| 1. |
- Obers, Niels A., et al.
(författare)
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Quantum gravity phenomenology at the dawn of the multi-messenger era—A review
- 2022
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Ingår i: Progress in Particle and Nuclear Physics. - : Elsevier BV. - 0146-6410 .- 1873-2224. ; 125
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Forskningsöversikt (refereegranskat)abstract
- The exploration of the universe has recently entered a new era thanks to the multi-messenger paradigm, characterized by a continuous increase in the quantity and quality of experimental data that is obtained by the detection of the various cosmic messengers (photons, neutrinos, cosmic rays and gravitational waves) from numerous origins. They give us information about their sources in the universe and the properties of the intergalactic medium. Moreover, multi-messenger astronomy opens up the possibility to search for phenomenological signatures of quantum gravity. On the one hand, the most energetic events allow us to test our physical theories at energy regimes which are not directly accessible in accelerators; on the other hand, tiny effects in the propagation of very high energy particles could be amplified by cosmological distances. After decades of merely theoretical investigations, the possibility of obtaining phenomenological indications of Planck-scale effects is a revolutionary step in the quest for a quantum theory of gravity, but it requires cooperation between different communities of physicists (both theoretical and experimental). This review, prepared within the COST Action CA18108 “Quantum gravity phenomenology in the multi-messenger approach”, is aimed at promoting this cooperation by giving a state-of-the art account of the interdisciplinary expertise that is needed in the effective search of quantum gravity footprints in the production, propagation and detection of cosmic messengers.
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| 2. |
- Amati, L., et al.
(författare)
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The THESEUS space mission concept : science case, design and expected performances
- 2018
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Ingår i: Advances in Space Research. - : ELSEVIER SCI LTD. - 0273-1177 .- 1879-1948. ; 62:1, s. 191-244
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Tidskriftsartikel (refereegranskat)abstract
- THESEUS is a space mission concept aimed at exploiting Gamma-Ray Bursts for investigating the early Universe and at providing a substantial advancement of multi-messenger and time-domain astrophysics. These goals will be achieved through a unique combination of instruments allowing GRB and X-ray transient detection over a broad field of view (more than 1 sr) with 0.5-1 arcmin localization, an energy band extending from several MeV down to 0.3 keV and high sensitivity to transient sources in the soft X-ray domain, as well as on-board prompt (few minutes) follow-up with a 0.7 m class IR telescope with both imaging and spectroscopic capabilities. THESEUS will be perfectly suited for addressing the main open issues in cosmology such as, e.g., star formation rate and metallicity evolution of the inter-stellar and intra-galactic medium up to redshift similar to 10, signatures of Pop III stars, sources and physics of re-ionization, and the faint end of the galaxy luminosity function. In addition, it will provide unprecedented capability to monitor the X-ray variable sky, thus detecting, localizing, and identifying the electromagnetic counterparts to sources of gravitational radiation, which may be routinely detected in the late '20s/early '30s by next generation facilities like aLIGO/ aVirgo, eLISA, KAGRA, and Einstein Telescope. THESEUS will also provide powerful synergies with the next generation of multi-wavelength observatories (e.g., LSST, ELT, SKA, CTA, ATHENA).
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| 3. |
- Kasliwal, M. M., et al.
(författare)
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Illuminating gravitational waves : A concordant picture of photons from a neutron star merger
- 2017
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 358:6370, s. 1559-
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Tidskriftsartikel (refereegranskat)abstract
- Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.
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| 4. |
- Mooley, K., et al.
