| 1. |
|
|
| 2. |
- Acero, F., et al.
(författare)
-
Constraints on the galactic population of TeV pulsar wind nebulae using fermi large area telescope observations
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 773:1, s. 77-
-
Tidskriftsartikel (refereegranskat)abstract
- Pulsar wind nebulae (PWNe) have been established as the most populous class of TeV gamma-ray emitters. Since launch, the Fermi Large Area Telescope (LAT) has identified five high-energy (100 MeV < E < 100 GeV) gamma-ray sources as PWNe and detected a large number of PWN candidates, all powered by young and energetic pulsars. The wealth of multi-wavelength data available and the new results provided by Fermi-LAT give us an opportunity to find new PWNe and to explore the radiative processes taking place in known ones. The TeV gamma-ray unidentified (UNID) sources are the best candidates for finding new PWNe. Using 45 months of Fermi-LAT data for energies above 10 GeV, an analysis was performed near the position of 58 TeV PWNe and UNIDs within 5. of the Galactic plane to establish new constraints on PWN properties and find new clues on the nature of UNIDs. Of the 58 sources, 30 were detected, and this work provides their gamma-ray fluxes for energies above 10 GeV. The spectral energy distributions and upper limits, in the multi-wavelength context, also provide new information on the source nature and can help distinguish between emission scenarios, i.e., between classification as a pulsar candidate or as a PWN candidate. Six new GeV PWN candidates are described in detail and compared with existing models. A population study of GeV PWN candidates as a function of the pulsar/PWN system characteristics is presented.
|
|
| 3. |
- Ackermann, M., et al.
(författare)
-
THE FIRST FERMI-LAT CATALOG OF SOURCES ABOVE 10 GeV
- 2013
-
Ingår i: Astrophysical Journal Supplement Series. - : American Astronomical Society. - 0067-0049 .- 1538-4365. ; 209:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present a catalog of gamma-ray sources at energies above 10 GeV based on data from the Large Area Telescope (LAT) accumulated during the first 3 yr of the Fermi Gamma-ray Space Telescope mission. The first Fermi catalog of > 10 GeV sources (1FHL) has 514 sources. For each source we present location, spectrum, a measure of variability, and associations with cataloged sources at other wavelengths. We found that 449 (87%) could be associated with known sources, of which 393 (76% of the 1FHL sources) are active galactic nuclei. Of the 27 sources associated with known pulsars, we find 20 (12) to have significant pulsations in the range > 10 GeV (> 25 GeV). In this work we also report that, at energies above 10 GeV, unresolved sources account for 27% +/- 8% of the isotropic. gamma-ray background, while the unresolved Galactic population contributes only at the few percent level to the Galactic diffuse background. We also highlight the subset of the 1FHL sources that are best candidates for detection at energies above 50-100 GeV with current and future ground-based gamma-ray observatories.
|
|
| 4. |
- 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.
|
|
| 5. |
- Ackermann, M., et al.
(författare)
-
HIGH-ENERGY GAMMA-RAY EMISSION FROM SOLAR FLARES : SUMMARY OF FERMI LARGE AREA TELESCOPE DETECTIONS AND ANALYSIS OF TWO M-CLASS FLARES
- 2014
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 787:1, s. 15-
-
Tidskriftsartikel (refereegranskat)abstract
- We present the detections of 18 solar flares detected in high-energy gamma-rays (above 100 MeV) with the Fermi Large Area Telescope (LAT) during its first 4 yr of operation. This work suggests that particle acceleration up to very high energies in solar flares is more common than previously thought, occurring even in modest flares, and for longer durations. Interestingly, all these flares are associated with fairly fast coronal mass ejections (CMEs). We then describe the detailed temporal, spatial, and spectral characteristics of the first two long-lasting events: the 2011 March 7 flare, a moderate (M3.7) impulsive flare followed by slowly varying gamma-ray emission over 13 hr, and the 2011 June 7 M2.5 flare, which was followed by gamma-ray emission lasting for 2 hr. We compare the Fermi LAT data with X-ray and proton data measurements from GOES and RHESSI. We argue that the gamma-rays are more likely produced through pion decay than electron bremsstrahlung, and we find that the energy spectrum of the proton distribution softens during the extended emission of the 2011 March 7 flare. This would disfavor a trapping scenario for particles accelerated during the impulsive phase of the flare and point to a continuous acceleration process at play for the duration of the flares. CME shocks are known for accelerating the solar energetic particles (SEPs) observed in situ on similar timescales, but it might be challenging to explain the production of gamma-rays at the surface of the Sun while the CME is halfway to the Earth. A stochastic turbulence acceleration process occurring in the solar corona is another likely scenario. Detailed comparison of characteristics of SEPs and gamma-ray-emitting particles for several flares will be helpful to distinguish between these two possibilities.
