| 1. |
- Abbasi, R., et al.
(författare)
-
Background studies for acoustic neutrino detection at the South Pole
- 2012
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 35:6, s. 312-324
-
Tidskriftsartikel (refereegranskat)abstract
- The detection of acoustic signals from ultra-high energy neutrino interactions is a promising method to measure the flux of cosmogenic neutrinos expected on Earth. The energy threshold for this process depends strongly on the absolute noise level in the target material. The South Pole Acoustic Test Setup (SPATS), deployed in the upper part of four boreholes of the IceCube Neutrino Observatory, has monitored the noise in Antarctic ice at the geographic South Pole for more than two years down to 500 m depth. The noise is very stable and Gaussian distributed. Lacking an in situ calibration up to now, laboratory measurements have been used to estimate the absolute noise level in the 10-50 kHz frequency range to be smaller than 20 mPa. Using a threshold trigger, sensors of the South Pole Acoustic Test Setup registered acoustic events in the IceCube detector volume and its vicinity. Acoustic signals from refreezing IceCube holes and from anthropogenic sources have been used to test the localization of acoustic events. An upper limit on the neutrino flux at energies E-v>10(11) GeV is derived from acoustic data taken over eight months. (C) 2011 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Abbasi, R., et al.
(författare)
-
Calibration and characterization of the IceCube photomultiplier tube
- 2010
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 618:1-3, s. 139-152
-
Tidskriftsartikel (refereegranskat)abstract
- Over 5000 PMTs are being deployed at the South Pole to compose the IceCube neutrino observatory. Many are placed deep in the ice to detect Cherenkov light emitted by the products of high-energy neutrino interactions, and others are frozen into tanks on the surface to detect particles from atmospheric cosmic ray showers. IceCube is using the 10-in. diameter R7081-02 made by Hamamatsu Photonics. This paper describes the laboratory characterization and calibration of these PMTs before deployment. PMTs were illuminated with pulses ranging from single photons to saturation level. Parameterizations are given for the single photoelectron charge spectrum and the saturation behavior. Time resolution, late pulses and afterpulses are characterized. Because the PMTs are relatively large, the cathode sensitivity uniformity was measured. The absolute photon detection efficiency was calibrated using Rayleigh-scattered photons from a nitrogen laser. Measured characteristics are discussed in the context of their relevance to IceCube event reconstruction and simulation efforts. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 3. |
- Abbasi, R., et al.
(författare)
-
Constraints on high-energy neutrino emission from SN 2008D
- 2011
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 527:4, s. A28-
-
Tidskriftsartikel (refereegranskat)abstract
- SN 2008D, a core collapse supernova at a distance of 27 Mpc, was serendipitously discovered by the Swift satellite through an associated X-ray flash. Core collapse supernovae have been observed in association with long gamma-ray bursts and X-ray flashes and a physical connection is widely assumed. This connection could imply that some core collapse supernovae possess mildly relativistic jets in which high-energy neutrinos are produced through proton-proton collisions. The predicted neutrino spectra would be detectable by Cherenkov neutrino detectors like IceCube. A search for a neutrino signal in temporal and spatial correlation with the observed X-ray flash of SN 2008D was conducted using data taken in 2007-2008 with 22 strings of the IceCube detector. Events were selected based on a boosted decision tree classifier trained with simulated signal and experimental background data. The classifier was optimized to the position and a "soft jet" neutrino spectrum assumed for SN 2008D. Using three search windows placed around the X-ray peak, emission time scales from 100-10 000 s were probed. No events passing the cuts were observed in agreement with the signal expectation of 0.13 events. Upper limits on the muon neutrino flux from core collapse supernovae were derived for different emission time scales and the principal model parameters were constrained. While no meaningful limits can be given in the case of an isotropic neutrino emission, the parameter space for a jetted emission can be constrained. Future analyses with the full 86 string IceCube detector could detect up to similar to 100 events for a core-collapse supernova at 10 Mpc according to the soft jet model.
|
|
| 4. |
- Abbasi, R., et al.
(författare)
-
Constraints on the extremely-high energy cosmic neutrino flux with the IceCube 2008-2009 data
- 2011
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:9, s. 092003-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a search for extremely-high energy neutrinos with energies greater than 10(6) GeV using the data taken with the IceCube detector at the South Pole. The data was collected between April 2008 and May 2009 with the half-completed IceCube array. The absence of signal candidate events in the sample of 333.5 days of live time significantly improves model-independent limits from previous searches and allows to place a limit on the diffuse flux of cosmic neutrinos with an E-2 spectrum in the energy range 2.0 x 10(6) - 6.3 x 10(9) GeV to a level of E-2 phi <= 3.6 x 10(-8) GeV cm(-2) sec(-1) sr(-1).
|
|
| 5. |
- Abbasi, R, et al.
(författare)
-
Determination of the atmospheric neutrino flux and searches for new physics with AMANDA-II
- 2009
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 79, s. 102005-
-
Tidskriftsartikel (refereegranskat)abstract
- The AMANDA-II detector, operating since 2000 in the deep ice at the geographic South Pole, has accumulated a large sample of atmospheric muon neutrinos in the 100 GeV to 10 TeV energy range. The zenith angle and energy distribution of these events can be used to search for various phenomenological signatures of quantum gravity in the neutrino sector, such as violation of Lorentz invariance or quantum decoherence. Analyzing a set of 5511 candidate neutrino events collected during 1387 days of livetime from 2000 to 2006, we find no evidence for such effects and set upper limits on violation of Lorentz invariance and quantum decoherence parameters using a maximum likelihood method. Given the absence of evidence for new flavor-changing physics, we use the same methodology to determine the conventional atmospheric muon neutrino flux above 100 GeV.
|
|
| 6. |
- Abbasi, R, et al.
(författare)
-
Extending the Search for Neutrino Point Sources with IceCube above the Horizon
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 103:22, s. 221102-
-
Tidskriftsartikel (refereegranskat)abstract
- Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due to the exclusive selection of upward going events as a way of rejecting the atmospheric muon background. We show that the region above the horizon can be included by suppressing the background through energy-sensitive cuts. This improves the sensitivity above PeV energies, previously not accessible for declinations of more than a few degrees below the horizon due to the absorption of neutrinos in Earth. We present results based on data collected with 22 strings of IceCube, extending its field of view and energy reach for point source searches. No significant excess above the atmospheric background is observed in a sky scan and in tests of source candidates. Upper limits are reported, which for the first time cover point sources in the southern sky up to EeV energies.
|
|
| 7. |
- Abbasi, R, et al.
