| 1. |
- Hansson, Mattias, et al.
(författare)
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Bacterial ferrochelatase turns human: Tyr13 determines the apparent metal specificity of Bacillus subtilis ferrochelatase.
- 2011
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Ingår i: Journal of Biological Inorganic Chemistry. - : Springer Science and Business Media LLC. - 1432-1327 .- 0949-8257. ; 16:2, s. 235-242
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Tidskriftsartikel (refereegranskat)abstract
- Ferrochelatase catalyzes the insertion of Fe(2+) into protoporphyrin IX. The enzymatic product heme (protoheme IX) is a well-known cofactor in a wide range of proteins. The insertion of metal ions other than Fe(2+) occurs rarely in vivo, but all ferrochelatases that have been studied can insert Zn(2+) at a good rate in vitro. Co(2+), but not Cu(2+), is known to be a good substrate of the mammalian and Saccharomyces cerevisiae ferrochelatases. In contrast, Cu(2+), but not Co(2+), has been found to be a good substrate of bacterial Bacillus subtilis ferrochelatase. It is not known how ferrochelatase discriminates between different metal ion substrates. Structural analysis of B. subtilis ferrochelatase has shown that Tyr13 is an indirect ligand of Fe(2+) and a direct ligand of a copper mesoporphyrin product. A structure-based comparison revealed that Tyr13 aligns with a Met residue in the S. cerevisiae and human ferrochelatases. Tyr13 was changed to Met in the B. subtilis enzyme by site-directed mutagenesis. Enzymatic measurements showed that the modified enzyme inserted Co(2+) at a higher rate than the wild-type B. subtilis ferrochelatase, but it had lost the ability to use Cu(2+) as a substrate. Thus, the B. subtilis Tyr13Met ferrochelatase showed the same metal specificity as that of the ferrochelatases from S. cerevisiae and human.
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| 4. |
- Cattani, F., et al.
(författare)
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Multihump soliton-like structures in interactions of lasers and Bose-Einstein condensates
- 2011
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Ingår i: Europhysics Letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 94:5, s. 53003-
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is made of multihump and periodic solutions of the semiclassical coupled equations describing laser radiation copropagating with a Bose-Einstein condensate. Solutions reminiscent of optical vector solitons have been found and have been used to gain understanding of the dynamics observed in the numerical simulations, in particular to shed light on the phenomenon of jet emission from a condensate interacting with a laser.
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| 5. |
- Doving, Kjell B., et al.
(författare)
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Visualizing a set of olfactory sensory neurons responding to a bile salt
- 2011
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Ingår i: Journal of Experimental Biology. - : The Company of Biologists. - 0022-0949 .- 1477-9145. ; 214:1, s. 80-87
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, we exposed the olfactory epithelia of crucian carp, Carassius carassius, and brown trout, Salmo trutta, to dextran coupled with Alexa dyes together with odorants. Dye uptake was severely reduced after pre-exposure to nocodazole, an inhibitor of microtubule polymerization that impairs endocytosis, supporting the hypothesis that odour-activated olfactory receptor molecules undergo endocytosis. Application of the bile acid taurolithocholate, a potent and specific odorant for fish, resulted in the labelling of a sparse (less than 3%) cell population with the typical morphology of ciliated sensory neurons (CSNs) - long dendrites and cell somata deep in the sensory epithelium. The dye was distributed throughout the sensory neuron, also revealing axons and target glomeruli. Stained axons redistribute at the entrance of the olfactory bulb and terminate in two small target areas, a dorsal and a medial one. These results are consistent with the notion that taurolithocholate is detected specifically by a few ciliated sensory neurons. Application of the olfactory epithelium of brown trout to bile acid stained cells with the appearance of CSNs. Application of an alarm agonist, hypxanthine-3-N-oxide, to crucian carp olfactory organ caused staining of another set of sensory neurons. Furthermore, our results show that odour-induced uptake of a dye can serve to identify the subtype of olfactory sensory neurons responding to a particular odorant, and to pinpoint the target regions of these neurons in the olfactory bulb as a first step to elucidating the neuronal network responding to a particular odour.