|
|
| 6. |
- Ackermann, M., et al.
(författare)
-
Inferred Cosmic-Ray Spectrum from Fermi Large Area Telescope gamma-Ray Observations of Earth's Limb
- 2014
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 112:15, s. 151103-
-
Tidskriftsartikel (refereegranskat)abstract
- Recent accurate measurements of cosmic-ray (CR) species by ATIC-2, CREAM, and PAMELA reveal an unexpected hardening in the proton and He spectra above a few hundred GeV, a gradual softening of the spectra just below a few hundred GeV, and a harder spectrum of He compared to that of protons. These newly discovered features may offer a clue to the origin of high-energy CRs. We use the Fermi Large Area Telescope observations of the gamma-ray emission from Earth's limb for an indirect measurement of the local spectrum of CR protons in the energy range similar to 90 GeV-6 TeV (derived from a photon energy range 15 GeV-1 TeV). Our analysis shows that single power law and broken power law spectra fit the data equally well and yield a proton spectrum with index 2.68 +/- 0.04 and 2.61 +/- 0.08 above similar to 200 GeV, respectively.
|
|
| 7. |
- Ackermann, M., et al.
(författare)
-
The Fermi All-Sky Variability Analysis : A List Of Flaring Gamma-Ray Sources And The Search For Transients In Our Galaxy
- 2013
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 771:1, s. 57-
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we present the Fermi All-sky Variability Analysis (FAVA), a tool to systematically study the variability of the gamma-ray sky measured by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. For each direction on the sky, FAVA compares the number of gamma-rays observed in a given time window to the number of gamma-rays expected for the average emission detected from that direction. This method is used in weekly time intervals to derive a list of 215 flaring gamma-ray sources. We proceed to discuss the 27 sources found at Galactic latitudes smaller than 10 degrees and show that, despite their low latitudes, most of them are likely of extragalactic origin.
|
|
| 8. |
- Ackermann, M., et al.
(författare)
-
ASSOCIATING LONG-TERM gamma-RAY VARIABILITY WITH THE SUPERORBITAL PERIOD OF LS I+61 degrees 303
- 2013
-
Ingår i: ASTROPHYSICAL JOURNAL LETTERS. - 2041-8205. ; 773:2, s. L35-
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray binaries are stellar systems for which the spectral energy distribution (discounting the thermal stellar emission) peaks at high energies. Detected from radio to TeV gamma rays, the gamma-ray binary LS I + 61 degrees 303 is highly variable across all frequencies. One aspect of this system's variability is the modulation of its emission with the timescale set by the similar to 26.4960 day orbital period. Here we show that, during the time of our observations, the gamma-ray emission of LS I + 61 degrees 303 also presents a sinusoidal variability consistent with the previously known superorbital period of 1667 days. This modulation is more prominently seen at orbital phases around apastron, whereas it does not introduce a visible change close to periastron. It is also found in the appearance and disappearance of variability at the orbital period in the power spectrum of the data. This behavior could be explained by a quasi-cyclical evolution of the equatorial outflow of the Be companion star, whose features influence the conditions for generating gamma rays. These findings open the possibility to use gamma-ray observations to study the outflows of massive stars in eccentric binary systems.
|
|
| 9. |
- Ackermann, M., et al.