(författare)
-
FIRST NEUTRINO POINT-SOURCE RESULTS FROM THE 22 STRING ICECUBE DETECTOR
- 2009
-
Ingår i: Astrophysical Journal Letters. - 2041-8205. ; 701, s. L47-L51
-
Tidskriftsartikel (refereegranskat)abstract
- We present new results of searches for neutrino point sources in the northern sky, using data recorded in 2007-2008 with 22 strings of the IceCube detector (approximately one-fourth of the planned total) and 275.7 days of live time. The final sample of 5114 neutrino candidate events agrees well with the expected background of atmospheric muon neutrinos and a small component of atmospheric muons. No evidence of a point source is found, with the most significant excess of events in the sky at 2.2 sigma after accounting for all trials. The average upper limit over the northern sky for point sources of muon-neutrinos with E-2 spectrum is E-2 Phi(v mu) < 1.4 x 10(-11) TeV cm(-2) s(-1), in the energy range from 3 TeV to 3 PeV, improving the previous best average upper limit by the AMANDA-II detector by a factor of 2.
|
|
| 8. |
- Abbasi, R., et al.
(författare)
-
First search for atmospheric and extraterrestrial neutrino-induced cascades with the IceCube detector
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:7, s. 072001-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first search for atmospheric and for diffuse astrophysical neutrino-induced showers (cascades) in the IceCube detector using 257 days of data collected in the year 2007-2008 with 22 strings active. A total of 14 events with energies above 16 TeV remained after event selections in the diffuse analysis, with an expected total background contribution of 8.3 +/- 3.6. At 90% confidence we set an upper limit of E(2)Phi(90%CL) < 3.6 x 10(-7) GeV.cm(-2).s(-1).sr(-1) on the diffuse flux of neutrinos of all flavors in the energy range between 24 TeV and 6.6 PeV assuming that Phi proportional to E(-2) and the flavor composition of the nu(e):nu(mu):nu(tau) flux is 1:1:1 at the Earth. The atmospheric neutrino analysis was optimized for lower energies. A total of 12 events were observed with energies above 5 TeV. The observed number of events is consistent with the expected background, within the uncertainties.
|
|
| 9. |
- Abbasi, R., et al.
(författare)
-
First search for extremely high energy cosmogenic neutrinos with the IceCube Neutrino Observatory
- 2010
-
Ingår i: Physical review. D, Particles, fields, gravitation, and cosmology. - 1550-7998. ; 82:7, s. 072003-
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the results of the search for extremely-high energy neutrinos with energies above 10(7) GeV obtained with the partially (similar to 30%) constructed IceCube in 2007. From the absence of signal events in the sample of 242.1 days of effective live time, we derive a 90% C.L. model independent differential upper limit based on the number of signal events per energy decade at E-2 phi(ve+v mu+v tau) similar or equal to 1.4 x 10(-6) GeV cm(-2) sec(-1) sr(-1) for neutrinos in the energy range from 3 x 10(7) to 3 x 10(9) GeV.
|
|
| 10. |
- Abbasi, R., et al.
(författare)
-
IceTop : The surface component of IceCube
- 2013
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 700, s. 188-220
-
Tidskriftsartikel (refereegranskat)abstract
- IceTop, the surface component of the IceCube Neutrino Observatory at the South Pole, is an air shower array with an area of 1 km(2). The detector allows a detailed exploration of the mass composition of primary cosmic rays in the energy range from about 100 TeV to 1 EeV by exploiting the correlation between the shower energy measured in IceTop and the energy deposited by muons in the deep ice. In this paper we report on the technical design, construction and installation, the trigger and data acquisition systems as well as the software framework for calibration, reconstruction and simulation. Finally the first experience from commissioning and operating the detector and the performance as an air shower detector will be discussed.
|
|
| 11. |
- Abbasi, R., et al.
(författare)
-
Limits on a muon flux from Kaluza-Klein dark matter annihilations in the Sun from the IceCube 22-string detector
- 2010
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 81:5, s. 057101-
-
Tidskriftsartikel (refereegranskat)abstract
- A search for muon neutrinos from Kaluza-Klein dark matter annihilations in the Sun has been performed with the 22-string configuration of the IceCube neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured lightest Kaluza-Klein particle (LKP) WIMPs in the Sun and converted to limits on the LKP-proton cross sections for LKP masses in the range 250-3000 GeV. These results are the most stringent limits to date on LKP annihilation in the Sun.
|
|
| 12. |
- Abbasi, R, et al.
(författare)
-
Limits on a Muon Flux from Neutralino Annihilations in the Sun with the IceCube 22-String Detector
- 2009
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 102:20, s. 201302-
-
Tidskriftsartikel (refereegranskat)abstract
- A search for muon neutrinos from neutralino annihilations in the Sun has been performed with the IceCube 22-string neutrino detector using data collected in 104.3 days of live time in 2007. No excess over the expected atmospheric background has been observed. Upper limits have been obtained on the annihilation rate of captured neutralinos in the Sun and converted to limits on the weakly interacting massive particle (WIMP) proton cross sections for WIMP masses in the range 250-5000 GeV. These results are the most stringent limits to date on neutralino annihilation in the Sun.
|
|
| 13. |
- Abbasi, R., et al.
(författare)
-
Limits on Neutrino Emission from Gamma-Ray Bursts with the 40 String IceCube Detector
- 2011
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 106:14, s. 141101-
-
Tidskriftsartikel (refereegranskat)abstract
- IceCube has become the first neutrino telescope with a sensitivity below the TeV neutrino flux predicted from gamma-ray bursts if gamma-ray bursts are responsible for the observed cosmic-ray flux above 10(18) eV. Two separate analyses using the half-complete IceCube detector, one a dedicated search for neutrinos from p gamma interactions in the prompt phase of the gamma-ray burst fireball and the other a generic search for any neutrino emission from these sources over a wide range of energies and emission times, produced no evidence for neutrino emission, excluding prevailing models at 90% confidence.
|
|
| 14. |
- Abbasi, R., et al.
(författare)
-
Measurement of acoustic attenuation in South Pole ice
- 2011
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 34:6, s. 382-393
-
Tidskriftsartikel (refereegranskat)abstract
- Using the South Pole Acoustic Test Setup (SPATS) and a retrievable transmitter deployed in holes drilled for the IceCube experiment, we have measured the attenuation of acoustic signals by South Pole ice at depths between 190 m and 500 m. Three data sets, using different acoustic sources, have been analyzed and give consistent results. The method with the smallest systematic uncertainties yields an amplitude attenuation coefficient alpha = 3.20 +/- 0.57 km(-1) between 10 and 30 kHz, considerably larger than previous theoretical estimates. Expressed as an attenuation length, the analyses give a consistent result for lambda equivalent to 1/alpha of similar to 300 m with 20% uncertainty. No significant depth or frequency dependence has been found.
|
|
| 15. |
- Abbasi, R., et al.