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| 6. |
- Elgan, Tobias H., et al.
(författare)
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Design of a Web-based individual coping and alcohol-intervention program (web-ICAIP) for children of parents with alcohol problems: study protocol for a randomized controlled trial
- 2012
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Ingår i: BMC Public Health. - : Springer Science and Business Media LLC. - 1471-2458. ; 12
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Tidskriftsartikel (refereegranskat)abstract
- Background: It has been estimated that approximately 20% of all Swedish children grow up with parents having alcohol problems, which may result in negative outcomes among these children. Therefore, most Swedish municipalities provide resources for support, but at the same time figures reveal that not even 2% receive support, mainly due to difficulties in identifying and recruiting these children into support programs. Delivering intervention programs to children and adolescents via the Internet seems a promising strategy, but to date, the number of web-based interventions aimed at this target group is very scarce. We have therefore developed a novel internet-delivered therapist assisted self-management intervention called the web-ICAIP (Individual Coping and Alcohol Intervention Program) for adolescents having parents with alcohol problems. The purpose of the program is to strengthen adolescents' coping behavior, improve their mental health, and postponing the onset or decreasing risky alcohol consumption. This paper describes the web-ICAIP and the design of a randomized controlled trial (RCT) to measure the efficacy of this intervention. Methods/Design: The RCT will include at least 183 adolescents (15-19 year old) who will be randomly allocated to two conditions where one group has access to the web-ICAIP and the other is a waiting list control group. Participants will be recruited from websites containing information and facts for adolescents about alcohol and other drugs. Possible participants will be screened using the short version of the Children of Alcoholics Screening Test (CAST-6). The assessment consists of a baseline and two follow-up measurements taking place after two and six months, respectively. The primary outcomes include the Center for Epidemiological Studies Depression Scale (CES-DC), a coping behavior scale, and also the short version of the Alcohol Use Disorders Identification Test (AUDIT-C). Additional outcomes include the "Ladder of life" which measures overall life satisfaction and questions concerning program adherence. Discussion: There is an urgent need for developing and evaluating web-based intervention programs which target children having parents with alcohol problems. This study will therefore make an important contribution to this novel field of research.
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| 7. |
- Gasch, Tobias, et al.
(författare)
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Concrete Support Structure for Hydroelectric Generators Subjected to Rotor Dynamic Loads
- 2014
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Ingår i: International Symposium on Dams in a Global Enviromental Challange. - Bali.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In earlier times, the generators of the hydropower plants ran more or less continuously, while nowadays there are many planned starts and stops. The hydropower stations are thereby, due to the new pattern of operation, subjected to loads that they were not originally designed for. The aim of this study is to understand the complex interaction between the power generating system and the supporting concrete structure, during this new operational pattern.During inspections, cracks were discovered in the concrete structure of the power house, near the stator and rotor spider supports, at several hydropower stations in Sweden. In a previous phase of this project it was shown that these cracks initiated due to the combined effect of drying shrinkage, mechanical loads and variations in temperature due to starts and stops. Cracking of the concrete structure reduces its stiffness, which may result in larger loads acting on the structure and vibrations exceeding the unit’s strict tolerance limits.In this part of the study, the behaviour of a concrete support structure subjected to rotor dynamic loads during normal operation has been studied. A detailed 3D numerical model has been developed which include hydropower unit. The results of this study show that a reduced structural stiffness of the concrete support structure, due to cracking, influences the behaviour of the rotating system.
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| 8. |
- Gasch, Tobias, et al.