(författare)
-
THE THIRD CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE
- 2015
-
Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 810:1
-
Tidskriftsartikel (refereegranskat)abstract
- The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic greater than 25, between 2008 August 4 and 2012 July 31. The 3LAC includes 1591 AGNs located at high Galactic latitudes (vertical bar b vertical bar > 10 degrees), a 71% increase over the second catalog based on 2 years of data. There are 28 duplicate associations, thus 1563 of the 2192 high-latitude gamma-ray sources of the 3FGL catalog are AGNs. Most of them (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. Based on their gamma-ray spectral properties, these sources are evenly split between flat-spectrum radio quasars (FSRQs) and BL Lacs. The most abundant detected BL Lacs are of the high-synchrotron-peaked (HSP) type. About 50% of the BL Lacs have no measured redshifts. A few new rare outliers (HSP-FSRQs and high-luminosity HSP BL Lacs) are reported. The general properties of the 3LAC sample confirm previous findings from earlier catalogs. The fraction of 3LAC blazars in the total population of blazars listed in BZCAT remains non-negligible even at the faint ends of the BZCAT-blazar radio, optical, and X-ray flux distributions, which hints that even the faintest known blazars could eventually shine in gamma-rays at LAT-detection levels. The energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs.
|
|
| 10. |
|
|
| 11. |
- 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.
|
|
| 12. |
- Preece, R., et al.
(författare)
-
The First Pulse of the Extremely Bright GRB 130427A : A Test Lab for Synchrotron Shocks
- 2014
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 343:6166, s. 51-54
-
Tidskriftsartikel (refereegranskat)abstract
- Gamma-ray burst (GRB) 130427A is one of the most energetic GRBs ever observed. The initial pulse up to 2.5 seconds is possibly the brightest well-isolated pulse observed to date. A fine time resolution spectral analysis shows power-law decays of the peak energy from the onset of the pulse, consistent with models of internal synchrotron shock pulses. However, a strongly correlated power-law behavior is observed between the luminosity and the spectral peak energy that is inconsistent with curvature effects arising in the relativistic outflow. It is difficult for any of the existing models to account for all of the observed spectral and temporal behaviors simultaneously.
|
|
| 13. |
|
|
| 14. |
- Chauvin, Maxime, et al.
(författare)
-
Observation of polarized hard X-ray emission from the Crab by the PoGOLite Pathfinder
- 2016
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 456:1, s. L84-L88
-
Tidskriftsartikel (refereegranskat)abstract
- We have measured the linear polarization of hard X-ray emission from the Crab in a previously unexplored energy interval, 20-120 keV. The introduction of two new observational parameters, the polarization fraction and angle stands to disentangle geometrical and physical effects, thereby providing information on the pulsar wind geometry and magnetic field environment. Measurements are conducted using the PoGOLite Pathfinder - a balloon-borne polarimeter. Polarization is determined by measuring the azimuthal Compton scattering angle of incident X-rays in an array of plastic scintillators housed in an anticoincidence well. The polarimetric response has been characterized prior to flight using both polarized and unpolarized calibration sources. We address possible systematic effects through observations of a background field. The measured polarization fraction for the integrated Crab light curve is 18.4(-10.6)(+9.8) per cent, corresponding to an upper limit (99 per cent credibility) of 42.4 per cent, for a polarization angle of (149.2 +/- 16.0)degrees.
|
|
| 15. |
- Makii, H., et al.
(författare)
-
Effects of the nuclear structure of fission fragments on the high-energy prompt fission γ -ray spectrum in U 235 (nth,f)
- 2019
-
Ingår i: Physical Review C. - 2469-9985. ; 100:4
-
Tidskriftsartikel (refereegranskat)abstract
- The prompt fission γ-ray energy spectrum for cold-neutron-induced fission of U235 was measured in the energy range Eγ=0.8-20MeV, by gaining a factor of about 105 in statistics compared to the measurements performed so far. The spectrum exhibits local bump structures at Eγ≈4MeV and ≈6MeV, and also a broad one at ≈15MeV. In order to understand the origins of these bumps, the γ-ray spectra were calculated using a statistical Hauser-Feshbach model, taking into account the deexcitation of all the possible primary fission fragments. It is shown that the bump at ≈4MeV is created by the transitions between the discrete levels in the fragments around Sn132, and the bump at ≈6MeV mostly comes from the complementary light fragments. It is also indicated that a limited number of nuclides, which have high-spin states at low excitation energies, can contribute to the bump structure around Eγ≈15MeV, induced by the transition feeding into the low-lying high-spin states.
|
|
| 16. |
- Chauvin, Maxime, et al.