(författare)
-
Measurement of sound speed vs. depth in South Pole ice for neutrino astronomy
- 2010
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 33:5-6, s. 277-286
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured the speed of both pressure waves and shear waves as a function of depth between 80 and 500 m depth in South Pole ice with better than 1% precision. The measurements were made using the South Pole Acoustic Test Setup (SPATS), an array of transmitters and sensors deployed in the ice at the South Pole in order to measure the acoustic properties relevant to acoustic detection of astrophysical neutrinos. The transmitters and sensors use piezoceramics operating at similar to 5-25 kHz. Between 200 m and 500 m depth, the measured profile is consistent with zero variation of the sound speed with depth, resulting in zero refraction, for both pressure and shear waves. We also performed a complementary study featuring an explosive signal propagating vertically from 50 to 2250 m depth, from which we determined a value for the pressure wave speed consistent with that determined for shallower depths, higher frequencies, and horizontal propagation with the SPATS sensors. The sound speed profile presented here can be used to achieve good acoustic source position and emission time reconstruction in general, and neutrino direction and energy reconstruction in particular. The reconstructed quantities could also help separate neutrino signals from background. (C) 2010 Elsevier B.V. All rights reserved.
|
|
| 16. |
- Abbasi, R., et al.
(författare)
-
Measurement of the anisotropy of cosmic-ray arrival directions with icecube
- 2010
-
Ingår i: The Astrophysical Journal Letters. - 2041-8205. ; 718, s. L194-L198
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi-TeV region in the Southern sky using data from the IceCube detector. Between 2007 June and 2008 March, the partially deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 m inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic-ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the southern sky. The data include 4.3 billion muons produced by downward-going cosmic-ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of similar to 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first-harmonic amplitude of (6.4 +/- 0.2 stat. +/- 0.8 syst.) x 10(-4).
|
|
| 17. |
- Abbasi, R., et al.
(författare)
-
Measurement of the atmospheric neutrino energy spectrum from 100 GeV to 400 TeV with IceCube
- 2011
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998 .- 1550-2368. ; 83:1, s. 012001-
-
Tidskriftsartikel (refereegranskat)abstract
- A measurement of the atmospheric muon neutrino energy spectrum from 100 GeV to 400 TeV was performed using a data sample of about 18 000 up-going atmospheric muon neutrino events in IceCube. Boosted decision trees were used for event selection to reject misreconstructed atmospheric muons and obtain a sample of up-going muon neutrino events. Background contamination in the final event sample is less than 1%. This is the first measurement of atmospheric neutrinos up to 400 TeV, and is fundamental to understanding the impact of this neutrino background on astrophysical neutrino observations with IceCube. The measured spectrum is consistent with predictions for the atmospheric nu(mu) + (nu) over bar (mu) flux.
|
|
| 18. |
- Abbasi, R., et al.
(författare)
-
Neutrino Analysis of the 2010 September Crab Nebula Flare and Time-Integrated Constraints on Neutrino Emission from the Crab Using Icecube
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 745:1, s. 45-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of a search for high-energy muon neutrinos with the IceCube detector in coincidence with the Crab Nebula flare reported on 2010 September by various experiments. Due to the unusual flaring state of the otherwise steady source we performed a prompt analysis of the 79-string configuration data to search for neutrinos that might be emitted along with the observed. gamma-rays. We performed two different and complementary data selections of neutrino events in the time window of 10 days around the flare. One event selection is optimized for discovery of E-upsilon(2). neutrino spectrum typical of first-order Fermi acceleration. A similar event selection has also been applied to the 40-string data to derive the time-integrated limits to the neutrino emission from the Crab. The other event selection was optimized for discovery of neutrino spectra with softer spectral index and TeV energy cutoffs as observed for various Galactic sources in. gamma-rays. The 90% confidence level (CL) best upper limits on the Crab flux during the 10 day flare are 4.73 x 10(-11) cm(-2) s(-1) TeV-1 for an E-upsilon(2). neutrino spectrum and 2.50 x 10(-10) cm(-2) s(-1) TeV-1 for a softer neutrino spectra of E-upsilon(-2.7), as indicated by Fermi measurements during the flare. In this paper, we also illustrate the impact of the time-integrated limit on the Crab neutrino steady emission. The limit obtained using 375.5 days of the 40-string configuration is compared to existing models of neutrino production from the Crab and its impact on astrophysical parameters is discussed. The most optimistic predictions of some models are already rejected by the IceCube neutrino telescope with more than 90% CL.
|
|
| 19. |
- Abbasi, R., et al.
(författare)
-
Observation of anisotropy in the arrival directions of galactic cosmic rays at multiple angular scales with IceCube
- 2011
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 740:1, s. 16-
-
Tidskriftsartikel (refereegranskat)abstract
- Between 2009 May and 2010 May, the IceCube neutrino detector at the South Pole recorded 32 billion muons generated in air showers produced by cosmic rays with a median energy of 20 TeV. With a data set of this size, it is possible to probe the southern sky for per-mil anisotropy on all angular scales in the arrival direction distribution of cosmic rays. Applying a power spectrum analysis to the relative intensity map of the cosmic ray flux in the southern hemisphere, we show that the arrival direction distribution is not isotropic, but shows significant structure on several angular scales. In addition to previously reported large-scale structure in the form of a strong dipole and quadrupole, the data show small-scale structure on scales between 15 degrees and 30 degrees. The skymap exhibits several localized regions of significant excess and deficit in cosmic ray intensity. The relative intensity of the smaller-scale structures is about a factor of five weaker than that of the dipole and quadrupole structure. The most significant structure, an excess localized at (right ascension alpha = 122 degrees.4 and declination d = -47 degrees.4), extends over at least 20 degrees in right ascension and has a post-trials significance of 5.3 sigma. The origin of this anisotropy is still unknown.
|
|
| 20. |
- Abbasi, R., et al.
