| 1. |
- Afzal, Zeeshan, 1991-
(författare)
-
Towards Secure Multipath TCP Communication
- 2017
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The evolution in networking coupled with an increasing demand to improve user experience has led to different proposals to extend the standard TCP. Multipath TCP (MPTCP) is one such extension that has the potential to overcome few inherent limitations in the standard TCP. While MPTCP's design and deployment progresses, most of the focus has been on its compatibility. The security aspect is confined to making sure that the MPTCP protocol itself offers the same security level as the standard TCP.The topic of this thesis is to investigate the unexpected security implications raised by using MPTCP in the traditional networking environment. The Internet of today has security middle-boxes that perform traffic analysis to detect intrusions and attacks. Such middle-boxes make use of different assumptions about the traffic, e.g., traffic from a single connection always arrives along the same path. This along with many other assumptions may not be true anymore with the advent of MPTCP as traffic can be fragmented and sent over multiple paths simultaneously.We investigate how practical it is to evade a security middle-box by fragmenting and sending traffic across multiple paths using MPTCP. Realistic attack traffic is used to evaluate such attacks against Snort IDS to show that these attacks are feasible. We then go on to propose possible solutions to detect such attacks and implement them in an MPTCP proxy. The proxy aims to extend the MPTCP performance advantages to servers that only support standard TCP, while ensuring that intrusions can be detected as before. Finally, we investigate the potential MPTCP scenario where security middle-boxes only have access to some of the traffic. We propose and implement an algorithm to perform intrusion detection in such situations and achieve a nearly 90% detection accuracy. Another contribution of this work is a tool, that converts IDS rules into equivalent attack traffic to automate the evaluation of a middle-box.
|
|
| 2. |
- Hedbom, Hans, et al.
(författare)
-
A Comparison of the Security of Windows NT and UNIX
- 1998
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a brief comparison of two operating systems, Windows NT and UNIX. The comparison covers two different aspects. First, we compare the main security features of the two operating systems and then we make a comparison of a selection of vulnerabilities most of which we know have been used for making real intrusions. We found that Windows NT has slightly more rigorous security features than standard UNIX but the two systems display similar vulnerabilities. The conclusion is that there are no significant differences in the real level of security between these systems
|
|
| 3. |
- Hedbom, Hans, et al.
(författare)
-
Analysis of the Security of Windows NT
- 1998
-
Rapport (refereegranskat)abstract
- This paper presents an analysis of the security in Windows NT 4.0, working in both stand-alone and networking mode. The objective of the work was to find out how secure this operating system actually is. A technical overview of the system, and in particular its security features is given. The system security was analyzed and practical intrusion attempts were made in order to verify vulnerabilities or to find new ones. All vulnerabilities are described in detail and classified according to a classification scheme. A comparison to commonly known UNIX weaknesses was made. It revealed generic similarities between the two systems to a surprisingly high degree. Finally a number of recommendations are given. The paper concludes that there are ample opportunities to improve the security of Windows NT. We have reason to believe that it is probably not higher than that of UNIX
|
|
| 4. |
- Hibar, Derrek P., et al.
(författare)
-
Novel genetic loci associated with hippocampal volume
- 2017
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The hippocampal formation is a brain structure integrally involved in episodic memory, spatial navigation, cognition and stress responsiveness. Structural abnormalities in hippocampal volume and shape are found in several common neuropsychiatric disorders. To identify the genetic underpinnings of hippocampal structure here we perform a genome-wide association study (GWAS) of 33,536 individuals and discover six independent loci significantly associated with hippocampal volume, four of them novel. Of the novel loci, three lie within genes (ASTN2, DPP4 and MAST4) and one is found 200 kb upstream of SHH. A hippocampal subfield analysis shows that a locus within the MSRB3 gene shows evidence of a localized effect along the dentate gyrus, subiculum, CA1 and fissure. Further, we show that genetic variants associated with decreased hippocampal volume are also associated with increased risk for Alzheimer's disease (r(g) = -0.155). Our findings suggest novel biological pathways through which human genetic variation influences hippocampal volume and risk for neuropsychiatric illness.
|
|
| 5. |
- Kiss, Mózsi, et al.
(författare)
-
The PoGOLite balloon-borne soft gamma-ray polarimeter
- 2008
-
Ingår i: COOL DISCS, HOT FLOWS. - : AIP. ; , s. 225-232
-
Konferensbidrag (refereegranskat)abstract
- Linearly polarized radiation in the hard X-ray/soft gamma-ray band is expected from a large variety of astronomical sources. We discuss the importance of polarimetric studies for several classes of sources - pulsars, accreting black holes. magnetic neutron stars and jets from active galaxies - and then describe PoGOLite, a balloon-borne instrument which is currently under construction and will be able to measure the polarization of electromagnetic radiation from such extra-solar objects in the energy range 25-80 keV.
|
|
| 6. |
|
|
| 7. |
- Takahashi, H., et al.
(författare)
-
A thermal-neutron detector with a phoswich system of LiCaAlF6 and BGO crystal scintillators onboard PoGOLite
- 2010
-
Ingår i: 2010 IEEE Nuclear Science Symposium, Medical Imaging Conference, NSS/MIC 2010 and 17th International Workshop on Room-Temperature Semiconductor X-ray and Gamma-ray Detectors, RTSD 2010. ; , s. 32-37
-
Konferensbidrag (refereegranskat)abstract
- To measure the flux of atmospheric neutrons and study the neutron contribution to the background of the main detector of the PoGOLite (Polarized Gamma-ray Observer) balloon-borne experiment, a thermal-neutron detector with a phoswich system of LiCaAlF6 (Eu) and BGO crystal scintillators is developed. The performance to separate thermal-neutron events from those of gamma-rays and charged particles is validated with 252Cf on ground. The detector is attached to the PoGOLite instrument and is launched in 2011 from the Esrange facility in the North of Sweden. Although the emission wavelength of the LiCaAlF6 (Ce) is 300 nm and overlaps with the absorption wavelength of the BGO, the phoswich capability of the LiCaAlF6 (Ce) with the BGO is also confirmed with installing a waveform shifter.
|
|
| 8. |
- Takahashi, H., et al.
(författare)
-
Beam test results of the polarized gamma-ray observer, PoGOLite
- 2008
-
Ingår i: 2008 IEEE NUCLEAR SCIENCE SYMPOSIUM AND MEDICAL IMAGING CONFERENCE (2008 NSS/MIC), VOLS 1-9. - 9781424427147 ; , s. 732-736
-
Konferensbidrag (refereegranskat)abstract
- The Polarized Gamma-ray Observer, PoGOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 mCrab celestial object in the energy range 25 #x2013;80 keV. During a beam test at KEK-PF in February 2008, 20 detector units were assembled, and a 50 keV X-ray beam with a polarization degree of #x223C;90% was irradiated at the center unit. Signals from all 20 units were fed into flightversion electronics consisting of six circuit boards (four waveform digitizer boards, one digital I/O board and one router board) and one microprocessor (SpaceCube), which communicate using a SpaceWire interface. One digitizer board, which can associate up to 8 PDCs, outputs a trigger signal. The digital I/O board handles the trigger and returns a data acquisition request if there is no veto signal (upper or pulse-shape discriminators) from any detector unit. This data acquisition system worked well, and the modulation factor was successfully measured to be #x223C;34%. These results confirmed the capabilities of both detector and data-acquisition system for a pathfinder flight planned in 2010.
|
|
| 9. |
- Takahashi, H., et al.