(författare)
-
Shedding new light on the Crab with polarized X-rays
- 2017
-
Ingår i: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 7:7816, s. 1-6
-
Tidskriftsartikel (refereegranskat)abstract
- Strong magnetic fields, synchrotron emission, and Compton scattering are omnipresent in compactcelestial X-ray sources. Emissions in the X-ray energy band are consequently expected to be linearlypolarized. X-ray polarimetry provides a unique diagnostic to study the location and fundamentalmechanisms behind emission processes. The polarization of emissions from a bright celestial X-raysource, the Crab, is reported here for the first time in the hard X-ray band (~20–160 keV). The Crab isa complex system consisting of a central pulsar, a diffuse pulsar wind nebula, as well as structures inthe inner nebula including a jet and torus. Measurements are made by a purpose-built and calibratedpolarimeter, PoGO+. The polarization vector is found to be aligned with the spin axis of the pulsar for apolarization fraction, PF = (20.9 ± 5.0)%. This is higher than that of the optical diffuse nebula, implyinga more compact emission site, though not as compact as, e.g., the synchrotron knot. Contrary tomeasurements at higher energies, no significant temporal evolution of phase-integrated polarisationparameters is observed. The polarization parameters for the pulsar itself are measured for the first timein the X-ray energy band and are consistent with observations at optical wavelengths.
|
|
| 17. |
- Chauvin, Maxime, et al.
(författare)
-
The PoGO plus view on Crab off-pulse hard X-ray polarization
- 2018
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 477:1, s. L45-L49
-
Tidskriftsartikel (refereegranskat)abstract
- The linear polarization fraction (PF) and angle of the hard X-ray emission from the Crab provide unique insight into high-energy radiation mechanisms, complementing the usual imaging, timing, and spectroscopic approaches. Results have recently been presented by two missions operating in partially overlapping energy bands, PoGO+ (18-160 keV) and AstroSat CZTI (100-380 keV). We previously reported PoGO+ results on the polarization parameters integrated across the light curve and for the entire nebula-dominated off-pulse region. We now introduce finer phase binning, in light of the AstroSat CZTI claim that the PF varies across the off-pulse region. Since both missions are operating in a regime where errors on the reconstructed polarization parameters are non-Gaussian, we adopt a Bayesian approach to compare results from each mission. We find no statistically significant variation in off-pulse polarization parameters, neither when considering the mission data separately nor when they are combined. This supports expectations from standard high-energy emission models.
|
|
| 18. |
- Ferreira, Letícia T, et al.
(författare)
-
Chemical Genomic Profiling Unveils the in Vitro and in Vivo Antiplasmodial Mechanism of Açaí (Euterpe oleracea Mart.) Polyphenols.
- 2019
-
Ingår i: ACS Omega. - : American Chemical Society (ACS). - 2470-1343. ; 4:13, s. 15628-15635
-
Tidskriftsartikel (refereegranskat)abstract
- Malaria remains a major detrimental parasitic disease in the developing world, with more than 200 million cases annually. Widespread drug-resistant parasite strains push for the development of novel antimalarial drugs. Plant-derived natural products are key sources of antimalarial molecules. Euterpe oleracea Martius ("açaí") originates from Brazil and has anti-inflammatory and antineoplasic properties. Here, we evaluated the antimalarial efficacy of three phenolic fractions of açaí; total phenolics (1), nonanthocyanin phenolics (2), and total anthocyanins (3). In vitro, fraction 2 moderately inhibited parasite growth in chloroquine-sensitive (HB3) and multiresistant (Dd2) Plasmodium falciparum strains, while none of the fractions was toxic to noncancer cells. Despite the limited activity in vitro, the oral treatment with 20 mg/kg of fraction 1 reduced parasitemia by 89.4% in Plasmodium chabaudi-infected mice and prolonged survival. Contrasting in vitro and in vivo activities of 1 suggest key antiplasmodial roles for polyphenol metabolites rather than the fraction itself. Finally, we performed haploinsufficiency chemical genomic profiling (HIP) utilizing heterozygous Saccharomyces cerevisiae deletion mutants to identify molecular mechanisms of açaí fractions. HIP results indicate proteostasis as the main cellular pathway affected by fraction 2. These results open avenues to develop açaí polyphenols as potential new antimalarial candidates.
|
|
| 19. |
- Kole, Merlin, et al.