(författare)
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A mildly relativistic wide-angle outflow in the neutron-star merger event GW170817
- 2018
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 554:7691, s. 207-210
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Tidskriftsartikel (refereegranskat)abstract
- GW170817 was the first gravitational-wave detection of a binary neutron-star merger. It was accompanied by radiation across the electromagnetic spectrum and localized to the galaxy NGC 4993 at a distance of 40 megaparsecs. It has been proposed that the observed γ-ray, X-ray and radio emission is due to an ultra-relativistic jet being launched during the merger (and successfully breaking out of the surrounding material), directed away from our line of sight (off-axis). The presence of such a jet is predicted from models that posit neutron-star mergers as the drivers of short hard-γ-ray bursts. Here we report that the radio light curve of GW170817 has no direct signature of the afterglow of an off-axis jet. Although we cannot completely rule out the existence of a jet directed away from the line of sight, the observed γ-ray emission could not have originated from such a jet. Instead, the radio data require the existence of a mildly relativistic wide-angle outflow moving towards us. This outflow could be the high-velocity tail of the neutron-rich material that was ejected dynamically during the merger, or a cocoon of material that breaks out when a jet launched during the merger transfers its energy to the dynamical ejecta. Because the cocoon model explains the radio light curve of GW170817, as well as the γ-ray and X-ray emission (and possibly also the ultraviolet and optical emission), it is the model that is most consistent with the observational data. Cocoons may be a ubiquitous phenomenon produced in neutron-star mergers, giving rise to a hitherto unidentified population of radio, ultraviolet, X-ray and γ-ray transients in the local Universe.
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| 5. |
- Bejger, M., et al.
(författare)
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Collisional Penrose Process near the Horizon of Extreme Kerr Black Holes
- 2012
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 109:12
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Tidskriftsartikel (refereegranskat)abstract
- Collisions of particles in black hole ergospheres may result in an arbitrarily large center-of-mass energy. This led recently to the suggestion [M. Banados, J. Silk, and S. M. West, Phys. Rev. Lett. 103, 111102 (2009)] that black holes can act as ultimate particle accelerators. If the energy of an outgoing particle is larger than the total energy of the infalling particles, the energy excess must come from the rotational energy of the black hole and hence, a Penrose process is involved. However, while the center-of-mass energy diverges, the position of the collision makes it impossible for energetic particles to escape to infinity. Following an earlier work on collisional Penrose processes [T. Piran and J. Shaham, Phys. Rev. D 16, 1615 (1977)], we show that even under the most favorable idealized conditions the maximal energy of an escaping particle is only a modest factor above the total initial energy of the colliding particles. This implies that one should not expect collisions around a black hole to act as spectacular cosmic accelerators.
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| 6. |
- Englund, Martin, et al.
(författare)
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Incidental meniscal findings on knee MRI in middle-aged and elderly persons
- 2008
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Ingår i: New England Journal of Medicine. - 0028-4793. ; 359:11, s. 1108-1115
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Tidskriftsartikel (refereegranskat)abstract
- Background: Magnetic resonance imaging (MRI) of the knee is often performed in patients who have knee symptoms of unclear cause. When meniscal tears are found, it is commonly assumed that the symptoms are attributable to them. However, there is a paucity of data regarding the prevalence of meniscal damage in the general population and the association of meniscal tears with knee symptoms and with radiographic evidence of osteoarthritis. Methods: We studied persons from Framingham, Massachusetts, who were drawn from census-tract data and random-digit telephone dialing. Subjects were 50 to 90 years of age and ambulatory; selection was not made on the basis of knee or other joint problems. We assessed the integrity of the menisci in the right knee on 1.5-tesla MRI scans obtained from 991 subjects (57% of whom were women). Symptoms involving the right knee were evaluated by questionnaire. Results: The prevalence of a meniscal tear or of meniscal destruction in the right knee as detected on MRI ranged from 19% (95% confidence interval [CI], 15 to 24) among women 50 to 59 years of age to 56% (95% CI, 46 to 66) among men 70 to 90 years of age; prevalences were not materially lower when subjects who had had previous knee surgery were excluded. Among persons with radiographic evidence of osteoarthritis (Kellgren-Lawrence grade 2 or higher, on a scale of 0 to 4, with higher numbers indicating more definite signs of osteoarthritis), the prevalence of a meniscal tear was 63% among those with knee pain, aching, or stiffness on most days and 60% among those without these symptoms. The corresponding prevalences among persons without radiographic evidence of osteoarthritis were 32% and 23%. Sixty-one percent of the subjects who had meniscal tears in their knees had not had any pain, aching, or stiffness during the previous month. Conclusions: Incidental meniscal findings on MRI of the knee are common in the general population and increase with increasing age.
