| 1. |
- Gerén, Linda, 1962-
(författare)
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Pionic Fusion Study of the 6He Halo
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The structure of the halo nucleus 6He has been investigated in a pionic fusion experiment at the CELSIUS storage ring facility in Uppsala. The 4He(d, 6He)π+ reaction was studied 0.6 - 5.0 MeV above threshold in the centre-of-mass frame with a deuteron beam incident on a 4He gas target. The 6He ions were detected in a ΔE - E solid-state detector telescope inserted into the CELSIUS ring. The results for the total and differential cross section are presented and compared to results for the analogue reaction producing the 3.56 MeV analogue state in 6Li. A simple model of the reaction gives results consistent with earlier findings of 6He as having a spatial extent considerably exceeding that of the alpha particle. It is also shown that information about the high momentum part of the halo wave function can be extracted from the results of this pionic fusion measurement.
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| 2. |
- Isaksson, Lennart
(författare)
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High-resolution measurement of the ¹⁶O(γ,pn) reaction
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The 16O(gamma,pn) reaction has been measured with a resolution high enough to resolve individual low-lying states in the residual 14N nucleus. The relative population of the states provides detailed information about the quantum numbers of the proton-neutron pairs on which photons are absorbed. Partial cross-sections, available to the acceptance of the detector system, have been extracted for the individual states, and compared to a recent calculation based on absorption on one-pion exchange currents and the Delta-resonance current. The experiment was performed at the Maxlab accelerator laboratory in Lund, Sweden, using tagged photons at an energy of 67-76 MeV. The proton detector angular range was 60-100 degrees and the corresponding number for the neutron detector was 81-103 degrees. A missing-energy resolution of 1.5 MeV was obtained. The relative population of the states in the residual 14N nucleus indicates that the (gamma,pn) reaction takes place predominantly on proton-neutron pairs coupled to (J^pi,T) = (1^+,0), where J is the total angular momentum of the pair, pi is the parity and T is the isospin. The cross-section for absorption on (0^+,1) pairs is strongly suppressed. Furthermore, the relative population of the states indicates that both L=0 and L=2 pairs participate in the reaction, where L is the angular momentum of the center-of-mass of the pair.
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| 3. |
- Isaksson, Lennart
(författare)
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Seamless Communications
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolution of today’s wireless technologies and small hand-held devices has enabled the handling of the trade-off between mobility and performance. Things have, however, become more complex. Users demand high performance when using small and resource-efficient devices. Users also demand high-performance connectivity anywhere and anytime without having to care about transitions between different access networks. As of today, the absence of Mobile IP (MIP) support in most networks implies the need for a reconnection of the service as soon as the access network changes. That is why a new seamless communication concept is required. In the thesis, a new seamless communication concept is proposed. The goal is to be Always Best Connected (ABC) even if the conditions change. Initially, a network link has to be selected and a connection has to be established. The service used should be maintained as long as the conditions are fulfilled. First, a set of Generic Services (GSs), each related to a specific communication task, is defined. Furthermore, a deep performance investigation of some of the wireless technologies available is summarized and used. Based on the combination of a GS and a wireless technology selected criteria are used. The data extracted from our measurements have the option of later being fed into statistical algorithms. The translation of the extracted information through the statistical methods could be non-linear and for that reason the Fuzzy Set Theory (FST) is used. The FST provides us with the tool needed for the next step, the decision aiming at ABC. To be able to handle the large amount of data, the Multi-Criteria Decision Making (MCDM) is used. This decision model requires a linguistic 9-point scale which suits the FST tool perfectly. A judgment between different criteria can then be made. Moreover, the thesis describes a couple of important issues regarding the Internet protocol address problem. Each problem is discussed and solutions are presented in the context of having seamless communication without today’s constraints. The result is a seamless communication concept that is more flexible than other solutions. Both the FST and the MCDM tools have been successfully implemented into a running prototype.