(författare)
-
Search for a diffuse flux of astrophysical muon neutrinos with the IceCube 40-string detector
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:8, s. 082001-
-
Tidskriftsartikel (refereegranskat)abstract
- The IceCube Neutrino Observatory is a 1 km(3) detector currently taking data at the South Pole. One of the main strategies used to look for astrophysical neutrinos with IceCube is the search for a diffuse flux of high-energy neutrinos from unresolved sources. A hard energy spectrum of neutrinos from isotropically distributed astrophysical sources could manifest itself as a detectable signal that may be differentiated from the atmospheric neutrino background by spectral measurement. This analysis uses data from the IceCube detector collected in its half completed configuration which operated between April 2008 and May 2009 to search for a diffuse flux of astrophysical muon neutrinos. A total of 12 877 upward-going candidate neutrino events have been selected for this analysis. No evidence for a diffuse flux of astrophysical muon neutrinos was found in the data set leading to a 90% C. L. upper limit on the normalization of an E(-2) astrophysical nu(mu) flux of 8.9 x 10(-9) GeV cm(-2) s(-1) sr(-1). The analysis is sensitive in the energy range between 35 TeV and 7 PeV. The 12 877 candidate neutrino events are consistent with atmospheric muon neutrinos measured from 332 GeV to 84 TeV and no evidence for a prompt component to the atmospheric neutrino spectrum is found.
|
|
| 21. |
- Abbasi, R., et al.
(författare)
-
Search for a Lorentz-violating sidereal signal with atmospheric neutrinos in IceCube
- 2010
-
Ingår i: Physical Review D - Particles, Fields, Gravitation and Cosmology. - 1550-7998. ; 82, s. 112003-
-
Tidskriftsartikel (refereegranskat)abstract
- A search for sidereal modulation in the flux of atmospheric muon neutrinos in IceCube was performed. Such a signal could be an indication of Lorentz-violating physics. Neutrino oscillation models, derivable from extensions to the standard model, allow for neutrino oscillations that depend on the neutrino's direction of propagation. No such direction-dependent variation was found. A discrete Fourier transform method was used to constrain the Lorentz and CPT-violating coefficients in one of these models. Because of the unique high energy reach of IceCube, it was possible to improve constraints on certain Lorentz-violating oscillations by 3 orders of magnitude with respect to limits set by other experiments.
|
|
| 22. |
- Abbasi, R., et al.
(författare)
-
Search for dark matter from the Galactic halo with the IceCube Neutrino Telescope
- 2011
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 84:2, s. 022004-
-
Tidskriftsartikel (refereegranskat)abstract
- Self-annihilating or decaying dark matter in the Galactic halo might produce high energy neutrinos detectable with neutrino telescopes. We have conducted a search for such a signal using 276 days of data from the IceCube 22-string configuration detector acquired during 2007 and 2008. The effect of halo model choice in the extracted limit is reduced by performing a search that considers the outer halo region and not the Galactic Center. We constrain any large-scale neutrino anisotropy and are able to set a limit on the dark matter self-annihilation cross section of h similar or equal to 10(-22) cm(3) s(-1) for weakly interacting massive particle masses above 1 TeV, assuming a monochromatic neutrino line spectrum.
|
|
| 23. |
- Abbasi, R., et al.
(författare)
-
SEARCH FOR HIGH-ENERGY MUON NEUTRINOS FROM THE "NAKED-EYE" GRB 080319B WITH THE IceCube NEUTRINO TELESCOPE
- 2009
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 701:2, s. 1721-1731
-
Tidskriftsartikel (refereegranskat)abstract
- We report on a search with the IceCube detector for high-energy muon neutrinos from GRB 080319B, one of the brightest gamma-ray bursts (GRBs) ever observed. The fireball model predicts that a mean of 0.1 events should be detected by IceCube for a bulk Lorentz boost of the jet of 300. In both the direct on-time window of 66 s and an extended window of about 300 s around the GRB, no excess was found above background. The 90% CL upper limit on the number of track-like events from the GRB is 2.7, corresponding to a muon neutrino fluence limit of 9.5 x 10(-3) erg cm(-2) in the energy range between 120 TeV and 2.2 PeV, which contains 90% of the expected events.
|
|
| 24. |
- Abbasi, R., et al.
(författare)
-
Search for muon neutrinos from gamma-ray bursts with the IceCube neutrino telescope
- 2010
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 710:1, s. 346-359
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of searches for high-energy muon neutrinos from 41 gamma-ray bursts (GRBs) in the northern sky with the IceCube detector in its 22 string configuration active in 2007/2008. The searches cover both the prompt and a possible precursor emission as well as a model-independent, wide time window of -1 hr to + 3 hr around each GRB. In contrast to previous searches with a large GRB population, we do not utilize a standard Waxman-Bahcall GRB flux for the prompt emission but calculate individual neutrino spectra for all 41 GRBs from the burst parameters measured by satellites. For all of the three time windows, the best estimate for the number of signal events is zero. Therefore, we place 90% CL upper limits on the fluence from the prompt phase of 3.7 x 10(-3) erg cm(-2) (72 TeV-6.5 PeV) and on the fluence from the precursor phase of 2.3 x 10(-3) erg cm(-2) (2.2-55 TeV), where the quoted energy ranges contain 90% of the expected signal events in the detector. The 90% CL upper limit for the wide time window is 2.7 x 10(-3) erg cm(-2) (3 TeV-2.8 PeV) assuming an E-2 flux.
|
|
| 25. |
- Abbasi, R., et al.
(författare)
-
Search for neutrino-induced cascades with five years of AMANDA data
- 2011
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 34:6, s. 420-430
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the search for electromagnetic and hadronic showers ("cascades") produced by a diffuse flux of extraterrestrial neutrinos in the AMANDA neutrino telescope. Data for this analysis were recorded during 1001 days of detector livetime in the years 2000-2004. The observed event rates are consistent with the background expectation from atmospheric neutrinos and muons. An upper limit is derived for the diffuse flux of neutrinos of all flavors assuming a flavor ratio of v(e):v(mu):v(tau) = 1:1:1 at the detection site. The all-flavor flux of neutrinos with an energy spectrum Phi proportional to E-2 is less than 5.0 x 10(-7) GeV s(-1) sr(-1) cm(-2) at a 90% C.L. Here, 90% of the simulated signal would fall within the energy range 40 TeV to 9 PeV. We discuss flux limits in the context of several specific models of extraterrestrial and prompt atmospheric neutrino production.
|
|
| 26. |
- Abbasi, R., et al.
(författare)
-
Search for point sources of high energy neutrinos with final data from AMANDA-II
- 2009
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 79, s. 062001-
-
Tidskriftsartikel (refereegranskat)abstract
- We present a search for point sources of high energy neutrinos using 3.8 yr of data recorded by AMANDA-II during 2000-2006. After reconstructing muon tracks and applying selection criteria designed to optimally retain neutrino-induced events originating in the northern sky, we arrive at a sample of 6595 candidate events, predominantly from atmospheric neutrinos with primary energy 100 GeV to 8 TeV. Our search of this sample reveals no indications of a neutrino point source. We place the most stringent limits to date on E(-2) neutrino fluxes from points in the northern sky, with an average upper limit of E(2)Phi(nu mu)+nu(tau)<= 5.2x10(-11) TeV cm(-2) s(-1) on the sum of nu(mu) and nu(tau) fluxes, assumed equal, over the energy range from 1.9 TeV to 2.5 PeV.
|
|
| 27. |
- Abbasi, R., et al.