(författare)
-
The Polarized Gamma-Ray Observer, PoGOLite
- 2010
-
Ingår i: Transactions of the Japanese Society for Artificial Intelligence, Aerospace Technology Japan. - 1346-0714 .- 1346-0714. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The Polarized Gamma-ray Observer, PoGOLite, is a balloon experiment with the capability of detecting 10% polarization from a 200 mCrab celestial object in the energy-range 25–80 keV. During a beam test at KEK-PF in 2008, 19 detector units and one anti-coincidence detector were assembled, and a 50 keV X-ray beam with a polarization degree of ∼90% was irradiated at the center unit. Signals from all 20 units were fed into flight-version electronics consisting of six circuit boards (four waveform digitizer boards, one digital I/O board and one router board) and one microprocessor (SpaceCube), which communicate using a SpaceWire interface. One digitizer board, which can associate up to 8 detectors, outputs a trigger signal. The digital I/O board handles the trigger and returns a data acquisition request if there is no veto signal (upper or pulse-shape discriminators) from any detector unit. This data acquisition system worked well, and the modulation factor was successfully measured to be ∼34%. These results confirmed the capabilities of the data-acquisition system for a “pathfinder” flight planned in 2010.
|
|
| 10. |
- Abdollahi, S., et al.
(författare)
-
Fermi Large Area Telescope Fourth Source Catalog
- 2020
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 247:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present the fourth Fermi Large Area Telescope catalog (4FGL) of gamma-ray sources. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission in the energy range from 50 MeV to 1 TeV, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the 4FGL catalog has twice as much exposure as well as a number of analysis improvements, including an updated model for the Galactic diffuse gamma-ray emission, and two sets of light curves (one-year and two-month intervals). The 4FGL catalog includes 5064 sources above 4 sigma significance, for which we provide localization and spectral properties. Seventy-five sources are modeled explicitly as spatially extended, and overall, 358 sources are considered as identified based on angular extent, periodicity, or correlated variability observed at other wavelengths. For 1336 sources, we have not found plausible counterparts at other wavelengths. More than 3130 of the identified or associated sources are active galaxies of the blazar class, and 239 are pulsars.
|
|
| 11. |
- Acero, F., et al.
(författare)
-
FERMI LARGE AREA TELESCOPE THIRD SOURCE CATALOG
- 2015
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 218:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the third Fermi Large Area Telescope (LAT) source catalog (3FGL) of sources in the 100 MeV-300 GeV range. Based on the first 4 yr of science data from the Fermi Gamma-ray Space Telescope mission, it is the deepest yet in this energy range. Relative to the Second Fermi LAT catalog, the 3FGL catalog incorporates twice as much data, as well as a number of analysis improvements, including improved calibrations at the event reconstruction level, an updated model for Galactic diffuse.-ray emission, a refined procedure for source detection, and improved methods for associating LAT sources with potential counterparts at other wavelengths. The 3FGL catalog includes 3033 sources above 4 sigma significance, with source location regions, spectral properties, and monthly light curves for each. Of these, 78 are flagged as potentially being due to imperfections in the model for Galactic diffuse emission. Twenty-five sources are modeled explicitly as spatially extended, and overall 238 sources are considered as identified based on angular extent or correlated variability (periodic or otherwise) observed at other wavelengths. For 1010 sources we have not found plausible counterparts at other wavelengths. More than 1100 of the identified or associated sources are active galaxies of the blazar class; several other classes of non-blazar active galaxies are also represented in the 3FGL. Pulsars represent the largest Galactic source class. From source counts of Galactic sources we estimate that the contribution of unresolved sources to the Galactic diffuse emission is similar to 3% at 1 GeV.
|
|
| 12. |
- Ackermann, M., et al.
(författare)
-
Fermi-LAT Observations of the Gamma-Ray Burst GRB 130427A
- 2014
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6166, s. 42-47
-
Tidskriftsartikel (refereegranskat)abstract
- The observations of the exceptionally bright gamma-ray burst (GRB) 130427A by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope provide constraints on the nature of these unique astrophysical sources. GRB 130427A had the largest fluence, highest-energy photon (95 GeV), longest gamma-ray duration (20 hours), and one of the largest isotropic energy releases ever observed from a GRB. Temporal and spectral analyses of GRB 130427A challenge the widely accepted model that the nonthermal high-energy emission in the afterglow phase of GRBs is synchrotron emission radiated by electrons accelerated at an external shock.
|
|
| 13. |
- Ackermann, M., et al.
(författare)
-
FERMI LAT STACKING ANALYSIS OF SWIFT LOCALIZED GRBs
- 2016
-
Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 822:2
-
Tidskriftsartikel (refereegranskat)abstract
- We perform a comprehensive stacking analysis of data collected by the Fermi. Large Area Telescope (LAT) of gamma-ray bursts (GRBs) localized by the Swift. spacecraft, which were not detected by the LAT but which fell within the instrument's field of view at the time of trigger. We examine a total of 79 GRBs by comparing the observed counts over a range of time intervals to that expected from designated background orbits, as well as by using a joint likelihood technique to model the expected distribution of stacked counts. We find strong evidence for subthreshold emission at MeV to GeV energies using both techniques. This observed excess is detected during intervals that include and exceed the durations typically characterizing the prompt emission observed at keV energies and lasts at least 2700 s after the co-aligned burst trigger. By utilizing a novel cumulative likelihood analysis, we find that although a burst's prompt gamma-ray and afterglow X-ray flux both correlate with the strength of the subthreshold emission, the X-ray afterglow flux measured by Swift's X-ray Telescope at 11 hr post trigger correlates far more significantly. Overall, the extended nature of the subthreshold emission and its connection to the burst's afterglow brightness lend. further support to the external forward shock origin of the late-time emission detected by the LAT. These results suggest that the extended high-energy emission observed by the LAT may be a relatively common feature but remains undetected in a majority of bursts owing. to instrumental threshold effects.
|
|
| 14. |
- Ackermann, M., et al.
(författare)
-
The fermi large area telescope on orbit : Event classification, instrument response functions, and calibration
- 2012
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 203:1, s. 4-
-
Tidskriftsartikel (refereegranskat)abstract
- The Fermi Large Area Telescope (Fermi-LAT, hereafter LAT), the primary instrument on the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy γ-ray telescope, covering the energy range from 20MeV to more than 300GeV. During the first years of the mission, the LAT team has gained considerable insight into the in-flight performance of the instrument. Accordingly, we have updated the analysis used to reduce LAT data for public release as well as the instrument response functions (IRFs), the description of the instrument performance provided for data analysis. In this paper, we describe the effects that motivated these updates. Furthermore, we discuss how we originally derived IRFs from Monte Carlo simulations and later corrected those IRFs for discrepancies observed between flight and simulated data. We also give details of the validations performed using flight data and quantify the residual uncertainties in the IRFs. Finally, we describe techniques the LAT team has developed to propagate those uncertainties into estimates of the systematic errors on common measurements such as fluxes and spectra of astrophysical sources.
|
|
| 15. |
- Ackermann, M., et al.