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| 7. |
- Englund, Martin, et al.
(författare)
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Meniscal Tear in Knees Without Surgery and the Development of Radiographic Osteoarthritis Among Middle-Aged and Elderly Persons The Multicenter Osteoarthritis Study
- 2009
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Ingår i: Arthritis and Rheumatism. - : Wiley. - 1529-0131 .- 0004-3591. ; 60:3, s. 831-839
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Tidskriftsartikel (refereegranskat)abstract
- Objective. Although partial meniscectomy is a risk factor for the development of knee osteoarthritis (OA), there is a lack of evidence that meniscal damage that is not treated with surgery would also lead to OA, suggesting that surgery itself may cause joint damage. Furthermore, meniscal damage is common. The aim of this study was to evaluate the association between meniscal damage in knees without surgery and the development of radiographic tibiofemoral OA. Methods. We conducted a prospective case-control study nested within the observational Multicenter Osteoarthritis Study, which included a sample of men and women ages 50-79 years at high risk of knee OA who were recruited from the community. Patients who had no baseline radiographic knee OA but in whom tibiofemoral OA developed during the 30-month followup period were cases (n = 121). Control subjects (n = 294) were drawn randomly from the same source population as cases but had no knee OA after 30 months of followup. Individuals whose knees had previously undergone surgery were excluded. Meniscal damage was defined as the presence of any medial or lateral meniscal tearing, maceration, or destruction. Results. Meniscal damage at baseline was more common in case knees than in control knees (54% versus 18%; P < 0.001). The model comparing any meniscal damage with no meniscal damage (adjusted for baseline age, sex, body mass index, physical activity, and mechanical knee alignment) yielded an odds ratio of 5.7 (95% confidence interval 3.4-9.4). Conclusion. In knees without surgery, meniscal damage is a potent risk factor for the development of radiographic OA. These results highlight the need for better understanding, prevention, and treatment of meniscal damage.
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| 8. |
- Felson, David T, et al.
(författare)
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Knee buckling: prevalence, risk factors, and associated limitations in function
- 2007
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Ingår i: Annals of Internal Medicine. - 0003-4819. ; 147:8, s. 534-540
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Knee buckling is common in persons with advanced knee osteoarthritis and after orthopedic procedures. Its prevalence in the community is unknown. OBJECTIVE: To examine the prevalence of knee buckling in the community, its associated risk factors, and its relation to functional limitation. DESIGN: Cross-sectional, population-based study. SETTING: The Framingham Osteoarthritis Study. PARTICIPANTS: 2351 men and women age 36 to 94 years (median, 63.5 years). MEASUREMENTS: Participants were asked whether they had experienced knee buckling or "giving way" and whether it led to falling. They were also asked about knee pain and limitations in function by using the Short Form-12 and Western Ontario and McMaster Universities Osteoarthritis Index, had isometric tests of quadriceps strength, and underwent weight-bearing radiography and magnetic resonance imaging of the knee. Radiographs were scored for osteoarthritis by using the Kellgren-Lawrence scale, and magnetic resonance images were read for anterior cruciate ligament tears. The relationship of buckling to functional limitation was examined by using logistic regression that adjusted for age, sex, body mass index, and knee pain severity. RESULTS: Two hundred seventy-eight participants (11.8%) experienced at least 1 episode of knee buckling within the past 3 months; of these persons, 217 (78.1%) experienced more than 1 episode and 35 (12.6%) fell during an episode. Buckling was independently associated with the presence of knee pain and with quadriceps weakness. Over half of those with buckling had no osteoarthritis on radiography. Persons with knee buckling had worse physical function than those without buckling, even after adjustment for severity of knee pain and weakness. For example, 46.9% of participants with buckling and 21.7% of those without buckling reported limitations in their work (adjusted odds ratio, 2.0 [95% CI, 1.5 to 2.7]). LIMITATION: Causal inferences are limited because of the study's cross-sectional design. CONCLUSION: In adults, knee buckling is common and is associated with functional loss.