(författare)
-
Neutron background detection for a hard X-ray balloon-borne polarimeter
- 2014
-
Ingår i: Proceedings of Science. - : Proceedings of Science (PoS).
-
Konferensbidrag (refereegranskat)abstract
- PoGOLite is a balloon-borne hard X-ray polarimeter. It determines polarisation by measuring the azimuthal angular distribution of Compton scattered photons in a plastic scintillator array. The use of an all-plastic target yields a relatively large, low-mass detection area. The dominant source of background for these measurements has been shown, through Geant4 simulations, to originate from high energy (MeV range) atmospheric neutrons. Neutrons can pass the instrument's Bismuth Germanium Oxide (BGO) anti-coincidence shield undetected and subsequently scatter between plastic scintillator elements to produce a polarisation signature. A passive 15 cm thick polyethylene shield surrounding the polarimeter reduces the neutron induced background by an order of magnitude. The background level remains however significant, prompting the need for active monitoring of the continuously changing neutron flux. For this purpose PoGOLite makes use of a phoswich scintillator cell. The phoswich cell consists of a 5 mm thick Lithium Calcium Aluminium Fluoride (LiCAF) scintillator, used for neutron detection. The LiCAF is surrounded by a BGO anti-coincidence system. This small light weight detector can therefore be used to measure the neutron flux even in high radiation environments. This type of neutron detector was tested on a separate dedicated stratospheric balloon mission in March 2013, called PoGOLino, prior to the PoGOLite flight which took place in July 2013. Results from the test flight and implications for the measurements performed on the PoGOLite flight will be discussed.
|
|
| 20. |
- Tobias, Deirdre K, et al.
(författare)
-
Second international consensus report on gaps and opportunities for the clinical translation of precision diabetes medicine
- 2023
-
Ingår i: Nature Medicine. - 1546-170X. ; 29:10, s. 2438-2457
-
Forskningsöversikt (refereegranskat)abstract
- Precision medicine is part of the logical evolution of contemporary evidence-based medicine that seeks to reduce errors and optimize outcomes when making medical decisions and health recommendations. Diabetes affects hundreds of millions of people worldwide, many of whom will develop life-threatening complications and die prematurely. Precision medicine can potentially address this enormous problem by accounting for heterogeneity in the etiology, clinical presentation and pathogenesis of common forms of diabetes and risks of complications. This second international consensus report on precision diabetes medicine summarizes the findings from a systematic evidence review across the key pillars of precision medicine (prevention, diagnosis, treatment, prognosis) in four recognized forms of diabetes (monogenic, gestational, type 1, type 2). These reviews address key questions about the translation of precision medicine research into practice. Although not complete, owing to the vast literature on this topic, they revealed opportunities for the immediate or near-term clinical implementation of precision diabetes medicine; furthermore, we expose important gaps in knowledge, focusing on the need to obtain new clinically relevant evidence. Gaps include the need for common standards for clinical readiness, including consideration of cost-effectiveness, health equity, predictive accuracy, liability and accessibility. Key milestones are outlined for the broad clinical implementation of precision diabetes medicine.
|
|
| 21. |
- Chauvin, Maxime, et al.