(författare)
-
THE FIRST FERMI-LAT GAMMA-RAY BURST CATALOG
- 2013
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 209:1
-
Tidskriftsartikel (refereegranskat)abstract
- In three years of observations since the beginning of nominal science operations in 2008 August, the Large Area Telescope (LAT) on board the Fermi Gamma-Ray Space Telescope has observed high-energy (greater than or similar to 20 MeV) gamma-ray emission from 35 gamma-ray bursts (GRBs). Among these, 28 GRBs have been detected above 100 MeV and 7 GRBs above similar to 20 MeV. The first Fermi-LAT catalog of GRBs is a compilation of these detections and provides a systematic study of high-energy emission from GRBs for the first time. To generate the catalog, we examined 733 GRBs detected by the Gamma-Ray Burst Monitor (GBM) on Fermi and processed each of them using the same analysis sequence. Details of the methodology followed by the LAT collaboration for the GRB analysis are provided. We summarize the temporal and spectral properties of the LAT-detected GRBs. We also discuss characteristics of LAT-detected emission such as its delayed onset and longer duration compared with emission detected by the GBM, its power-law temporal decay at late times, and the fact that it is dominated by a power-law spectral component that appears in addition to the usual Band model.
|
|
| 16. |
- Ackermann, M., et al.
(författare)
-
The Second Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope
- 2011
-
Ingår i: Astrophysical Journal. - : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 743:2
-
Tidskriftsartikel (refereegranskat)abstract
- The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years of scientific operation is presented. The second LAT AGN catalog (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10°) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. However, some of these are affected by analysis issues and some are associated with multiple AGNs. Consequently, we define a Clean Sample which includes 886 AGNs, comprising 395 BL Lacertae objects (BL Lac objects), 310 flat-spectrum radio quasars (FSRQs), 157 candidate blazars of unknown type (i.e., with broadband blazar characteristics but with no optical spectral measurement yet), 8 misaligned AGNs, 4 narrow-line Seyfert 1 (NLS1s), 10 AGNs of other types, and 2 starburst galaxies. Where possible, the blazars have been further classified based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. While almost all FSRQs have a synchrotron-peak frequency <1014 Hz, about half of the BL Lac objects have a synchrotron-peak frequency >1015 Hz. The 2LAC represents a significant improvement relative to the first LAT AGN catalog (1LAC), with 52% more associated sources. The full characterization of the newly detected sources will require more broadband data. Various properties, such as γ-ray fluxes and photon power-law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities and their correlations are presented and discussed for the different blazar classes. The general trends observed in 1LAC are confirmed.
|
|
| 17. |
- Ahmadi Mehri, Vida
(författare)
-
Towards Automated Context-aware Vulnerability Risk Management
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The information security landscape continually evolves with increasing publicly known vulnerabilities (e.g., 25064 new vulnerabilities in 2022). Vulnerabilities play a prominent role in all types of security related attacks, including ransomware and data breaches. Vulnerability Risk Management (VRM) is an essential cyber defense mechanism to eliminate or reduce attack surfaces in information technology. VRM is a continuous procedure of identification, classification, evaluation, and remediation of vulnerabilities. The traditional VRM procedure is time-consuming as classification, evaluation, and remediation require skills and knowledge of specific computer systems, software, network, and security policies. Activities requiring human input slow down the VRM process, increasing the risk of exploiting a vulnerability.The thesis introduces the Automated Context-aware Vulnerability Risk Management (ACVRM) methodology to improve VRM procedures by automating the entire VRM cycle and reducing the procedure time and experts' intervention. ACVRM focuses on the challenging stages (i.e., classification, evaluation, and remediation) of VRM to support security experts in promptly prioritizing and patching the vulnerabilities. ACVRM concept is designed and implemented in a test environment for proof of concept. The efficiency of patch prioritization by ACVRM compared against a commercial vulnerability management tool (i.e., Rudder). ACVRM prioritized the vulnerability based on the patch score (i.e., the numeric representation of the vulnerability characteristic and the risk), the historical data, and dependencies. The experiments indicate that ACVRM could rank the vulnerabilities in the organization's context by weighting the criteria used in patch score calculation. The automated patch deployment is implemented with three use cases to investigate the impact of learning from historical events and dependencies on the success rate of the patch and human intervention. Our finding shows that ACVRM reduced the need for human actions, increased the ratio of successfully patched vulnerabilities, and decreased the cycle time of VRM process.
|
|
| 18. |
- Ajello, M., et al.
(författare)
-
Bright Gamma-Ray Flares Observed in GRB 131108A
- 2019
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics (IOP). - 2041-8205 .- 2041-8213. ; 886:2
-
Tidskriftsartikel (refereegranskat)abstract
- GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three ?-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the Gamma-ray Burst Monitor band (10 keV?10 MeV). The high-energy light curve of GRB 131108A (100 MeV?10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the ?-ray flares finds that the three flares are 6?20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6?2.0)10(?6) erg cm(?2), is comparable to that of emission during the steep decay phase, 1.710(?6) erg cm(?2). The total fluence from three ?-ray flares is 5.310(?6) erg cm(?2). The three ?-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in ?50% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect (
|
|
| 19. |
- Ajello, M., et al.
(författare)
-
Fermi and Swift Observations of GRB 190114C : Tracing the Evolution of High-energy Emission from Prompt to Afterglow
- 2020
-
Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 890:1
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma -ray Space Telescope and the Neil Gehrels Swift Observatory. The prompt gamma-ray emission was detected by the Fermi GRB Monitor (GBM), the Fermi Large Area Telescope (LAT), and the Swift Burst Alert Telescope (BAT) and the long-lived afterglow emission was subsequently observed by the GBM, LAT, Swift X-ray Telescope (XRT), and Swift UV Optical Telescope. The early -time observations reveal multiple emission components that evolve independently, with a delayed power-law component that exhibits significant spectral attenuation above 40 MeV in the first few seconds of the burst. This power-law component transitions to a harder spectrum that is consistent with the afterglow emission observed by the XRT at later times. This afterglow component is clearly identifiable in the GBM and BAT light curves as a slowly fading emission component on which the rest of the prompt emission is superimposed. As a result, we are able to observe the transition from internal-shock- to external-shock-dominated emission. We find that the temporal and spectral evolution of the broadband afterglow emission can be well modeled as synchrotron emission from a forward shock propagating into a wind -like circumstellar environment. We estimate the initial bulk Lorentz factor using the observed high-energy spectral cutoff. Considering the onset of the afterglow component, we constrain the deceleration radius at which this forward shock begins to radiate in order to estimate the maximum synchrotron energy as a function of time. We find that even in the LAT energy range, there exist high-energy photons that are in tension with the theoretical maximum energy that can be achieved through synchrotron emission from a shock. These violations of the maximum synchrotron energy are further compounded by the detection of very high-energy (VHE) emission above 300 GeV by MAGIC concurrent with our observations. We conclude that the observations of VHE photons from GRB 190114C necessitates either an additional emission mechanism at very high energies that is hidden in the synchrotron component in the LAT energy range, an acceleration mechanism that imparts energy to the particles at a rate that is faster than the electron synchrotron energy -loss rate, or revisions of the fundamental assumptions used in estimating the maximum photon energy attainable through the synchrotron process.
|
|
| 20. |
- Ajello, M., et al.