(författare)
-
Search for relativistic magnetic monopoles with the AMANDA-II neutrino telescope
- 2010
-
Ingår i: European Physical Journal C. - : Springer Science and Business Media LLC. - 1434-6044 .- 1434-6052. ; 69:3-4, s. 361-378
-
Tidskriftsartikel (refereegranskat)abstract
- We present the search for Cherenkov signatures from relativistic magnetic monopoles in data taken with the AMANDA-II detector, a neutrino telescope deployed in the Antarctic ice cap at the Geographic South Pole. The non-observation of a monopole signal in data collected during the year 2000 improves present experimental limits on the flux of relativistic magnetic monopoles: Our flux limit varies between 3.8x10(-17) cm(-2) s(-1) sr(-1) (for monopoles moving at the vacuum speed of light) and 8.8x10(-16) cm(-2) s(-1) sr(-1) (for monopoles moving at a speed beta=v/c=0.76, just above the Cherenkov threshold in ice). These limits apply to monopoles that are energetic enough to penetrate the Earth and enter the detector from below the horizon. The limit obtained for monopoles reaching the detector from above the horizon is less stringent by roughly an order of magnitude, due to the much larger background from down-going atmospheric muons. This looser limit is however valid for a larger class of magnetic monopoles, since the monopoles are not required to pass through the Earth.
|
|
| 28. |
- Abbasi, R., et al.
(författare)
-
The energy spectrum of atmospheric neutrinos between 2 and 200 TeV with the AMANDA-II detector
- 2010
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 34:1, s. 48-58
-
Tidskriftsartikel (refereegranskat)abstract
- The muon and anti-muon neutrino energy spectrum is determined from 2000-2003 AMANDA telescope data using regularised unfolding. This is the first measurement of atmospheric neutrinos in the energy range 2-200 TeV. The result is compared to different atmospheric neutrino models and it is compatible with the atmospheric neutrinos from pion and kaon decays. No significant contribution from charm had-ron decays or extraterrestrial neutrinos is detected. The capabilities to improve the measurement of the neutrino spectrum with the successor experiment IceCube are discussed.
|
|
| 29. |
- Abbasi, R., et al.
(författare)
-
The IceCube data acquisition system : Signal capture, digitization, and timestamping
- 2009
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 601:3, s. 294-316
-
Tidskriftsartikel (refereegranskat)abstract
- IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs). detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, functional capabilities, and initial performance of the DOM MB, and the operation of a combined array of DOMs as a system, are described here. Experience with the first InIce strings and the IceTop stations indicates that the system design and performance goals have been achieved. (c) 2009 Elsevier B.V. All rights reserved.
|
|
| 30. |
- Abbasi, R., et al.
(författare)
-
Time-dependent searches for point sources of neutrinos with the 40-string and 22-string configurations of IceCube
- 2012
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 744:1, s. 1-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents four searches for flaring sources of neutrinos using the IceCube neutrino telescope. For the first time, a search is performed over the entire parameter space of energy, direction, and time with sensitivity to neutrino flares lasting between 20 mu s and a year duration from astrophysical sources. Searches that integrate over time are less sensitive to flares because they are affected by a larger background of atmospheric neutrinos and muons that can be reduced by the use of additional timing information. Flaring sources considered here, such as active galactic nuclei, soft gamma-ray repeaters, and gamma-ray bursts, are promising candidate neutrino emitters. Two searches are "untriggered" in the sense that they look for any possible flare in the entire sky and from a predefined catalog of sources from which photon flares have been recorded. The other two searches are triggered by multi-wavelength information on flares from blazars and from a soft gamma-ray repeater. One triggered search uses lightcurves from Fermi-LAT which provides continuous monitoring. A second triggered search uses information where the flux states have been measured only for short periods of time near the flares. The untriggered searches use data taken by 40 strings of IceCube between 2008 April 5 and 2009 May 20. The triggered searches also use data taken by the 22-string configuration of IceCube operating between 2007 May 31 and 2008 April 5. The results from all four searches are compatible with a fluctuation of the background.
|
|
| 31. |
- Abbasi, R., et al.
(författare)
-
Time-integrated Searches for Point-like Sources of Neutrinos with the 40-string IceCube Detector
- 2011
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 732:1, s. 18-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the results of time-integrated searches for astrophysical neutrino sources in both the northern and southern skies. Data were collected using the partially completed IceCube detector in the 40-string configuration recorded between 2008 April 5 and 2009 May 20, totaling 375.5 days livetime. An unbinned maximum likelihood ratio method is used to search for astrophysical signals. The data sample contains 36,900 events: 14,121 from the northern sky, mostly muons induced by atmospheric neutrinos, and 22,779 from the southern sky, mostly high-energy atmospheric muons. The analysis includes searches for individual point sources and stacked searches for sources in a common class, sometimes including a spatial extent. While this analysis is sensitive to TeV-PeV energy neutrinos in the northern sky, it is primarily sensitive to neutrinos with energy greater than about 1 PeV in the southern sky. No evidence for a signal is found in any of the searches. Limits are set for neutrino fluxes from astrophysical sources over the entire sky and compared to predictions. The sensitivity is at least a factor of two better than previous searches (depending on declination), with 90% confidence level muon neutrino flux upper limits being between E(2)d Phi/dE similar to 2-200 x 10(-12) TeV cm(-2) s(-1) in the northern sky and between 3-700 x 10(-12) TeV cm(-2) s(-1) in the southern sky. The stacked source searches provide the best limits to specific source classes. The full IceCube detector is expected to improve the sensitivity to d Phi/dE proportional to E-2 sources by another factor of two in the first year of operation.
