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Träfflista för sökning "WFRF:(Isaksson Lennart) srt2:(2000-2004)"

Sökning: WFRF:(Isaksson Lennart) > (2000-2004)

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1.
  • Akkurt, I, et al. (författare)
  • Photoneutron yields from tungsten in the energy range of the giant dipole resonance
  • 2003
  • Ingår i: Physics in Medicine and Biology. - : IOP Publishing. - 1361-6560 .- 0031-9155. ; 48:20, s. 3345-3352
  • Tidskriftsartikel (refereegranskat)abstract
    • Photoneutron production on the nuclei of high-Z components of medical accelerator heads can lead to a significant secondary dose during a course of bremsstrahlung radiotherapy, However, a quantitative evaluation of secondary neutron dose requires improved data on the photoreaction yields. These have been measured as a function of photon energy, neutron energy and neutron angle for W-nat, using tagged photons at the MAX-Lab photonuclear facility in Sweden. This work presents neutron yields for W-nat(gamma, n) and compares these with the predictions of the Monte Carlo code MCNP-GN, developed specifically to simulate photoneutron production at medical accelerators.
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3.
  • Fiedler, Markus, et al. (författare)
  • Communication requirements of generic services for Intelligent Transport Systems
  • 2004
  • Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
    • In order to meet their users’ expectations and to be of efficient help for people using or maintaining Intelligent Transport Systems (ITS), related services need efficient support from the underlying communication systems, which in turn requires profound knowledge of those needs. This paper presents an approach to gather services into generic groups and a framework to classify their needs in terms of availability, performance, security and cost in a generic manner. These needs are consequently seen from the user’s perspective, but formulated in a way such that the matching towards technical parameters as e.g. throughput offered by a communication network can be performed. Upon comparing needs with offers, the feasibility of a certain communication technology for a certain type of service can be determined, which in turn helps to choose the right kind of connectivity in order to yield the desired degree of availability, performance, security and cost. This work is carried out within the VINNOVA-sponsored project PIITSA (Personal Information for Intelligent Transport Systems through Seamless communications and Autonomous decisions) conducted by Aerotech Telub, Blekinge Tekniska Högskola, Statens Provningsanstalt Borås and Vägverket, respectively.
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4.
  • Håkansson, Pär, et al. (författare)
  • Extended Förster theory for determining intraprotein distances : 1. The K2-dynamics and fluorophore reorientation
  • 2004
  • Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:44, s. 17243-17250
  • Tidskriftsartikel (refereegranskat)abstract
    • A detailed analysis of the previously developed (J. Chem. Phys. 1996, 105, 10896) extended Förster theory (EFT) is presented for analyzing electronic energy migration within pairs of donors (D). Synthetic data that mimics experimental time-correlated single photon counting data were generated and re-analyzed. To cover a wide dynamic range and various orientational restrictions, the rates of reorientation, as well as the orientational configurations of the interacting D-groups were varied. In general DD distances are recovered within an error limit of 5%, while the errors in orientational configurations are usually larger. The Maier−Saupe and cone potentials were used to generate an immense variety of orientational trajectories. The results obtained exhibit no significant dependence on the choice of potential function used for generating EFT data. Present work demonstrates how to overcome the classical “κ2-problem” and the frequently applied approximation of κ2 = 2/3 in the data analyses. This study also outlines the procedure for analyzing fluorescence depolarization data obtained for proteins, which are specifically labeled with D-groups. The EFT presented here brings the analyses of DDEM data to the same level of molecular detail as in ESR- and NMR-spectroscopy.
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5.
  • Hällgren, Anita, 1963-, et al. (författare)
  • Genetic relatedness among Enterococcus faecalis with transposon-mediated high-level gentamicin resistance in Swedish intensive care units
  • 2003
  • Ingår i: Journal of Antimicrobial Chemotherapy. - : Oxford University Press (OUP). - 0305-7453 .- 1460-2091. ; 52:2, s. 162-167
  • Tidskriftsartikel (refereegranskat)abstract
    • We studied 45 isolates of Enterococcus faecalis with high-level gentamicin resistance (HLGR), all but one concomitantly resistant to ciprofloxacin, and 25 ciprofloxacin-resistant isolates without HLGR for genetic relatedness using pulsed-field gel electrophoresis (PFGE). E. faecalis were isolated from patients admitted to intensive care units at eight hospitals in southern Sweden from December 1996 through December 1998. Genomic analysis by PFGE resulted in three clusters of genetically related isolates (designated clusters I, II and III) and 23 unique clones. Cluster I was found predominantly in the eastern and central parts of southern Sweden and clusters II and III in south-western Sweden. Among the 45 isolates with HLGR, 69% belonged to cluster I, 20% to cluster II, and 11% had unique PFGE patterns, which suggests that the majority of isolates with HLGR are closely related. Among the 25 ciprofloxacin-resistant isolates without HLGR, 68% had unique PFGE patterns, 12% belonged to cluster I and 20% to cluster III, which suggests the ciprofloxacin-resistant isolates are not related. All isolates with HLGR contained the aac(6′)Ie-aph(2″)Ia gene, which was carried on a Tn5281-like transposon in all isolates except one. We conclude that HLGR in E. faecalis was mainly due to dissemination of genetically related clones during the time studied, and that HLGR in these isolates was due to the presence of the aac(6′)Ie-aph(2″)Ia gene.