(författare)
-
Fermi Large Area Telescope Performance after 10 Years of Operation
- 2021
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 256:1
-
Tidskriftsartikel (refereegranskat)abstract
- The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the energy range from 30 MeV to more than 300 GeV. We describe the performance of the instrument at the 10 yr milestone. LAT performance remains well within the specifications defined during the planning phase, validating the design choices and supporting the compelling case to extend the duration of the Fermi mission. The details provided here will be useful when designing the next generation of high-energy gamma-ray observatories.
|
|
| 21. |
- Ajello, M., et al.
(författare)
-
Fermi-LAT Observations of LIGO/Virgo Event GW170817
- 2018
-
Ingår i: Astrophysical Journal. - : Institute of Physics (IOP). - 0004-637X .- 1538-4357. ; 861:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present the Fermi Large Area Telescope (LAT) observations of the binary neutron star merger event GW170817 and the associated short gamma-ray burst (SGRB) GRB 170817A detected by the Fermi Gamma-ray Burst Monitor. The LAT was entering the South Atlantic Anomaly at the time of the LIGO/Virgo trigger (t(GW)) and therefore cannot place constraints on the existence of high-energy (E > 100 MeV) emission associated with the moment of binary coalescence. We focus instead on constraining high-energy emission on longer timescales. No candidate electromagnetic counterpart was detected by the LAT on timescales of minutes, hours, or days after the LIGO/Virgo detection. The resulting flux upper bound (at 95% C. L.) from the LAT is 4.5. x. 10(-10) erg cm(-2) s(-1) in the 0.1-1 GeV range covering a period from tGW. +. 1153 s to t(GW). +. 2027 s. At the distance of GRB 170817A, this flux upper bound corresponds to a luminosity upper bound of 9.7. x. 10(43) erg s(-1), which is five orders of magnitude less luminous than the only other LAT SGRB with known redshift, GRB 090510. We also discuss the prospects for LAT detection of electromagnetic counterparts to future gravitational-wave events from Advanced LIGO/Virgo in the context of GW170817/GRB 170817A.
|
|
| 22. |
- Ajello, M., et al.
(författare)
-
High-energy emission from a magnetar giant flare in the Sculptor galaxy
- 2021
-
Ingår i: Nature Astronomy. - : Springer Nature. - 2397-3366. ; 5:4, s. 385-391
-
Tidskriftsartikel (refereegranskat)abstract
- Magnetars are the most highly magnetized neutron stars in the cosmos (with magnetic field 1013–1015 G). Giant flares from magnetars are rare, short-duration (about 0.1 s) bursts of hard X-rays and soft γ rays1,2. Owing to the limited sensitivity and energy coverage of previous telescopes, no magnetar giant flare has been detected at gigaelectronvolt (GeV) energies. Here, we report the discovery of GeV emission from a magnetar giant flare on 15 April 2020 (refs. 3,4 and A. J. Castro-Tirado et al., manuscript in preparation). The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected GeV γ rays from 19 s until 284 s after the initial detection of a signal in the megaelectronvolt (MeV) band. Our analysis shows that these γ rays are spatially associated with the nearby (3.5 megaparsecs) Sculptor galaxy and are unlikely to originate from a cosmological γ-ray burst. Thus, we infer that the γ rays originated with the magnetar giant flare in Sculptor. We suggest that the GeV signal is generated by an ultra-relativistic outflow that first radiates the prompt MeV-band photons, and then deposits its energy far from the stellar magnetosphere. After a propagation delay, the outflow interacts with environmental gas and produces shock waves that accelerate electrons to very high energies; these electrons then emit GeV γ rays as optically thin synchrotron radiation. This observation implies that a relativistic outflow is associated with the magnetar giant flare, and suggests the possibility that magnetars can power some short γ-ray bursts.
|
|
| 23. |
|
|
| 24. |
- Alendal, Gunnar, et al.
(författare)
-
Chip chop - smashing the mobile phone secure chip for fun and digital forensics
- 2021
-
Ingår i: Forensic Science International: Digital Investigation. - : Elsevier BV. - 2666-2817. ; 37
-
Tidskriftsartikel (refereegranskat)abstract
- Performing mobile phone acquisition today requires breaking—often hardware assisted—security. In recent years, Embedded Secure Element (eSE) hardware has been introduced in mobile phones, with a view towards increasing the security of critical system features and encrypted user data. The idea being that the eSE should remain secure even if the rest of the system is compromised. The eSE is set to become crucial to modern mobile phone security, challenging Digital Forensics. The eSE is designed to withstand both logical and physical attacks, including side channel attacks, and to keep the attack surface towards the rest of the system/phone small, and complexity low to minimise the risk of implementation errors.In this paper we adapt current state-of-the-art attacks to the eSE platform and present an attack on an eSE by Samsung, recently introduced in their premium mobile phones. We show how, with limited resources, our approach discovered a vulnerability that could be exploited, leading to a complete compromise of all the eSE security goals and a full loss of future eSE trust, as mitigation of our attack in already fielded devices is challenging. This eSE is Common Criteria EAL 5+ certified and our attack exposes the gap between intended and achieved security, undermining the implied trust in such certifications.We explain the eSE security design, the details of our attack, and discuss how a single vulnerability can have such devastating security results. The ultimate result of our research facilitates acquisition of affected devices, demonstrating use of offensive methods in advanced Digital Forensic Acquisition.
|
|
| 25. |
- Alendal, Gunnar, et al.
(författare)
-
DIGITAL FORENSIC ACQUISITION KILL CHAIN – ANALYSIS AND DEMONSTRATION
- 2021
-
Ingår i: Advances in Digital Forensics XVII. - Cham : Springer Nature. - 9783030883805 - 9783030883812 ; , s. 3-19
-
Bokkapitel (refereegranskat)abstract
- The increasing complexity and security of consumer products pose major challenges to digital forensics. Gaining access to encrypted user data without user credentials is a very difficult task. Such situations may require law enforcement to leverage offensive techniques – such as vulnerability exploitation – to bypass security measures in order to retrieve data in digital forensic investigations. This chapter proposes a digital forensic acquisition kill chain to assist law enforcement in acquiring forensic data using offensive techniques. The concept is discussed and examples are provided to illustrate the various kill chain phases. The anticipated results of applying the kill chain include improvements in performance and success rates in short-term, case-motivated, digital forensic acquisition scenarios as well as in long-term, case-independent planning and research scenarios focused on identifying vulnerabilities and leveraging them in digital forensic acquisition methods and tools.
|
|
| 26. |
- Alendal, Gunnar, et al.