|
|
| 32. |
- Bendixen, Christine, 1965-
(författare)
-
Voices for Change : Hopes and costs for empowerment - a study on women's claims in the Egyptian revolution
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This study investigates women’s possibilities to actively participate in societal change in Egypt. It aims at enhancing the understanding of structural conditions for women’s agency and how these enables and/or restrains women’s participation in the aspiration for societal change as well as their aspiration to live a ‘full life’. Egypt was chosen as a field for studying women’s understanding of their opportunities of participation and empowerment before and during the revolution. The informants in the study are all consciously working for awareness and equality in society. Formal education in Egypt is criticized and the country suffers from a high illiteracy rate, making informal education an important way to attain knowledge that can assist women in their quest for societal change. The acknowledgment of participation as a human right is one of the issues women are fighting for in Egypt today. A specific interest in this study is what motivates some women to oppose social, cultural and political structures despite the often high personal cost, and how informal (educational) channels are being used in the quest for societal change. The theoretical construction in which the analysis is carried out is based on frictions between societal structures and agency, using the Capability Approach (Sen, 1999) which aims at understanding what agency women have in societal change. The concept of functionings is used to indicate what someone is able to do and be. By analyzing women’s valued functionings, their conditions and thus their sense of empowerment and their experienced opportunity costs emerge. Central to the analytically framed societal structures and how agency can be perceived within each structure are the social conversion factors, the norms that allow or hinder action. To frame the complexity of women’s conditions for active agency and the outcome of their actions, I use a theoretical framework that will comprise both goals and processes. Sen’s (1999) ideas on social choice along with Archer’s (1995) theory on social change, using her model of structural elaboration / reproduction, have proved useful when investigating women’s valued functionings and attained social changes. The results of the study show that when formal education is not adequate, knowledge is obtained outside the formal educational institutions. This is done through both non-formal and informal learning. However, to get access to informal learning, a number of valued functions have to be gained. These functionings are thus both conditions for change and an end in themselves. I try to show that the costs involved in transgressing the prevailing norms are high, but lack of hope, agency and empowerment are also experienced as a high cost for those who have, in fact, imagined another better life and are in opposition to the inhibitory societal structures. This is, however, a part of what motivates some women to continue to be involved in societal change in order to achieve a life they have reason to value.
|
|
| 33. |
- Bengtsson, Anki, 1959-
(författare)
-
Governance of Career Guidance : an enquiry into European policy
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overall aim of this thesis is to enquire into and problematize the governance of career guidance and how individuals’ career management is constructed within EU policy. The empirical material consists of European policy documents produced during 2000-2015. The two central research questions explore (1) how European career guidance is made governable, and (2) how individuals’ career management is constructed and governed. The Foucauldian governmentality perspective and the analytic method of problematization is utilized. The analysis focuses on the compositions of normative forms of reason, discursive practices and techniques by which governing is exercised and knowledge is produced. The thesis is based on four articles, three of which concern career guidance and career management. The fourth article concerns education of citizenship. The analysis shows that the formation of a policy space for comparison of national systems of career guidance is significant for making European career guidance amenable to governance. It is mobilized by governing practices for involvement of institutional actors and the construction of standards of performance. This form of governance becomes effective on the condition that institutional actors use and produce knowledge and practices about what works in career guidance, and this implies self-control and constant monitoring. It is a complex process of producing self-regulation of career guidance adjustable to change and innovation in which both standardization and modulation are inbuilt. Moreover, this is dependent on the interplay of governance and self-government. Knowledge and practices shape career management as an individual competence, which each individual is assumed to achieve. The use of guidance techniques supporting this design and self-regulating practices contributes to responsibilizing individuals to achieve this competence. Knowledge of individuals’ management of their careers includes civic competence. This led me to extend my use of the theoretical framework to investigate how knowledge of civic competence is constructed in European policy documents concerning teacher education from 2000 to 2012. My analysis shows that presumptions of teaching civic competence support the production of the active and learning subject.
|
|
| 34. |
|
|
| 35. |
|
|
| 36. |
|
|
| 37. |
- Gustavsson, Erik
(författare)
-
Om skolvalsfrågans rättvisedimensioner : En pedagogisk-filosofisk analys
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis explores how philosophical perspectives of justice can facilitate a critical discussion and a deepened understanding of the school choice issue and how it can be related to fundamental pedagogical ends of education, such as developing children´s autonomy and educating them to become democratic citizens. The methodological approach is based on John Dewey’s view of pragmatism, which argues for an experimental process of inquiry incorporating reflection on alternative lines of action. According to this approach, analyses of Swedish school choice policy are conducted based on three philosophical perspectives of justice: John Rawls’ justice as fairness, Nancy Fraser’s understanding of justice as three-dimensional and participative, and Amartya Sen’s capability approach. These perspectives clarify the relationship and meaning of three value premises that are prominent in the concept of school choice and foundational to liberal democratic societies: individual freedom, pluralism, and equality. Thus, the explorative approach highlights three answers to how the issue of school choice might be viewed from the perspective of justice. These answers are integrated into three criteria that serve as a pragmatistbased understanding of educational matters of justice, suggesting 1) that people should be viewed as active, social, and capable of intelligent change—individual and social—through reflective action; 2) that people should be given equal rights and opportunities to participate in and access influence over how they lead their lives; and 3) that societal organization (as well as the education system) should promote both people’s individual and common potential to act, which presupposes the striving toward full, free communication within and between social groups. Although the analyses of current Swedish school choice policy reveal increased criticism toward the contemporary system of school choice, the expressed policy strategies for dealing with injustice mainly aim to adjust the terms of choice within the realm of a market-based education, not critically examine the market structure, itself. The thesis argues for a renewed conversation about school choice, mirroring the pragmatic approach to inquiry while targeting the inherent democratic, communicative potential of schooling.
|
|
| 38. |
- Hansson, Klas, 1972-
(författare)
-
Water and Heat Transport in Road Structures : Development of Mechanistic Models
- 2005
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The coupled transport of water and heat, involving freezing and thawing, in the road structure and its immediate environment is important to consider for optimal design and maintenance of roads and when assessing solute transport, of e.g. de-icing salt, from roads. The objective of this study was to develop mechanistic models, and measurement techniques, suitable to describe and understand water flow and heat flux in road structures exposed to a cold climate. Freezing and thawing was accounted for by implementing new routines in two numerical models (HYDRUS1D/2D). The sensitivity of the model output to changes in parameter values and operational hydrological data was investigated by uncertainty and sensitivity analyses. The effect of rainfall event characteristics and asphalt fractures on the subsurface flow pattern was investigated by scenario modelling. The performance of water content reflectometers (WCR), measuring water content, was evaluated using measurements in two road structure materials. A numerical model was used to simulate WCR sensor response. The freezing/thawing routines were stable and provided results in agreement with laboratory measurements. Frost depth, thawing period, and freezing-induced water redistribution in a model road was greatly affected by groundwater level and type of subgrade. The simulated subsurface flow patterns corresponded well with published field observations. A new method was successful in enabling the application of time domain reflectometer (TDR) calibration equations to WCR output. The observed distortion in sampling volume for one of the road materials could be explained by the WCR sensor numerical model. Soil physical, hydrological, and hydraulic modules proved successful in simulating the coupled transport of water and heat in and on the road structure. It was demonstrated in this thesis that numerical models can improve the interpretation and explanation of measurements. The HYDRUS model was an accurate and pedagogical tool, clearly useful in road design and management.