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| 9. |
- Guermazi, Ali, et al.
(författare)
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Prevalence of abnormalities in knees detected by MRI in adults without knee osteoarthritis: population based observational study (Framingham Osteoarthritis Study)
- 2012
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Ingår i: BMJ: British Medical Journal. - : BMJ. - 1756-1833. ; 345, s. 5339-5339
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Tidskriftsartikel (refereegranskat)abstract
- Objective To examine use of magnetic resonance imaging (MRI) of knees with no radiographic evidence of osteoarthritis to determine the prevalence of structural lesions associated with osteoarthritis and their relation to age, sex, and obesity. Design Population based observational study. Setting Community cohort in Framingham, MA, United States (Framingham osteoarthritis study). Participants 710 people aged >50 who had no radiographic evidence of knee osteoarthritis (Kellgren-Lawrence grade 0) and who underwent MRI of the knee. Main outcome measures Prevalence of MRI findings that are suggestive of knee osteoarthritis (osteophytes, cartilage damage, bone marrow lesions, subchondral cysts, meniscal lesions, synovitis, attrition, and ligamentous lesions) in all participants and after stratification by age, sex, body mass index (BMI), and the presence or absence of knee pain. Pain was assessed by three different questions and also by WOMAC questionnaire. Results Of the 710 participants, 393 (55%) were women, 660 (93%) were white, and 206 (29%) had knee pain in the past month. The mean age was 62.3 years and mean BMI was 27.9. Prevalence of "any abnormality" was 89% (631/710) overall. Osteophytes were the most common abnormality among all participants (74%, 524/710), followed by cartilage damage (69%, 492/710) and bone marrow lesions (52%, 371/710). The higher the age, the higher the prevalence of all types of abnormalities detectable by MRI. There were no significant differences in the prevalence of any of the features between BMI groups. The prevalence of at least one type of pathology ("any abnormality") was high in both painful (90-97%, depending on pain definition) and painless (86-88%) knees. Conclusions MRI shows lesions in the tibiofemoral joint in most middle aged and elderly people in whom knee radiographs do not show any features of osteoarthritis, regardless of pain.
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| 10. |
- Haugen, Ida K., et al.
(författare)
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Prevalence, incidence and progression of hand osteoarthritis in the general population: the Framingham Osteoarthritis Study
- 2011
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Ingår i: Annals of the Rheumatic Diseases. - : BMJ. - 1468-2060 .- 0003-4967. ; 70:9, s. 1581-1586
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Tidskriftsartikel (refereegranskat)abstract
- Objectives To describe the prevalence and longitudinal course of radiographic, erosive and symptomatic hand osteoarthritis (HOA) in the general population. Methods Framingham osteoarthritis (OA) study participants obtained bilateral hand radiographs at baseline and 9-year follow-up. The authors defined radiographic HOA at joint level as Kellgren-Lawrence grade (KLG)>= 2, erosive HOA as KLG >= 2 plus erosion and symptomatic HOA as KLG >= 2 plus pain/aching/stiffness. Presence of HOA at individual level was defined as >= 1 affected joint. The prevalence was age-standardised (US 2000 Population 40-84 years). Results Mean (SD) baseline age was 58.9 (9.9) years (56.5% women). The age-standardised prevalence of HOA was only modestly higher in women (44.2%) than men (37.7%), whereas the age-standardised prevalence of erosive and symptomatic OA was much higher in women (9.9% vs 3.3%, and 15.9% vs 8.2%). The crude incidence of HOA over 9-year follow-up was similar in women (34.6%) and men (33.7%), whereas the majority of those women (96.4%) and men (91.4%) with HOA at baseline showed progression during follow-up. Incident metacarpophalangeal and wrist OA were rare, but occurred more frequently and from an earlier age in men than women. Development of erosive disease occurred mainly in those with non-erosive HOA at baseline (as opposed to those without HOA), and was more frequent in women (17.3%) than men (9.6%). Conclusions The usual female predominance of prevalent and incident HOA was less clear for radiographic HOA than for symptomatic and erosive HOA. With an ageing population, the impact of HOA will further increase.
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