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| 4. |
- Isaksson, Mikael, 1974-
(författare)
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On the quantitative analysis of electronic energy transfer/migration in proteins studied by fluorescence spectroscopy
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Two recently developed theories of electronic energy transfer/migration were for the first time applied to real protein systems for extracting molecular distances. The partial donor-donor energy migration (PDDEM) is an extension to the previously developed donor-donor energy migration (DDEM, F Bergström et al PNAS 96, 1999, 12477) which allows using chemically identical but photophysically different fluorophores in energy migration experiments. A method based on fluorescence quenching was investigated and applied to create an asymmetric energy migration between fluorophores which were covalently and specifically attached to plasminogen activator inhibitor type 2 (PAI-2). It was also shown experimentally that distance information can be obtained if the fluorescence relaxation for photophysically identical donors, exhibits multi-exponential relaxation. An extended Förster theory (EFT) that was previously derived (L. B.-Å. Johansson et al J. Chem. Phys., 1996, 105) ha been developed for analysis of donor-acceptor energy transfer systems as well as DDEM systems. Recently the EFT was also applied to determine intra molecular distances in the protein plasminogen activator inhibitor type 1 (PAI-1) which was labelled with a sulfhydryl specific derivative of BODIPY. The EFT explicitly accounts for the time-dependent reorientations which in a complex manner influence the rate of electronic energy transfer/migration. This difficulty is related to the “k2-problem”, which has been solved. It is also shown experimentally that the time-correlated single-photon counting (TCSPC) data is sensitive to the mutual configuration between the interacting fluorophores. To increase the accuracy in the extracted parameters it is furthermore suggested to collect the fluorescence data under various physico-chemical conditions. It was also shown that the Förster theory is only valid in the initial part of the fluorescence decay.
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| 5. |
- Lindqvist, Maria, 1983-
(författare)
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Epidemiological and molecular biological studies of multi-resistant methicillin-susceptible Staphylococcus aureus
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Antibiotic resistance is increasingly recognised as a major problem and threat. During the last decades Gram-positive bacteria in general, and methicillin-resistant Staphylococcus aureus (MRSA) in particular, have been in focus both concerning matters of antibiotic resistance and as pathogens causing health care-associated (nosocomial) infections. In contrast to MRSA, studies on clonal distribution of methicillin-susceptible S. aureus (MSSA) are scarce. However, interest in MSSA has increased since it was shown that MRSA emerges from susceptible backgrounds by acquisition of a staphylococcal cassette chromosome element, carrying the mecA gene encoding methicillin-resistance (SCCmec).In an outbreak investigation of MRSA in Östergötland County, Sweden, in 2005, a high incidence of MSSA isolates with concomitant resistance to erythromycin, clindamycin and tobramycin (ECT-R) was detected. Analysis showed that 91 % of the investigated isolates were genetically related (clonal). The ECT-R clone was divided into four different but closely related patterns with pulsed-field gel electrophoresis (PFGE), and was designated spa type t002. Whole genome sequencing revealed that the ECT-R clone carried a pseudo-SCC element estimated to be 12 kb in size, showing a resemblance of more than 99 % with the SCCmec type II element of MRSA strain N315 (New York/Japan clone). This suggested a probable derivation from a highly successful MRSA strain, which had partially excised its SCCmec. The clonal outbreak was concentrated in eight hospital departments and two primary care centres, all located in the city of Linköping. Despite a high exchange of patients with the hospitals in the neighbouring counties in southeast Sweden (Jönköping- and Kalmar County), the ECT-R clone seemed to be limited to Östergötland County. However, a tobramycin-resistant clone predominated by isolates of spa type t084 was found in all three counties in southeast Sweden, and in particular among newborns, suggesting inter-hospital transmission.The ECT-R clone has survived as an abundant MSSA clone for a decade in Östergötland County, which indicates an insufficiency in the maintenance of basic hygiene guidelines, and that the clone probably possesses mechanisms of virulence and transmission that are yet to be discovered.
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