| 1371. |
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| 1372. |
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| 1373. |
- Bott, Lukas Thomas, et al.
(författare)
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Coulomb dissociation of O-16 into He-4 and C-12
- 2023
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Ingår i: NUCLEAR PHYSICS IN ASTROPHYSICS - X, NPA-X 2022. - : EDP Sciences. - 2100-014X. ; 279
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Konferensbidrag (refereegranskat)abstract
- We measured the Coulomb dissociation of O-16 into He-4 and C-12 within the FAIR Phase-0 program at GSI Helmholtzzentrum fur Schwerionenforschung Darmstadt, Germany. From this we will extract the photon dissociation cross section O-16(alpha,gamma)C-12, which is the time reversed reaction to C-12(alpha,gamma)O-16. With this indirect method, we aim to improve on the accuracy of the experimental data at lower energies than measured so far. The expected low cross section for the Coulomb dissociation reaction and close magnetic rigidity of beam and fragments demand a high precision measurement. Hence, new detector systems were built and radical changes to the (RB)-B-3 setup were necessary to cope with the high-intensity O-16 beam. All tracking detectors were designed to let the unreacted O-16 ions pass, while detecting the C-12 and He-4.
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| 1374. |
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| 1375. |
- Broderick, Avery E., et al.
(författare)
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The Photon Ring in M87*
- 2022
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 1538-4357 .- 0004-637X. ; 935:1
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Tidskriftsartikel (refereegranskat)abstract
- We report measurements of the gravitationally lensed secondary image—the first in an infinite series of so-called “photon rings”—around the supermassive black hole M87* via simultaneous modeling and imaging of the 2017 Event Horizon Telescope (EHT) observations. The inferred ring size remains constant across the seven days of the 2017 EHT observing campaign and is consistent with theoretical expectations, providing clear evidence that such measurements probe spacetime and a striking confirmation of the models underlying the first set of EHT results. The residual diffuse emission evolves on timescales comparable to one week. We are able to detect with high significance a southwestern extension consistent with that expected from the base of a jet that is rapidly rotating in the clockwise direction. This result adds further support to the identification of the jet in M87* with a black hole spin-driven outflow, launched via the Blandford-Znajek process. We present three revised estimates for the mass of M87* based on identifying the modeled thin ring component with the bright ringlike features seen in simulated images, one of which is only weakly sensitive to the astrophysics of the emission region. All three estimates agree with each other and previously reported values. Our strongest mass constraint combines information from both the ring and the diffuse emission region, which together imply a mass-to-distance ratio of 4.20 − 0.06 + 0.12 μ as and a corresponding black hole mass of (7.13 ± 0.39) × 109 M ⊙, where the error on the latter is now dominated by the systematic uncertainty arising from the uncertain distance to M87*.
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| 1376. |
- Butt, Julia, et al.
(författare)
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Antibody Responses to Helicobacter pylori and Risk of Developing Colorectal Cancer in a European Cohort
- 2020
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Ingår i: Cancer Epidemiology, Biomarkers and Prevention. - : American Association for Cancer Research. - 1055-9965 .- 1538-7755. ; 29:7, s. 1475-1481
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Tidskriftsartikel (refereegranskat)abstract
- Background: While Helicobacter pylori (H. pylori) is the major cause of gastric cancer, it has also been suggested to be involved in colorectal cancer development. However, prospective studies addressing H. pylori and colorectal cancer are sparse and inconclusive. We assessed the association of antibody responses to H. pylori proteins with colorectal cancer in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort.Methods: We applied H. pylori multiplex serology to measure antibody responses to 13 H. pylori proteins in prediagnostic serum samples from 485 colorectal cancer cases and 485 matched controls nested within the EPIC study. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using multivariable conditional logistic regression to estimate the association of H. pylori overall and protein-specific seropositivity with odds of developing colorectal cancer.Results: Fifty-one percent of colorectal cancer cases were H. pylori seropositive compared with 44% of controls, resulting in an OR of 1.36 (95% CI, 1.00-1.85). Among the 13 individual H. pylori proteins, the association was driven mostly by seropositivity to Helicobacter cysteine-rich protein C (HcpC; OR: 1.66; 95% CI, 1.19-2.30) and Vacuolating cytotoxin A (VacA) (OR: 1.34; 95% CI, 0.99-1.82), the latter being nonstatistically significant only in the fully adjusted model.Conclusions: In this prospective multicenter European study, antibody responses to H. pylori proteins, specifically HcpC and VacA, were associated with an increased risk of developing colorectal cancer. Impact: Biological mechanisms for a potential causal role of H. pylori in colorectal carcinogenesis need to be elucidated, and subsequently whether H. pylori eradication may decrease colorectal cancer incidence.
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| 1377. |
- