selection in plants. We investigated herbivory by the flower bud gall-forming midge Dasineura cardaminis on tetraploids and octoploids of the herb Cardamine pratensis. Gall midges attacked only octoploid plant populations, and a transplantation experiment confirmed this preference. Attack rates were higher in populations that were shaded, highly connected or occurred along stream margins. Within populations, late-flowering individuals with many flowers were most attacked. Galling reduced seed production and significantly influenced phenotypic selection on flower number. Our results suggest that an increase in ploidy may lead to insect host shifts and that plant ploidy explains insect host use. In newly formed plant polyploids, novel interactions may alter habitat preferences and trait selection, and influence the further evolution of cytotypes.
|
|
| 2. |
- Box, Marcus
(författare)
-
New Venture, Survival, Growth : Continuance, Termination and Growth of Business Firms and Business Populations in Sweden During the 20th Century
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation focuses on the formation, growth and discontinuance of business populations and firms in Sweden during the 20th century. It addresses some key issues in the domain of economic and social sciences, and in particular entrepreneurship and small business research: if and when firms grow, stagnate and decline, as well as how long firms survive and when they are likely to disband. Previous research has primarily analyzed these questions from a short time frame. Further, an individual or firm-oriented focus is commonly assumed. In that, alternative or complementary explanations to the growth and survival of firms may be disregarded. In contrast to much previous research, this dissertation assumes a micro-to-macro, longitudinal and demographic population approach. The period of investigation is over one hundred years. In addressing the growth and survival of firms, it takes into account the impact of firm-specific structural factors (such as firm age and size), generation (cohort) effects, as well as the influence of macroeconomic, exogenous factors. Further, the relationship between managerial/ownership succession and firm performance is also addressed. Both cross-sectional and longitudinal databases are employed in the dissertation. Its main empirical material consists of unique longitudinal data on new business firms, traced at the firm level from their birth to their termination. More specifically, seven birth cohorts – generations – of approximately 2,200 firms founded in 1899, 1909, 1912, 1921, 1930, 1942 and 1950 are included. The main findings show that ownership/management succession in firms had a quite weak correlation with firm performance and survival. At least at an aggregate level, and with some exceptions, it is debatable if the loss and replacement of owner-managers in small and in larger firms have any observable effects on firm performance. Furthermore, macroeconomic phenomena influence the conditions of individual firms as well as populations/aggregates of businesses. Both the growth and termination of firms and firm populations are found to be related to real economic (environmental) conditions; e.g. favorable macroeconomic conditions implied that firms grew in size. At the same time, under certain circumstances, the influence of structural variables (firm age and size) – as suggested in much previous research – is found to be of importance. As concerns firm growth, as well as firm termination, the economic environment and structural factors interact. These findings challenges individual or firm-level research that mainly focus on personal traits and behaviors in explaining firm success and failure. Other previous assumptions are also challenged when taking a longer time perspective into consideration. For decades, organization and business research have acknowledged a liability of newness and of size for business firms. While this might be true under some conditions, this liability of newness is falsified in the study: the termination behavior of some firm generations did not correspond with these assumptions. Thus, the perspectives and methodology applied in the dissertation complement earlier approaches in entrepreneurship and small business research.
|
|
| 3. |
- Doherty, Patrick, 1957-, et al.
(författare)
-
The WITAS unmanned aerial vehicle project
- 2000
-
Ingår i: Proceedings of the 14th European Conference on Artificial Intelligence (ECAI). - Amsterdam : IOS Press. - 1586030132 - 4274903885 ; , s. 747-755
-
Konferensbidrag (refereegranskat)abstract
- The purpose of this paper is to provide a broad overview of the WITAS Unmanned Aerial Vehicle Project. The WITAS UAV project is an ambitious, long-term basic research project with the goal of developing technologies and functionalities necessary for the successful deployment of a fully autonomous UAV operating over diverse geographical terrain containing road and traffic networks. Theproject is multi-disciplinary in nature, requiring many different research competences, and covering a broad spectrum of basic research issues, many of which relate to current topics in artificial intelligence. A number of topics considered are knowledge representation issues, active vision systems and their integration with deliberative/reactive architectures, helicopter modeling and control, ground operator dialogue systems, actual physical platforms, and a number of simulation techniques.
|
|
| 4. |
- Eriksson Wiklund, Ann-Kristin, et al.
(författare)
-
Contaminants and habitat choice in the Baltic Sea: Behavioural experiments with the native species, Monoporeia affinis, and the invasive genus, Marenzelleria
- 2009
-
Ingår i: Estuarine, Coastal and Shelf Science. - : Elsevier BV. - 0272-7714 .- 1096-0015. ; 81, s. 238-246
-
Tidskriftsartikel (refereegranskat)abstract
- The invasive polychaete genus, Marenzelleria and the native amphipod, Monoporeia affinis are food and habitat competitors in the Baltic Sea. Previous studies have shown that moderate densities of Marenzelleria can affect the behaviour of M. affinis. To examine the short-term interactive effects of interspecific habitat choice and environmental contaminants a series of habitat colonisation experiments were performed. The contaminants examined included harbor sediments and sediment spiked with the antifouling substances, Cu, Zn and Irgarol. Polychaetes and amphipods were exposed to contaminants in single-species and two-species experiments. In spiked-sediment experiments, M. affinis showed clear dose-dependent response. These experiments verified that behavioural response of M. affinis to different habitats is a sensitive method for testing toxicity under controlled conditions. In experiments with three different harbor sediments and reference sediment both species showed the lowest preference for the reference sediment. This sediment also had the lowest content of quality food, indicating that factors such as food quality and quantity may override the disturbing effects of contaminants in natural sediments. The presence of Marenzelleria spp. did not affect amphipod habitat choice, indicating no short-term effects, which implies that both species can co-exist provided sufficient food is available.
|
|
| 5. |
- Fogelström, Elsa, et al.
(författare)
-
Plant-herbivore synchrony and selection on plant flowering phenology
- 2017
-
Ingår i: Ecology. - : Wiley. - 0012-9658 .- 1939-9170. ; 98:3, s. 703-711
-
Tidskriftsartikel (refereegranskat)abstract
- Temporal variation in natural selection has profound effects on the evolutionary trajectories of populations. One potential source of variation in selection is that differences in thermal reaction norms and temperature influence the relative phenology of interacting species. We manipulated the phenology of the butterfly herbivore Anthocharis cardamines relative to genetically identical populations of its host plant, Cardamine pratensis, and examined the effects on butterfly preferences and selection acting on the host plant. We found that butterflies preferred plants at an intermediate flowering stage, regardless of the timing of butterfly flight relative to flowering onset of the population. Consequently, the probability that plant genotypes differing in timing of flowering should experience a butterfly attack depended strongly on relative phenology. These results suggest that differences in spring temperature influence the direction of herbivore-mediated selection on flowering phenology, and that climatic conditions can influence natural selection also when phenotypic preferences remain constant.
|
|
| 6. |
- Granlund, Gösta H., et al.
(författare)
-
Issues in Robot Vision
- 1994
-
Ingår i: Image and Vision Computing. - : Elsevier BV. - 0262-8856 .- 1872-8138. ; 12:3, s. 131-148
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we discuss certain issues regarding robot vision. The main theme will be the importance of the choice of information representation. We will see the implications at different parts of a robot vision structure. We deal with aspects of pre-attentive versus attentive vision, control mechanisms for low level focus of attention, and representation of motion as the orientation of hyperplanes in multdimensional time-space. Issues of scale will be touched upon, and finally, a depth-from stereo algorithm based on guadrature filter phase is presented.