(författare)
-
Exploiting Vendor-Defined Messages in the USB Power Delivery Protocol
- 2019
-
Ingår i: Advances in Digital Forensics XV. - Cham : Springer. - 9783030287511 - 9783030287528 ; , s. 101-118
-
Konferensbidrag (refereegranskat)abstract
- The USB Power Delivery protocol enables USB-connected devices to negotiate power delivery and exchange data over a single connection such as a USB Type-C cable. The protocol incorporates standard commands; however, it also enables vendors to add non-standard commands called vendor-defined messages. These messages are similar to the vendor-specific commands in the SCSI protocol, which enable vendors to specify undocumented commands to implement functionality that meets their needs. Such commands can be employed to enable firmware updates, memory dumps and even backdoors.This chapter analyzes vendor-defined message support in devices that employ the USB Power Delivery protocol, the ultimate goal being to identify messages that could be leveraged in digital forensic investigations to acquire data stored in the devices.© IFIP International Federation for Information Processing 2019
|
|
| 27. |
- Alendal, Gunnar, et al.
(författare)
-
Forensics acquisition – Analysis and circumvention of samsung secure boot enforced common criteria mode
- 2018
-
Ingår i: Digital Investigation. The International Journal of Digital Forensics and Incident Response. - Kidlington : Elsevier. - 1742-2876 .- 1873-202X. ; 24:Suppl., s. S60-S67
-
Tidskriftsartikel (refereegranskat)abstract
- The acquisition of data from mobile phones have been a mainstay of criminal digital forensics for a number of years now. However, this forensic acquisition is getting more and more difficult with the increasing security level and complexity of mobile phones (and other embedded devices). In addition, it is often difficult or impossible to get access to design specifications, documentation and source code. As a result, the forensic acquisition methods are also increasing in complexity, requiring an ever deeper understanding of the underlying technology and its security mechanisms. Forensic acquisition techniques are turning to more offensive solutions to bypass security mechanisms, through security vulnerabilities. Common Criteria mode is a security feature that increases the security level of Samsung devices, and thus make forensic acquisition more difficult for law enforcement. With no access to design documents or source code, we have reverse engineered how the Common Criteria mode is actually implemented and protected by Samsung's secure bootloader. We present how this security mode is enforced, security vulnerabilities therein, and how the discovered security vulnerabilities can be used to circumvent Common Criteria mode for further forensic acquisition. © 2018 The Author(s). Published by Elsevier Ltd on behalf of DFRWS.
|
|
| 28. |
- Alendal, Gunnar, et al.
(författare)
-
LEVERAGING USB POWER DELIVERY IMPLEMENTATIONS FOR DIGITAL FORENSIC ACQUISITION
- 2021
-
Ingår i: Advances in Digital Forensics XVII. - Cham : Springer Nature. - 9783030883805 - 9783030883812 ; , s. 111-133
-
Bokkapitel (refereegranskat)abstract
- Modern consumer devices present major challenges in digital forensic investigations due to security mechanisms that protect user data. The entire physical attack surface of a seized device such as a mobile phone must be considered in an effort to acquire data of forensic value. Several USB protocols have been introduced in recent years, including Power Delivery, which enables negotiations of power delivery to or from attached devices. A key feature is that the protocol is handled by dedicated hardware that is beyond the control of the device operating systems. This self-contained design is a security liability with its own attack surface and undocumented trust relationships with other peripherals and the main system-on-chips. This chapter presents a methodology for vulnerability discovery in USB Power Delivery implementations for Apple devices. The protocol and Apple-specific communications are reverse engineered, along with the firmware of the dedicated USB Power Delivery hardware. The investigation of the attack surface and potential security vulnerabilities can facilitate data acquisition in digital forensic investigations.
|
|
| 29. |
- Anderson, Brandon, et al.
(författare)
-
LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW 150914
- 2016
-
Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 826:1
-
Tidskriftsartikel (refereegranskat)abstract
- A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams.
|
|
| 30. |
- Anderson, Brandon, et al.
(författare)
-
SUPPLEMENT : LOCALIZATION AND BROADBAND FOLLOW-UP OF THE GRAVITATIONAL-WAVE TRANSIENT GW150914 (2016, ApJL, 826, L13)
- 2016
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 225:1
-
Tidskriftsartikel (refereegranskat)abstract
- This Supplement provides supporting material for Abbott et al. (2016a). We briefly summarize past electromagnetic (EM) follow-up efforts as well as the organization and policy of the current EM follow-up program. We compare the four probability sky maps produced for the gravitational-wave transient GW150914, and provide additional details of the EM follow-up observations that were performed in the different bands.
|
|
| 31. |
|
|
| 32. |
- Angelstam, Per, et al.
(författare)
-
Learning about the history of landscape use for the future : consequences for ecological and social systems in Swedish Bergslagen
- 2013
-
Ingår i: Ambio. - : Springer Science and Business Media LLC. - 0044-7447 .- 1654-7209. ; 42:2, s. 146-159
-
Tidskriftsartikel (refereegranskat)abstract
- Barriers and bridges to implement policies about sustainable development and sustainability commonly depend on the past development of social-ecological systems. Production of metals required integration of use of ore, streams for energy, and wood for bioenergy and construction, as well as of multiple societal actors. Focusing on the Swedish Bergslagen region as a case study we (1) describe the phases of natural resource use triggered by metallurgy, (2) the location and spatial extent of 22 definitions of Bergslagen divided into four zones as a proxy of cumulative pressure on landscapes, and (3) analyze the consequences for natural capital and society. We found clear gradients in industrial activity, stream alteration, and amount of natural forest from the core to the periphery of Bergslagen. Additionally, the legacy of top-down governance is linked to today's poorly diversified business sector and thus municipal vulnerability. Comparing the Bergslagen case study with other similar regions in Russia and Germany, we discuss the usefulness of multiple case studies.
|
|
| 33. |
|
|
| 34. |
- Axelsson, Johan, et al.
(författare)
-
In vivo photosensitizer tomography inside the human prostate
- 2009
-
Ingår i: Optics Letters. - 0146-9592. ; 34:3, s. 232-234
-
Tidskriftsartikel (refereegranskat)abstract
- Interstitial photodynamic therapy (IPDT) provides a promising means to treat large cancerous tumors and solid organs inside the human body. The treatment outcome is dependent on the distributions of light, photosensitizer, and tissue oxygenation. We present a scheme for reconstructing the spatial distribution of a fluorescent photosensitizer. The reconstruction is based on measurements performed in the human prostate, acquired during an ongoing IPDT clinical trial, as well as in optical phantoms. We show that in an experimental setup we can quantitatively reconstruct a fluorescent inclusion in a fluorescent background. We also show reconstructions from a patient showing a heterogeneous distribution of the photosensitizer mTHPC in the human prostate. (C) 2009 Optical Society of America
|
|
| 35. |
- Axelsson, Johan, et al.
(författare)
-
Prior information in fluorescence molecular tomography based on multispectral fluorescence emission
- 2007
-
Ingår i: Progress in Biomedical Optics and Imaging - Proceedings of SPIE. - : SPIE. - 1042-4687 .- 1605-7422. - 9780819465474 ; 6434, s. 4340-4340
-
Konferensbidrag (refereegranskat)abstract
- Fluorescence molecular tomography (FMT) suffers from inherent ill-posedness due to the vast number of possible solutions to the reconstruction problem. To increase the robustness of such a problem one need prior information. We present here a method for rendering a priori information of the position of a fluorescent inclusion inside turbid media. The method utilizes solely two spectral bands within the fluorescence spectrum emitted from the fluorophore. The method is presented and verified using experimental data from a tissue phantom. The confinement is also used to impose weights onto the voxels before the inversion of the linear set of equations describing the FMT problem.
|
|
| 36. |
- Axelsson, Johan, et al.