(författare)
-
The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter
- 2016
-
Ingår i: Experimental astronomy. - : Springer Science and Business Media LLC. - 0922-6435 .- 1572-9508. ; 41:1, s. 17-41
-
Tidskriftsartikel (refereegranskat)abstract
- In the 50 years since the advent of X-ray astronomy there have been many scientific advances due to the development of new experimental techniques for detecting and characterising X-rays. Observations of X-ray polarisation have, however, not undergone a similar development. This is a shortcoming since a plethora of open questions related to the nature of X-ray sources could be resolved through measurements of the linear polarisation of emitted X-rays. The PoGOLite Pathfinder is a balloon-borne hard X-ray polarimeter operating in the 25-240 keV energy band from a stabilised observation platform. Polarisation is determined using coincident energy deposits in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. The PoGOLite Pathfinder was launched from the SSC Esrange Space Centre in July 2013. A near-circumpolar flight was achieved with a duration of approximately two weeks. The flight performance of the Pathfinder design is discussed for the three Crab observations conducted. The signal-to-background ratio for the observations is shown to be 0.25 ±0.03 and the Minimum Detectable Polarisation (99 % C.L.) is (28.4 ±2.2) %. A strategy for the continuation of the PoGOLite programme is outlined based on experience gained during the 2013 maiden flight.
|
|
| 22. |
- Kawano, H., et al.
(författare)
-
Pi 2 waves simultaneously observed by Cluster and CPMN ground-based magnetometers near the plasmapause
- 2011
-
Ingår i: Annales Geophysicae. - : Copernicus GmbH. - 0992-7689 .- 1432-0576. ; 29:9, s. 1663-1672
-
Tidskriftsartikel (refereegranskat)abstract
- We have analyzed an event on 14 February 2003 in which Cluster satellites and the CPMN ground magnetometer chain made simultaneous observations of a Pi 2 pulsation along the same meridian. Three of the four Cluster satellites were located outside the plasmasphere, while the other one was located within the plasmasphere. By combining the multipoint observations in space and the multipoint observations on the ground, we have obtained a detailed L-profile of the Pi 2 signatures, which has not been done in the past. In addition, we have used a method called Independent Component Analysis (ICA) to separate out other superposed waves with similar spectral components. The result shows that the wave phase of the Pi 2 was the same up to L similar to 3.9 (corresponding to the plasmasphere), became earlier up to L similar to 4.1 (corresponding to the plasmapause boundary layer), and showed a delaying tendency up to L similar to 5.9 (corresponding to the plasmatrough). This systematic phase pattern, obtained for the first time by a combination of a ground magnetometer chain and multisatellites along a magnetic meridian with the aid of ICA, supports the interpretation that a Pi 2 signal propagated from a farther source and reached the plasmasphere.
|
|
| 23. |
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Cameron, A. S., et al.
(författare)
-
Probing superconducting order in overdoped Cax Y1-xBa2Cu3 O7 by neutron diffraction measurements of the vortex lattice
- 2023
-
Ingår i: Physical Review B. - 2469-9950. ; 108:14
-
Tidskriftsartikel (refereegranskat)abstract
- We present small-Angle neutron scattering studies of the magnetic vortex lattice (VL) in Ca0.04Y0.96Ba2Cu3O7 up to a field of 16.7 T and Ca0.15Y0.85Ba2Cu3O7 up to 25 T to investigate the general behavior of the superconducting gap in YBCO-based compounds at high magnetic field. We find in these overdoped compounds that the series of VL structure transitions have shifted down in field relative to those reported for the undoped compound. The hole doping by calcium is expected to alter the Fermi velocity and it reduces the upper critical field of the system. However, we attribute the VL changes mainly to the weakening of the 1D superconductivity in the Cu-O chains by the disorder introduced by doping. The high-field structure of the VL is similar to recent measurements on the parent compound in even higher fields of 25 T, which indicates that the fundamental d-wave nature of the superconducting gap is unchanged by calcium doping. This is corroborated by the temperature dependence of the VL form factor, which also shows the same d-wave behavior as observed in other cuprates. We also argue that they might be the explanation of Pauli paramagnetic effects in the field dependence of the VL form factor.
|
|
| 27. |
- Carlson, A. D., et al.