|
|
| 39. |
|
|
| 40. |
|
|
| 41. |
- Johansson, Viktor, 1979-
(författare)
-
Dissonant Voices : Philosophy, Children's Literature, and Perfectionist Education
- 2013
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Dissonant Voices has a twofold aspiration. First, it is a philosophical treatment of everyday pedagogical interactions between children and their elders, between teachers and pupils. More specifically it is an exploration of the possibilities to go on with dissonant voices that interrupt established practices – our attunement – in behaviour, practice and thinking. Voices that are incomprehensible or expressions that are unacceptable, morally or otherwise. The text works on a tension between two inclinations: an inclination to wave off, discourage, or change an expression that is unacceptable or unintelligible; and an inclination to be tolerant and accept the dissonant expression as doing something worthwhile, but different.The second aspiration is a philosophical engagement with children’s literature. Reading children’s literature becomes a form of philosophising, a way to explore the complexity of a range of philosophical issues. This turn to literature marks a dissatisfaction with what philosophy can accomplish through argumentation and what philosophy can do with a particular and limited set of concepts for a subject, such as ethics. It is a way to go beyond philosophising as the founding of theories that justify particular responses. The philosophy of dissonance and children’s literature becomes a way to destabilise justifications of our established practices and ways of interacting.The philosophical investigations of dissonance are meant to make manifest the possibilities and risks of engaging in interactions beyond established agreement or attunements. Thinking of the dissonant voice as an expression beyond established practices calls for improvisation. Such improvisations become a perfectionist education where both the child and the elder, the teacher and the student, search for as yet unattained forms of interaction and take responsibility for every word and action of the interaction.The investigation goes through a number of picture books and novels for children such as Harry Potter, Garmann’s Summer, and books by Shaun Tan, Astrid Lindgren and Dr. Seuss as well narratives by J.R.R. Tolkien, Henrik Ibsen, Jane Austen and Henry David Thoreau. These works of fiction are read in conversation with philosophical works of, and inspired by, Ludwig Wittgenstein and Stanley Cavell, their moral perfectionism and ordinary language philosophy.
|
|
| 42. |
|
|
| 43. |
- Matta, Corrado, 1978-
(författare)
-
A Field of Veiled Continuities : Studies in the Methodology and Theory of Educational Research
- 2017
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Empirical educational research enjoys a methodological and theoretical debate that is characterized by a number of unresolved and lively debated controversies. This compilation thesis is an attempt to contribute to this debate using the toolbox of philosophy of science.The thesis consists of an introductory chapter and four essays. In the introductory chapter I identify three methodological and theoretical controversies that are discussed within the field of educational research. These are: 1) the controversy concerning the scientific status of educational research; 2) the controversy between cognitive and sociocultural theories of learning; and, 3) the controversy between realist and constructionist interpretations of theories of learning.I provide in the essays a critical assessment of the claims behind each of these controversies, and argue for an alternative reconstruction of these issues.In Essay I, I criticize a view about the interpretation of human action, labeled in the text as interpretivism. This view posits a sharp separation between the natural and social sciences, to the effect that the methods of the latter cannot be applied to the former. The first controversy seems to rest on this position. As I argue, the arguments in support of interpretivism are contradicted by actual research practice. I conclude that the interpretivistic claims lack support and that the general separation claim appears as problematic.A further debate has fueled the first controversy, that is, the supposed distinction between qualitative and quantitative methods. In Essay II, I argue against this distinction. More specifically, I discuss the concept of empirical support in the context of qualitative methods (for short, qualitative support). I provide arguments that although there are two specific and non-trivial properties of qualitative support, there is no methodological separation between quantitative and qualitative methods concerning empirical support.Considered together, the first two essays indicate two points of methodological continuity between educational research and other scientific practices (such as the natural sciences). I therefore conclude that the controversy concerning the scientific status of educational research rests in large part on unjustified claims.Essay III focuses on the second controversy. In this article I argue that Suárez’ inferential approach to the concept of scientific representation can be used as an account of scientific representation in learning, regardless of whether learning is understood as a cognitive or social phenomenon.The third controversy is discussed in Essay IV. Here, I discuss some ontological aspects of the framework of the actor-network theory. Reflecting on the use of this framework in the research field of Networked Learning, I argue that the assumption of an ontology of relations provides the solution for two puzzles about the ontology of networks. The relevance of my argument for the third controversy is that it suggests a point of connection between constructionist and realist interpretations of the ontology of learning.The last two essays suggest two points of continuities between theoretical frameworks that have been and still are argued to be incompatible.
|
|
| 44. |
- Oppenheim, Ronald W, et al.
(författare)
-
Developing postmitotic mammalian neurons in vivo lacking Apaf-1 undergo programmed cell death by a caspase-independent, nonapoptotic pathway involving autophagy.
- 2008
-
Ingår i: The Journal of neuroscience : the official journal of the Society for Neuroscience. - 1529-2401. ; 28:6, s. 1490-7
-
Tidskriftsartikel (refereegranskat)abstract
- Previous studies have shown that caspases and Apaf-1 are required for the normal programmed cell death (PCD) in vivo of immature postmitotic neurons and mitotically active neuronal precursor cells. In contrast, caspase activity is not necessary for the normal PCD of more mature postmitotic neurons that are establishing synaptic connections. Although normally these cells use caspases for PCD, in the absence of caspase activity these neurons undergo a distinct nonapoptotic type of degeneration. We examined the survival of these more mature postmitotic neuronal populations in mice in which Apaf-1 has been genetically deleted and find that they exhibit quantitatively normal PCD of developing postmitotic neurons. We next characterized the morphological mode of PCD in these mice and show that the neurons degenerate by a caspase-independent, nonapoptotic pathway that involves autophagy. However, autophagy does not appear to be involved in the normal PCD of postmitotic neurons in which caspases and Apaf-1 are present and functional because quantitatively normal neuronal PCD occurred in the absence of a key gene required for autophagy (ATG7). Finally, we examined the possible role of another caspase-independent type of neuronal PCD involving the apoptosis-inducing factor (AIF). Mice deficient in AIF also exhibit quantitatively normal PCD of postmitotic neurons after caspase inhibition. Together, these data indicate that, when key components of the type 1 apoptotic pathway (i.e., caspases and Apaf-1) are perturbed in vivo, developing postmitotic neurons nonetheless undergo quantitatively normal PCD by a caspase-independent pathway involving autophagy and not requiring AIF.