(författare)
-
Spatially varying regularization based on spectrally resolved fluorescence emission in fluorescence molecular tomography
- 2007
-
Ingår i: Optics Express. - 1094-4087. ; 15:21, s. 13574-13584
-
Tidskriftsartikel (refereegranskat)abstract
- Fluorescence molecular tomography suffers from being mathematically ill-conditioned resulting in non-unique solutions to the reconstruction problem. In an attempt to reduce the number of possible solutions in the underdetermined system of equations in the reconstruction, we present a method to retrieve a spatially varying regularization map outlining the feasible inclusion position. This approach can be made very simple by including a few multispectral recordings from only one source position. The results retrieved through tissue phantom experiments imply that initial reconstructions with spatially varying priors reduces artifacts and show slightly more accurate reconstruction results compared to reconstructions using no priors.
|
|
| 37. |
|
|
| 38. |
- Axelsson, Karin, et al.
(författare)
-
E-Health in care of older persons in the future
- 2010
-
Ingår i: Journal of Clinical Nursing. - 0962-1067 .- 1365-2702. ; 19:Suppl. 1, s. 54-
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Introduction: To achieve quality care in the person's home implies that the way we perform the care has to be developed. In this development new technology services, including mobile distance-spanning technology and information- and communication technology, has to be used. The aim of this presentation is to explore some issues important to consider before implementation of e-health services in care of older persons at home. Method: The presentation is based on studies where healthy older persons (n=23), older persons who had experience of being cared for with mobile distance-spanning technology (n=9) and general practitioners (n=17) were interviewed about their perceptions, views and experiences concerning the use of technology in care at home and quality care. The interviews were analysed by qualitative content analysis. Results: In the results from the different studies there were some common results. One was the importance of human meetings; another was that the person in need of care and the health professional need to know each other if virtual meetings should be possible. Other issues brought up in the different studies were trust, quality care, the need of combining home care services with visits at health care centres and hospitals, different technical equipment are only useful in specific circumstances, and mobile distance-spanning technology should not be looked at separately but as one part of a complex chain of health care services where all parts of the chain are needed. Conclusion: E-health including mobile distance-spanning technology and information- and communication technology is on its way to be accepted and used in home care for older persons. It is important that nurses as professionals actively take part in the development, designing and testing of the technical devices.
|
|
| 39. |
- Axelsson, Kristian F, 1973, et al.
(författare)
-
Risk of fracture in adults with type 2 diabetes in Sweden: A national cohort study
- 2023
-
Ingår i: Plos Medicine. - : Public Library of Science (PLoS). - 1549-1277 .- 1549-1676. ; 20:1
-
Tidskriftsartikel (refereegranskat)abstract
- Author summary Why was this study done? Type 2 diabetes mellitus (T2DM) is considered a risk factor for fracture but the evidence regarding the impact of T2DM on fracture risk is conflicting.We sought to determine if patients with T2DM had increased fracture risk and if so, to identify T2DM-related risk factors. What did the researchers do and find? We used a national register covering nearly all adult patients with T2DM in Sweden to compare the risk of fracture between T2DM patients ( = 580,127) and population controls ( = 580,127) without T2DM.In general, the risk of fracture was only marginally increased (by 1% for major osteoporotic fracture (MOF) and by 6% for hip fracture) for patients with T2DM compared to controls, but for patients with presence of risk factors, such as low BMI, long T2DM duration, insulin treatment, and/or low physical activity, the risk increase was more substantial (20% or higher) and potentially clinically relevant. What do these findings mean? Our findings suggest that T2DM per se should not be considered an important risk factor for fracture.Special consideration of the T2DM-related risk factors can be used to identify T2DM patients with a clinically relevant increased fracture risk.Further studies are needed to develop fracture risk calculators for different settings and populations for T2DM patients specifically. BackgroundType 2 diabetes mellitus (T2DM) is considered a risk factor for fracture but the evidence regarding the impact of T2DM on fracture risk is conflicting. The objective of the study was to determine if patients with T2DM have increased fracture risk and if T2DM-related risk factors could be identified. Methods and findingsIn this national cohort study in Sweden, we investigated the risk of fracture in 580,127 T2DM patients, identified through the national diabetes register including from both primary care and hospitals, and an equal number of population-based controls without diabetes matched for age, sex, and county from 2007 to 2017. The mean age at entry was 66.7 years and 43.6% were women. During a median follow-up time of 6.6 (interquartile range (IQR) 3.1 to 9.8) years, patients with T2DM had a marginally but significantly increased risk of major osteoporotic fracture (MOF) (hazard ratio (HR) 1.01 (95% confidence interval [CI] 1.00 to 1.03)) and hip fracture (HR 1.06 (95% CI 1.04 to 1.08)) compared to controls, associations that were only minimally affected (HR 1.05 (95% CI 1.03 to 1.06) and HR 1.11 (95% CI 1.09 to 1.14), respectively) by multivariable adjustment (age, sex, marital status, and an additional 20 variables related to general morbidity, cardiovascular status, risk of falls, and fracture). In a multivariable-adjusted Cox model, the proportion of the risk for all fracture outcomes (Heller's R2) explained by T2DM was below 0.1%. Among the T2DM patients, important risk factors for fracture were a low BMI (<25 kg/m(2)), long diabetes duration (>= 15 years), insulin treatment, and low physical activity. In total, 55% of the T2DM patients had none of these risk factors and a significantly lower fracture risk than their respective controls. The relatively short mean duration of T2DM and lack of bone density data, constitute limitations of the analysis. ConclusionIn this study, we observed only a marginally increased fracture risk in T2DM, a condition that explained less than 0.1% of the fracture risk. Consideration of the herein identified T2DM-related risk factors could be used to stratify T2DM patients according to fracture risk.
|
|
| 40. |
|
|
| 41. |
- Axelsson, Karin, et al.
(författare)
-
Projekt: Forskning - Omvårdnad - Äldre
- 2010
-
Annan publikation (populärvet., debatt m.m.)abstract
- Äldre personers föreställning om vård och användning av assisterande teknologi och service i händelse av vård Projektets övergripande syfte Syftet med studien var att beskriva äldre personers föreställningar om god vård och om användning av assisterande teknologi och service (ATS) i händelse av vård. Kort beskrivning av projektet Individuella intervjuer har genomförts med 12 par, där båda är > 70 år och utan någon form av regelbunden vård eller tillsyn i hemmet. Intervjuerna utgick från en tänkt situation (scenario) som komplicerades alltmer, där deltagarna ombads berätta om sin syn på god vård och användning av ATS både för egen del och även hur de trodde att partnerns inställning var. Intervjuerna var fokuserade till scenariot och utveckling av resonemang om god vård och användning av ATS vid vård och omsorg i hemmet. Intervjuerna spelades in på band, skrevs ut ordagrant och analyserades med kvalitativ innehållsanalys. Inför införandet av teknik vid vård i hemmet är det viktigt att beskriva hur äldre personer ser på användning av teknik och hur de ser på vad som är god vård.
|
|
| 42. |
- Axelsson, Karin, et al.