|
|
| 7. |
- Hassila, Carl Johan
(författare)
-
Additive Manufacturing of Ni-Fe Superalloys : Exploring the Alloying Envelope and the Impact of Process on Mechanical Properties
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Additive manufacturing of metals has received a lot of attention in the last decade as this family of manufacturing processes allows the manufacturing of complicated geometries which would be difficult to produce using conventional manufacturing techniques. Additive manufacturing of the Ni-Fe based superalloys 625 and 718 using the Powder Bed Fusion – Laser Beam (PBF-LB) process is facilitated by the fact that these alloys were developed as weldable alternatives to other high-strength, high-temperature Ni-based superalloys. However, given that these alloys were developed with casting and forging as the main manufacturing route, the alloying composition of these alloys may possibly be tuned to better suit the PBF-LB process. In this thesis, small changes to the alloy 625 and 718 alloy compositions were made, with the goal of either improving material properties or reducing the environmental footprint of the produced materials. For alloy 718, the influence of carbon content on the resulting microstructure and mechanical properties was investigated both in the as-built and heat-treated conditions using tensile and impact testing. A similar study, but also including corrosion experiments, was performed on an alloy 625 composition which had been tuned to allow it to be atomized using nitrogen instead of argon, a transition that results in environmental benefits as argon gas carries with it a larger environmental footprint compared to nitrogen gas. In addition to the above, as the process conditions in the PBF-LB process have a strong influence on the developing microstructure, their influence on rolling contact fatigue and residual stresses in printed alloys 625 and 718 were investigated. Rolling contact fatigue experiments were performed on alloy 625 and were complemented by a fractographic study which showed that the different grain structures achieved depending on the used process condition affected the pitting damage development. Meanwhile, the residual stress experiments were performed on PBF-LB processed alloy 625 and 718. The residual stresses in the materials were first calculated using experimental data attained from high energy synchrotron diffraction experiments. These results were then compared to the predicted stresses from a thermo-mechanical model. The thermomechanical model included a built-in mechanism-based material model which was shown to successfully simulate relaxation effects stemming from the cyclic heating of the material during the PBF-LB process. Lastly, a modelling approach using the thermo-mechanical model was developed which allowed the model to successfully predict the stresses also when using different scanning strategies.
|
|
| 8. |
|
|
| 9. |
- Hassila Karlsson, Carl Johan, et al.
(författare)
-
Influence of scanning strategy on residual stresses in laser powder bed fusion manufactured alloy 718: Modeling and experiments
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Residual stresses are a known phenomenon in additively manufactured materials. The residual stresses increase the risk of cracks, limit in-service performance, and distort printed parts. In this work, thermo-mechanical finite element models using the hatch-by-hatch and layer-by-layer approach, and the inherent strain method has been developed and applied to predict the effects of different scanning strategies on the deflection and the residual stresses of two PBF-LB processed geometries. To account for viscoplasticty and relaxation effects, a mechanism-based material model have been implemented and used. It is shown that the hatch-by-hatch approach and inherent strain method both successfully predicted the experimentally measured deflections of the first geometry, which was printed using different scanning directions. To predict the stress field experimentally, high-energy synchrotron measurements have been used to. The thermo-mechanical models and the inherent strain method both captures the trend of experimentally measured residual stress fields, although with an overall underprediction. The predictions of the models were evaluated, and their accuracy discussed in terms of physical aspects of the Powder Bed Fusion – Laser Beam process.
|
|
| 10. |
- Herlitz, Johan, 1949, et al.
(författare)
-
Morbidity and quality of life 5 years after early intervention with metoprolol in suspected acute myocardial infarction.
- 1988
-
Ingår i: Cardiology. - : Karger AG. - 0008-6312 .- 1421-9751. ; 75:5, s. 357-64
-
Tidskriftsartikel (refereegranskat)abstract
- In 1,395 patients in the age range 40-74 years participating in a double-blind trial with metoprolol in suspected acute myocardial infarction morbidity and quality of life were assessed during the first 5 years after randomization. During the first 3 months patients were given 200 mg metoprolol daily or placebo. Thereafter the two groups were treated similarly. Mortality during 5 years was 24.2% in patients originally randomized to metoprolol versus 25.7% in patients originally randomized to placebo (p greater than 0.2). No difference was observed regarding reinfarction rate, stroke or occurrence of bypass surgery during the 5-year follow-up. During the first 3 months 10% of patients in the metoprolol group were rehospitalized for various reasons versus 13% in the placebo group. The corresponding figures for 5 years were 59 and 60%, respectively. Among patients surviving 5 years 84% in both groups were on some medication of which beta-blockade was the dominating one. Symptoms of chest pain, dyspnea, claudicatio, smoking habits and working capacity did not differ and neither did quality of life according to the Nottingham Health Profile. We thus conclude that morbidity and quality of life were not significantly affected 5 years after early intervention with metoprolol in patients with suspected acute myocardial infarction.
|
|