(författare)
-
A new evaluation of the neutron data standards
- 2017
-
Ingår i: ND 2016. - : EDP Sciences. - 9782759890200
-
Konferensbidrag (refereegranskat)abstract
- Evaluations are being done for the H(n,n), 6Li(n,t), 10B(n,αγ), 10B(n,α), C(n,n), Au(n,γ), 235U(n,f) and 238U(n,f) standard cross sections. Evaluations are also being done for data that are not traditional standards including: the Au(n,γ) cross section at energies below where it is considered a standard; reference cross sections for prompt gamma-ray production in fast neutron-induced reactions; reference cross sections for very high energy fission cross sections; the 235U thermal neutron fission spectrum and the 252Cf spontaneous fission neutron spectrum and the thermal constants.
|
|
| 28. |
- Chadwick, MB, et al.
(författare)
-
Open problems in quantum-mechanical approaches to multistep direct nuclear reactions
- 1999
-
Ingår i: ACTA PHYSICA SLOVACA. - : SLOVAK ACAD SCIENCES INST PHYSICS. - 0323-0465. ; 49:3, s. 365-379
-
Tidskriftsartikel (refereegranskat)abstract
- Open problems in the theoretical formulation and computational implementation of multistep direct preequilibrium reactions are discussed. Recommendations for future research on both theoretical and experimental aspects of the problem are given.
|
|
| 29. |
- Chauvin, Maxime, et al.
(författare)
-
Calibration and performance studies of the balloon-borne hard X-ray polarimeter PoGO
- 2017
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : ELSEVIER SCIENCE BV. - 0168-9002 .- 1872-9576. ; 859, s. 125-133
-
Tidskriftsartikel (refereegranskat)abstract
- Polarimetric observations of celestial sources in the hard X-ray band stand to provide new information on emission mechanisms and source geometries. PoGO+ is a Compton scattering polarimeter (20-150 keV) optimised for the observation of the Crab (pulsar and wind nebula) and Cygnus X-1 (black hole binary), from a stratospheric balloon-borne platform launched from the Esrange Space Centre in summer 2016. Prior to flight, the response of the polarimeter has been studied with polarised and unpolarised X-rays allowing a Geant4-based simulation model to be validated. The expected modulation factor for Crab observations is found to be M-Crab = (41.75 +/- 0.85)%, resulting in an expected Minimum Detectable Polarisation (MDP) of 7.3% for a 7 day flight. This will allow a measurement of the Crab polarisation parameters with at least 5 sigma statistical significance assuming a polarisation fraction similar to 20% - a significant improvement over the PoGOLite Pathfinder mission which flew in 2013 and from which the PoGO+ design is developed.
|
|
| 30. |
- Chauvin, Maxime, et al.
(författare)
-
Optimising a balloon-borne polarimeter in the hard X-ray domain : From the PoGOLite Pathfinder to PoGO
- 2016
-
Ingår i: Astroparticle physics. - : Elsevier. - 0927-6505 .- 1873-2852. ; 82, s. 99-107
-
Tidskriftsartikel (refereegranskat)abstract
- PoGOLite is a balloon-borne hard X-ray polarimeter dedicated to the study of point sources. Compton scattered events are registered using an array of plastic scintillator units to determine the polarisation of incident X-rays in the energy range 20-240 keV. In 2013, a near circumpolar balloon flight of 14 days duration was completed after launch from Esrange, Sweden, resulting in a measurement of the linear polarisation of the Crab emission. Building on the experience gained from this Pathfinder flight, the polarimeter is being modified to improve performance for a second flight in 2016. Such optimisations, based on Geant4 Monte Carlo simulations, take into account the source characteristics, the instrument response and the background environment which is dominated by atmospheric neutrons. This paper describes the optimisation of the polarimeter and details the associated increase in performance. The resulting design, PoGO+, is expected to improve the Minimum Detectable Polarisation (MDP) for the Crab from 19.8% to 11.1% for a 5 day flight. Assuming the same Crab polarisation fraction as measured during the 2013 flight, this improvement in MDP will allow a 5 sigma constrained result. It will also allow the study of the nebula emission only (Crab off-pulse) and Cygnus X-1 if in the hard state.
|
|
| 31. |
- Chauvin, Maxime, et al.