(författare)
-
Projekt: Friska äldre personers resonemang om användning av Informations- och Kommunikations Teknologi, IKT, vid vård och omsorg i hemmet
- 2010
-
Annan publikation (populärvet., debatt m.m.)abstract
- Projektets övergripande syfte Syftet med studien är att beskriva friska äldre personers resonemang om användning av Informations- och Kommunikationsteknologi (IKT) vid vård och omsorg i hemmet. Kort beskrivning av projektet Individuella intervjuer har genomförts av 12 par, där båda är > 70 år och de hade inte någon form av regelbunden vård eller tillsyn i hemmet. Intervjuerna utgick från en tänkt situation som komplicerades alltmer, där försökspersonerna ombads berätta om sin syn på användning av IKT både för egen del men även hur de trodde att partnerns inställning är. Intervjuerna var fokuserade till scenariot och utveckling av resonemang om användning av IKT vid vård och omsorg i hemmet. Intervjuerna är inspelade in på band och ordagrant utskrivna. Inför införandet av teknik vid vård i hemmet är det viktigt att beskriva hur äldre personer ser på användning av teknik.
|
|
| 43. |
- Axelsson, Karin, 1968-, et al.
(författare)
-
Reaching Communication Quality in Public E-Forms : A Communicative Perspective on E-Form Design
- 2007
-
Ingår i: Electronic Government. - Berlin, Heidelberg : Springer Berlin/Heidelberg. - 9783540744436 ; , s. 342-353
-
Konferensbidrag (refereegranskat)abstract
- This paper adopts a communication perspective on public electronic forms (e-forms). By doing so we define forms as instruments for communication and, thus, also instruments through which citizens perform different communicative actions towards government agencies. As such instruments, the forms might be more or less useful. The purpose of this paper is to explore what features of an e-form that increase the communication quality. We conduct a theoretical synthesis of three existing approaches for designing information systems. The result is a combined theory on key features of an e-form that make the establishment of communication quality more likely. The result consists of four key concepts, each of which give rise to one set of design principles for communication from the issuer of the e-form to the user (citizen), and one set of design principles for communication from the user (citizen) to the recipient of the e-form.
|
|
| 44. |
- Axelsson, Lena, et al.
(författare)
-
End of life of patients treated with haemodialysis as narrated by their close relatives
- 2015
-
Ingår i: Scandinavian Journal of Caring Sciences. - : Wiley. - 0283-9318 .- 1471-6712. ; 29:4, s. 776-784
-
Tidskriftsartikel (refereegranskat)abstract
- AIM: The study aimed to describe end of life for patients treated with maintenance haemodialysis as narrated by their close relatives.INTRODUCTION: Many patients undergoing haemodialysis are older, have several comorbidities and underestimated symptoms and are in their last year of life. To improve care, we need to know more about their end-of-life situation.DESIGN: Qualitative and descriptive.METHODS: Qualitative retrospective interviews were conducted with 14 close relatives of deceased haemodialysis patients (3-13 months after death). Data were analysed using qualitative content analysis. The study is ethically approved.FINDINGS: In the last months, a gradual deterioration in health with acute episodes necessitating hospital admissions was described. This involved diminishing living space and expressions of dejection, but also of joy. Three patterns emerged in the last weeks: uncertain anticipation of death as life fades away; awaiting death after haemodialysis withdrawal; and sudden but not unexpected death following intensive care. Findings show complexities of decisions on haemodialysis withdrawal.CONCLUSIONS: Different end-of-life patterns all involved increasingly complex care needs and existential issues. Findings show a need for earlier care planning. The identification of organisational factors to facilitate continuity and whole person care to meet these patients' specific care needs with their complex symptom burdens and comorbidities is needed. Findings indicate the need for integration of a palliative care approach in the treatment of patients in haemodialysis care.
|
|
| 45. |
- Axelsson, Lena
(författare)
-
Living with haemodialysis close to death - patients' and close relatives' experiences
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis is to generate understanding and knowledge a bout the experiences of patients living with haemodialysis, and their close relati ves, near the end of life. In studies I and II we conducted a series of 31 qualitative interviews over a period of 12 months with 8 severely ill patients (aged 66–87) treated with haemodialysis. For study I the text of the interviews was analysed using phenomenological hermeneutics to describe and to el ucidate the meanings of being severely ill living with haemodialysis when nearing end of life. For study II the text was analysed using qualitative content analysis to describe inner thoughts and feelings relating to death and dying of these patients. For studies III and IV, we conducted 14 retrospective qualitative interviews with close relatives of deceased patients treated with haemodialysis about th eir experiences during end of the patient’s life. For paper III the interview text was analysed usi ng phenomenological hermeneu tics to describe and elucidate the meanings of being a close relative at the end of life of a severely ill family member treated with maintenance haemodialysis. For paper IV the text was analysed using qualitative content analysis to describe end of life for the patients from the perspective of their close relatives. The findings of study I suggest that being severely i ll and living with haemodialysis near the end of life means living with suffering from a deteriorating body, a high symptom burden, and dependence on advanced medical technology, simultaneously with r econciliation and well-being. The meanings of living with illness and dialysis are intertwined with the meanings of being old. Study II shows that thoughts and feelings about deat h and dying are significant and complex for those living with haemodialysis as they approach the end of life. Patients experience a multifaceted presence of death. Their awareness of approaching death may include their repressing of thoughts of death, not as denial, but to allow them to focus on living as fully as possible the time they have left. Study III shows that close relatives strive to maintain balance and well-being for themselves and for the patient, which we interpreted as their striving to regain balance, and inner equilibrium in their changed and challenged rhythm of life. Study IV shows that after gradual deterioration and increasing care needs, older patients in haemodialysis care with co-morbidities follow three different main paths at the end of life: uncertain anticipation of death; awaiting death after dialysis withdrawal; and sudden but not unexpected death. The ends of their lives are marked by complex symptoms and existential issues related to haemodialysis treatment and withdrawal, and their uncertainty of what to expect at the end of life suggests the need for increased continuity and coordination of whole person care. Both patients and their close relatives are often alone with their existential thoughts. In their complex lifeworlds, intertwined meanings of living with illness and maintenance of life with haemodialysis treatment near the end of life show that patients live in a borderland of living-dying that is shared by the close relative. Patients and close relatives focus on living when death is close but uncertain, with severe illness and the maintenance of life through advanced technology. Integrating the philosophy of palliative care (with a focus on symptom relief, team work, communication, relationships, and support of family members) into dialysis care, may support health care professionals in haemodialysis units and other re nal contexts, to improve the care of severely ill patients, both earlier in their illness and as they approach the end of their lives.
|
|
| 46. |
- Axelsson, Lena, et al.