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7.
  • Isaksson, Lennart (författare)
  • Improved Performance of Bluetooth with Focus on Ad-Hoc Applications
  • 2004
  • Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The number of devices making use of Bluetooth cable-replacement technology has rapidly increased in numbers thanks to the amount of implementations in cellular telephones, Personal Digital Assistants (PDAs), etc. Instead of the point-to-point technique used today the wireless community demands more sophisticated solutions to transmit information between two devices, e.g. using a chat program within an ad-hoc network. However, Bluetooth provides neither a routing protocol, nor is the slave/slave bridge, which is an important enabler for point-to-multipoint communication in so-called scatternets, implemented in hardware. Another issue relates to the time-to-connect which determines the usability of Bluetooth in scenarios where the units move around. In order to build research on these topics on trustworthy ground, we first address the validation of a Bluetooth simulation model, implementing the Frequency Hopping Spread Spectrum (FHSS) technique of Bluetooth version 1.1 in a correct way. A potential source of problems in reference simulation models has been identified and corrections are described. Next, an improvement is presented for the pseudo random hop sequence regarding the distribution of frequencies used in the Adapted Channel Hopping (ACH) scheme for Bluetooth version 1.2. Further, the impact of the random backoff boundary, which determines the duration of the inquiry procedure and thus of the time-to-connect, is studied by simulation. Obviously, the settings of this parameter contained in the specification leads to suboptimal behaviour. In this thesis, a lower random backoff boundary parameter is suggested, which yields much faster time-to-connect. Finally, the Modified Reverse Path Forwarding (MRPF) routing algorithm for Bluetooth is proposed. This algorithm reduces the amount of connections needed to transmit Asynchronous Connection Less (ACL) data packets as compared to the standard RPF, at the cost of additional overhead. Altogether, especially with the proposed improvements of Bluetooth performance, this technology can be considered to be well suited for nomadic scenarios.
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8.
  • Isaksson, Lennart, et al. (författare)
  • On-Demand Ad Hoc Routing with Modified Reverse Path Forwarding for Bluetooth
  • 2004
  • Konferensbidrag (refereegranskat)abstract
    • In an ad hoc network connection establishment is done to secure a path for routing packets from source to destination. This path is then maintained to secure further transmissions. In the case of Wireless Personal Area Networks (WPAN) which are more flexible, this is not usable. This is especially the case for Bluetooth. Some constraints in Bluetooth demands a more flexible on-demand ad hoc network compared to other types of ad hoc network protocols. Initially we found that creating a scatternet is not practically possible using Bluetooth version 1.1. The slave/slave bridge is not implemented into the hardware to create a scatternet. In this paper, we present a modified version of the Reverse Path Forwarding (RPF) algorithm to make it suitable for Bluetooth routing. With an on-demand ad hoc network solution together with the modified RPF algorithm we present a suitable solution for Bluetooth packets to be routed in a flexible ad hoc network. To be able to test the modified RPF and the on-demand ad hoc network, a test platform has also been developed.
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9.
  • Isaksson, Lennart, et al. (författare)
  • Validation of Simulations of Bluetooth's Frequency Hopping Spread Spectrum Technique
  • 2004
  • Konferensbidrag (refereegranskat)abstract
    • The need for performance studies avoiding expensive hardware installations and the lack of analytical models motivates the need of trustworthy simulation models for the cable-replacement technology Bluetooth. In this paper we show a detailed description of the Bluetooth technique and validation of different simulation models used today. To do this, a two-step approach for validation and credibility is necessary. First, a comprehensive empirical measurement was performed to establish a "status quo" of the behavior of today's Bluetooth technology. Second, a validation between empirical and simulation model is conducted to ensure the comparability. To accomplish these objectives we developed and validated a simulation model with frequency hopping algorithms and the whole state machine including collision detection. The results in form of histograms of different Bluetooth-specific durations indicate problems in case of already established simulation programs. So, finally, some changes and suggestions how to correct these defects are given.
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10.
  • Isaksson, Mikael, et al. (författare)
  • An environmental-sensitive BODIPY®-derivative with bioapplication : spectral and photophysical properties
  • 2003
  • Ingår i: Journal of Fluorescence. - 1053-0509 .- 1573-4994. ; 13:5, s. 379-84
  • Tidskriftsartikel (refereegranskat)abstract
    • A previously synthesised derivative of BODIPY aimed for sulfhydryl specific labelling of cysteine residues in proteins was studied. The spectral and photophysical properties of this derivative, N-(4,4-difluoro-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene-2-yl) iodoacetamide (NBDY) were characterised, and found to be considerably different from those of commonly used derivatives of BODIPY, e.g. N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-yl)methyl iodoacetamide. The absorption and fluorescence spectra, as well as fluorescence lifetimes and quantum yields of NBDY are quite sensitive to solvent properties. The fluorescence is effectively quenched by I– when NBDY is free in water or attached to Cys in different mutants of plasminogen activator inhibitor type 2 (PAI-2). A ground-state dimer forms when two NBDY groups are closely spaced in plasminogen activator inhibitor type 1 (PAI-1).
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