(författare)
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Cracking in the concrete foundation for hydropower generators : Part II
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- An extensive program for improvement of the hydropower plants in Sweden is currently on-going. The aims are to secure future production and to maintain and further develop an already high dam safety.During inspection, cracks were discovered in the concrete foundation, near the stator and rotor spider supports, at some hydropower stations in Sweden. The cracks were believed to be related to new patterns for generator operation, thereby changing the dynamic loading of the stator and rotor spider supports. Previously the generators ran continuously, while nowadays there are an increased number of stops and starts, sometimes even several times during one day. Increased dynamic forces due to runaways, and also other dynamic events such as emergency stops, may also contribute to increased stress levels and cracking of the foundation. Furthermore, although extreme loads such as short circuits of the generator seldom occurs, the influence on the dynamic forces acting on the supporting structure and concrete foundation may be strongly influenced during such events.The objective of this study is to understand the complex interaction between the power generating system (stator, rotor, turbine, etc.) and its supporting concrete structure. It is important from a dam safety perspective to determine the causes of existing structural cracks in the foundation. Furthermore, to be able to predict further crack propagation of the concrete foundation will help to determine future maintenance requirements.A three dimensional non-linear finite element model developed earlier was used to evaluate a methodology for analyses of the interaction between the generator and the concrete foundation. The influence of cracks in the concrete foundation was investigated by including the fracture pattern obtained in earlier FE analyses of time-dependent thermal and moisture gradients. These analyses showed that the drying shrinkage induced cracking inside the concrete foundation and especially close to the supports of the stator and the rotor spider. The obtained fracture pattern for the previous analysis was used as input for this study, with the concrete foundation’s changed structural properties and their influence on the interaction with the generator considered in the analyses. Furthermore, deadweight and operational load were also included in the analyses.The study show that FE models with a cracked concrete foundation can be used to analyse structural interaction betwee foundation and generator components during operation of a hydro power generator. The crack pattern can be determined by FE analyses, or by in-situ measurements of existing concrete cracks for a specific concrete foundation. The analyses show that further studies are needed regarding the combined effects from thermo-mechanical loads, drying shrinkage, creep and dynamical loads caused by the generator. The combined effects may further increase the stress levels for the concrete foundation, especially locally near perforations, and stator and rotor spider supports. These analyses should be performed with an increased numerical resolution for both the concrete foundation and the supporting structure for the generator, with an increased accuracy for the local stress variations near perforations of the foundation and also at the supports for the generator. This research area will be further investigated within a recently started research project at KTH, financed by the Swedish Hydropower Centre.
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| 9. |
- Hansson, Anders, 1953-, et al.
(författare)
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Working together--primary care doctors' and nurses' attitudes to collaboration.
- 2010
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Ingår i: Scandinavian journal of public health. - : SAGE Publications. - 1651-1905 .- 1403-4948. ; 38:1, s. 78-85
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Tidskriftsartikel (refereegranskat)abstract
- Multidisciplinary teamwork is recommended for various disorders and it has been suggested that it is a way to meet the new challenges and demands facing general practitioners (GPs) in modern society. Attempts to introduce the method in primary care have failed partly due to GPs' unwillingness to participate. The aim of this study was to measure attitudes towards collaboration among GPs and district nurses (DN) and to investigate whether there is a correlation between a positive attitude toward collaboration and high self-esteem in the professional role.
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| 10. |
- Hansson, Tobias, 1983, et al.
(författare)
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Bichromatically pumped microresonator frequency combs
- 2014
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Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 2469-9926 .- 2469-9934. ; 90:1
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Tidskriftsartikel (refereegranskat)abstract
- A study is made of the nonlinear dynamics of bichromatically pumped microresonator Kerr frequency combs described by a driven and damped nonlinear Schrodinger equation, with an additional degree of freedom in the form of the modulation frequency. A truncated four-wave model is derived for the pump modes and the dominant sideband pair, which is found to be able to describe much of the essential dynamical behavior of the full equation. The stability of stationary states within the four-wave model is investigated, and numerical simulations are made to demonstrate that a large range of solutions, including cavity solitons, are possible beyond previously considered low-intensity patterns.
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