|
|
| 45. |
|
|
| 46. |
- Rosenquist, Joachim, 1980-
(författare)
-
Pluralism and unity in education : on education for democratic citizenship and personal autonomy in a pluralist society
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The overarching theme of this thesis concerns the possibility of balancing the values of unity and pluralism in education in developed nation states characterized by an increasing pluralism when it comes to the beliefs and values of its citizens. The author suggests that democracy has a normative basis in the principle of reciprocity which can be supported in an overlapping consensus by reasonable persons who differ in their moral, religious and philosophical beliefs. It is argued that this basis mandates a deliberative kind of democracy and that certain implications follow for how to understand the relation between democracy and individual rights, between democracy and religious belief and speech, and between rationality and deliberation, among other things. The author proceeds to discuss three educational issues in relation to the principle of reciprocity and its implications: 1. The legitimacy and content of a mandatory citizenship education, 2. Children’s rights to develop personal autonomy, 3. The opportunity for parents and children to choose which school children attend. These issues are important in relation to the question of how to balance unity and pluralism in education in that they concern the promotion of certain common beliefs, values and dispositions among citizens or the creation of a system of choice between schools with different profiles. The purpose of the discussion is to construct a theoretical position which balances the values of unity and pluralism in education, by giving diversity its due (contra communitarianism) while upholding a measure of unity (contra libertarianism and radical multiculturalism) which is located in the democratic and autonomy- promoting purposes of education rather than (exclusively) in its economic/vocational purposes (contra neo-liberalism). The discussions make use of political philosophy, educational philosophy and empirical research carried out by other researchers.
|
|
| 47. |
- Roth, Bodil, et al.
(författare)
-
Biochemical and immuno-pathological aspects of tissue transglutaminase in coeliac disease
- 2003
-
Ingår i: Autoimmunity. - : Informa UK Limited. - 0891-6934 .- 1607-842X. ; 36:4, s. 221-226
-
Tidskriftsartikel (refereegranskat)abstract
- Tissue transglutaminase (tTg) has been identified as the major autoantigen in coeliac disease (CD). ELISA methods have been developed for measuring the autoantibody. There are divergent reports on the effects of calcium on the antibody binding to tTg. Furthermore, zinc is a potent inhibitor of tTg. To better understand the role of transglutaminase in CD, we have studied the stability of commercial tTG, the effect of CD serum on tTg-activity and the effects of calcium and zinc on the antibody binding. The inclusion of calcium during the coating of the ELISA plates significantly increases the binding of the antibody, while zinc at physiological concentrations inhibits the binding. Moreover, our results show that commercial guinea pig liver Tg treated with calcium contains at least four major antigenic molecules and is a labile enzyme, which is degraded rapidly by contaminating proteases. Human serum contains anti-proteases that protect the enzyme. Probably, the labile character of commercial tTG explains the divergent reports on the effects of calcium on antibody binding. Finally, antibodies in serum from a CD patient do not seem to inhibit tTg activity. Hypothetically, low, intestinal Zn2+ -levels facilitate Ca2+ -activation of tTg, which deamidates gliadin. A complex between tTg and modified gliadin forms the antigen and triggers the immune reaction leading to manifest CD. Hypozincaemia secondary to villous atrophy aggravates the induced disease.
|
|
| 48. |
- Roth, Bodil, et al.
(författare)
-
Celiaki som modell för autoimmun sjukdom. Transglutaminas har nyckelroll--stressreaktion sätter fart på ond cirkel
- 2006
-
Ingår i: Läkartidningen. - 0023-7205. ; 103:19, s. 1523-1526
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The autoantigen of endomysial antibodies in coeliac disease has been found to be an enzyme, tissue transglutaminase. Zinc inhibits the calcium-dependent activation of this thiol enzyme and also decreases the affinity between transglutaminase and the antibodies. Physiologically, transglutaminases catalyse the formation of bridges between lysine- and glutamine-containing peptides. Theoretically, if accidentally activated, for example due to a stress-induced low concentration of intestinal zinc, tissue transglutaminase will sequentially deamidate specific glutamine residues in gliadins. During this process, an abnormally long-lived thioester intermediate between the active site cysteine of the enzyme and a previously, partly deamidated gliadine may trigger the T-cells in persons with HLA DQ2/DQ8, generating antibodies against both transglutaminase and gliadin. Furthermore, the resulting villous atrophy decreases the absorption of zinc, thus causing a vicious circle. In rheumatoid arthritis a similar pattern is observed with the formation of antibodies against citrulline as well as against the calcium-dependent citrullinating thiol-enzyme, peptidylargininedeiminase, which also is inhibited by zinc.
|
|
| 49. |
- Roth, Bodil, et al.
(författare)
-
Pathogenesis of autoimmune diseases: antibodies against transglutaminase, peptidylarginine deiminase and protein-bound citrulline in primary Sjögren's syndrome, multiple sclerosis and Alzheimer's disease.
- 2008
-
Ingår i: Scandinavian Journal of Immunology. - : Wiley. - 1365-3083 .- 0300-9475. ; 67:6, s. 626-631
-
Tidskriftsartikel (refereegranskat)abstract
- Coeliac disease (CD) is becoming a model for understanding the pathogenesis of autoimmune disorders. In CD, antibodies against transglutaminase 2 (TG2) and specific residues of gliadins have been identified. A similar situation is seen in rheumatoid arthritis (RA) with both anti-citrullinated protein antibodies (ACPA) and auto-antibodies against the citrullinating enzyme, peptidylarginine deiminase (PAD). Previously, we have suggested that a complex between an enzyme and its modified substrate constitutes the neoantigen in autoimmune diseases. Our hypothesis is challenged by findings in patients of primary Sjögren's syndrome (pSS) who do not express ACPA, but who have been reported to carry anti-PAD. The aims of our investigation were to reproduce the study claiming the presence of anti-PAD in pSS and screen for ACPA and antibodies against TG2 and PAD in pSS (n = 78), multiple sclerosis (MS) (n = 85) and Alzheimer's disease (AD) (n = 79) using ELISA. With blood donors (n = 100) as controls, no increased occurrence of autoantibodies was found among the patient groups tested. Contrary to what has been published previously, patients with pSS do not express anti-PAD. The hypothesis of a complex between an enzyme and its modified substrate constituting the neoantigen in autoimmune diseases is still valid. The prevalence of anti-PAD, anti-TG2 and ACPA is comparatively restricted. PAD and TG2 do not seem to be involved directly in autoimmune mechanisms in pSS, MS or AD.
|
|
| 50. |
|
|