(författare)
-
Living with haemodialysis when nearing end of life
- 2012
-
Ingår i: Scandinavian Journal of Caring Sciences. - : Wiley. - 0283-9318 .- 1471-6712. ; 26:1, s. 45-52
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS AND OBJECTIVES: The aim of this study was to describe and to elucidate the meanings of being severely ill living with haemodialysis when nearing end of life.INTRODUCTION: To have end stage renal disease and to be treated with maintenance haemodialysis implies being dependent on lifelong treatment. Several studies have reported that these patients suffer a high symptom burden and an impaired quality of life due to both disease and treatment. In the dialysis unit, where the focus is on handling technology and maintaining life, end of life care may be neglected or overlooked. Nevertheless, mortality rates show that about one-fourth of patients in haemodialysis care are in their last year of life.DESIGN: A qualitative interpretative design was used.METHODS: Serial qualitative interviews over a period of 12 months were conducted with eight patients (aged 66-87). Altogether text of 31 interviews was interpreted using a phenomenological hermeneutical method in three phases. The study is ethically approved.FINDINGS: The structural analysis resulted in 11 subthemes and thereafter the following three themes were formulated; being subordinate to the deteriorating body, changing outlook on life and striving for upheld dignity. The comprehensive interpretation revealed that being severely ill living with haemodialysis near the end of life means living with suffering simultaneously with reconciliation and well-being. Further, the meanings are understood as intertwined with being old.CONCLUSIONS: Findings contribute to an increased awareness of the complexities of these patients' life worlds and their meanings, and thus of the importance to listen to their experiences and their understandings. Findings suggest that to integrate the philosophy of palliative care in haemodialysis units may improve care for patients who are living with haemodialysis and approaching the end of their lives.
|
|
| 47. |
- Axelsson, Lena, et al.
(författare)
-
Meanings of being a close relative of a family member treated with haemodialysis
- 2015
-
Ingår i: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 24:3/4, s. 447-456
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS AND OBJECTIVES:To describe and elucidate the meanings of being a close relative of a severely ill family member treated with maintenance haemodialysis approaching the end of life.BACKGROUND:End-stage renal disease together with comorbidities, haemodialysis treatment and high mortality rates also affects the lives of close relatives, who report burdens and impaired quality of life. To improve care, more understanding is needed of close relatives' experiences during these patients' end of life.DESIGN:This study has a qualitative interpretative design.METHODS:Fourteen retrospective qualitative interviews were conducted with close relatives (aged 48-93 years) of deceased patients who had been treated with haemodialysis. The interview text was interpreted using a phenomenological hermeneutical method in three phases.RESULTS:The findings of the structural analysis were formulated as six themes: Striving to be supportive and helpful without doing harm to the ill person's self; Needing increasing strength and support; Balancing the will to help with one's own ongoing life; Increasing responsibility involving dilemmas; Striving for a good life together in the present and Living with awareness of death.CONCLUSIONS:Close relatives strive for balance and well-being accompanying their ill family member through the end of life. They are facing moral dilemmas and growing demands as their responsibility increases with the deterioration of their family member. Support from and interaction with the healthcare professionals is then of significance.RELEVANCE TO CLINICAL PRACTICE:Findings challenge healthcare professionals in haemodialysis settings to identify close relatives' individual resources and needs towards the patients' end of life. Healthcare professionals in haemodialysis settings need to offer close relatives opportunities to talk about the future and what may be expected at end of life, with or without haemodialysis. They should also contact the closest relative after the death as they may need confirmation and closure.
|
|
| 48. |
- Axelsson, Lena, et al.
(författare)
-
Thoughts on death and dying when living with haemodialysis approaching end of life
- 2012
-
Ingår i: Journal of Clinical Nursing. - : Wiley. - 0962-1067 .- 1365-2702. ; 21:15-16, s. 2149-59
-
Tidskriftsartikel (refereegranskat)abstract
- AIMS AND OBJECTIVES: To describe inner thoughts and feelings relating to death and dying when living with haemodialysis approaching end of life.BACKGROUND: Patients who undergo maintenance haemodialysis suffer a significant symptom burden and an impaired quality of life. The high mortality rate in these patients indicates that about one-fourth of them are in their last year of life, suggesting the presence of death and dying in the haemodialysis unit.DESIGN: A qualitative descriptive design was used. Methods. A total of 31 qualitative interviews were conducted with eight patients (aged 66-87) over a period of 12 months. Qualitative content analysis was used to analyse data.RESULTS: The analysis revealed 10 subthemes that were sorted into three main themes. Being aware that death may be near comprises being reminded of death and dying by the deteriorating body, by the worsening conditions and deaths of fellow patients, and by knowing haemodialysis treatment as a border to death. Adapting to approaching death comprises looking upon death as natural, preparing to face death, hoping for a quick death and repressing thoughts of death and dying. Being alone with existential thoughts comprises a wish to avoid burdening family, lack of communication with healthcare professionals and reflections on haemodialysis withdrawal as an hypothetic option.CONCLUSIONS: Living with haemodialysis approaching, the end of life involves significant and complex existential issues and suffering, and patients are often alone with their existential thoughts.RELEVANCE TO CLINICAL PRACTICE: Nurses and other healthcare professionals in haemodialysis settings need to combine technical and medical abilities with committed listening and communication skills and be open to talking about death and dying, with sensitivity to individual and changeable needs.
|
|
| 49. |
- Axelsson, Morgan, et al.
(författare)
-
Column penetration tests for lime-cement columns in deep mixing - experiences in Sweden
- 2003
-
Ingår i: Geotechnical Special Publication. - 0895-0563. ; 120, s. 681-694
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper column penetration tests for lime-cement columns in deep soil mixing are reviewed. In principle, column penetration tests and reversed column penetration tests are considered. Improved test techniques are presented and discussed based on tests from two test sites in Sweden. The investigations indicate that the reversed column penetration test is the most suitable method for the primary quality test with reference to the uniformity and continuity of the columns. The probe should, however, be installed by the lime-cement column machine short after the manufacturing of the column to avoid disturbances in the mixing process and to enable a random test selection.
|
|
| 50. |
- Axelsson, Magnus, et al.
(författare)
-
Evolution of the 0.01-25 Hz power spectral components in Cygnus X-1
- 2005
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 438:3, s. 999-1012
-
Tidskriftsartikel (refereegranskat)abstract
- Analyzing the archival data from the Rossi X-ray Timing Explorer (RXTE), we study the power density spectra (PDS) of Cygnus X-1 from 1996 to 2003 in the frequency range of 0.01-25 Hz. Using a model consisting of one or two Lorentzians and/or an exponentially cut-off power-law, we are able to achieve a good fit to the PDS during the observations. With our model we are also able to track the evolution of the Lorentzian components through all spectral states of the source. We confirm the relation between characteristic frequencies seen both in black hole candidate and neutron star sources, and show the changes in this relation during the transitional and soft states of the source. The connection between the Lorentzian components is investigated by analyzing similarities and differences in their behavior. We find that the spectral state of the source can be uniquely determined from the parameters of these components. The parameter correlations can all be described by continuous functions, which differ between components. We discuss our results in the context of relativistic precession model for the accretion disk, and show a remarkable agreement between the model prediction and the data in the hard state. We estimate a value for the specific angular momentum of a* = 0.49 (-0.57) in the case of prograde (retrograde) rotation and an estimate for the inner radius of 22 to 50 (25 to 55) gravitational radii. Additional assumptions are required to explain the soft state data, and attempting to invoke rotational reversal for state transitions shows that it is insufficient to explain the differences between the hard and soft state data. © ESO 2005.
|
|