(författare)
-
Preflight performance studies of the PoGOLite hard X-ray polarimeter
- 2016
-
Ingår i: Astroparticle physics. - : Elsevier BV. - 0927-6505 .- 1873-2852. ; 72, s. 1-10
-
Tidskriftsartikel (refereegranskat)abstract
- Polarimetric studies of astrophysical sources can make important contributions to resolve the geometry of the emitting region and determine the photon emission mechanism. PoGOLite is a balloon-borne polarimeter operating in the hard X-ray band (25-240 key), with a Pathfinder mission focussing on Crab observations. Within the polarimeter, the distribution of Compton scattering angles is used to determine the polarisation fraction and angle of incident photons. To assure an unbiased measurement of the polarisation during a balloon flight it is crucial to characterise the performance of the instrument before the launch. This paper presents the results of the PoGOLite calibration tests and simulations performed before the 2013 balloon flight. The tests performed confirm that the polarimeter does not have any intrinsic asymmetries and therefore does not induce bias into the measurements. Generally, good agreement is found between results from test data and simulations which allows the polarimeter performance to be estimated for Crab observations.
|
|
| 32. |
|
|
| 33. |
- LeDuc, Richard D., et al.
(författare)
-
Proteomics Standards Initiative's ProForma 2.0 : Unifying the Encoding of Proteoforms and Peptidoforms br
- 2022
-
Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 21:4, s. 1189-1195
-
Tidskriftsartikel (refereegranskat)abstract
- It is important for the proteomics community to have a standardizedmanner to represent all possible variations of a protein or peptide primary sequence,including natural, chemically induced, and artifactual modifications. The HumanProteome Organization Proteomics Standards Initiative in collaboration with severalmembers of the Consortium for Top-Down Proteomics (CTDP) has developed astandard notation called ProForma 2.0, which is a substantial extension of the originalProForma notation developed by the CTDP. ProForma 2.0 aims to unify therepresentation of proteoforms and peptidoforms. ProForma 2.0 supports use casesneeded for bottom-up and middle-/top-down proteomics approaches and allows theencoding of highly modified proteins and peptides using a human- and machine-readable string. ProForma 2.0 can be used to represent protein modifications in a specified or ambiguous location, designated bymass shifts, chemical formulas, or controlled vocabulary terms, including cross-links (natural and chemical) and atomic isotopes.Notational conventions are based on public controlled vocabularies and ontologies. The most up-to-date full specification documentand information about software implementations are available athttp://psidev.info/proforma.
|
|
| 34. |
|
|
| 35. |
- Shigematsu-Locatelli, M., et al.
(författare)
-
Maternal pain during pregnancy dose-dependently predicts postpartum depression: The Japan Environment and Children's Study
- 2022
-
Ingår i: Journal of Affective Disorders. - : Elsevier BV. - 0165-0327. ; 303, s. 346-352
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Postpartum depression (PPD) affects women during the first year after delivery. This study investigated the association between prenatal pain (maternal pain during pregnancy) and PPD. Methods: Data were analyzed from the Japan Environment and Children's Study (JECS), a nationwide prospective birth cohort study. Information on prenatal pain was collected twice during pregnancy through self-administered questionnaires. PPD symptoms were assessed using the Edinburgh Postnatal Depression Scale at one month postpartum. Poisson regression analyses were performed to investigate the association between prenatal pain and PPD, with other putative risk factors adjusted in the model. Results: Among 84,801 study subjects, 11,535 (13.6%) were screened as positive for PPD. In the present study, the occurrence of prenatal pain was 69.6 and 84.0% at the first trimester and the second/third trimester, respectively. A positive relationship between any degree of pain and PPD in both the first and the second/third trimester was observed. A significant linear dose-dependent association was also found (Ptrend < 0.001) when the subjects were divided by the severity of pain. Using participants without any pain at either point as a reference, those with persistent pain both at the first and the second/third trimesters showed the highest risk for PPD: aRR = 1.95 (95%CI: 1.76–2.15; p < 0.001). Limitations: No detailed information regarding the type or site of prenatal pain was available in the JECS questionnaires, neither did data concerning delivery and postpartum pain. Conclusions: The study results suggest that prenatal pain is a dose-dependent risk factor for the development of PPD. © 2022 The Authors
|
|
| 36. |
|
|
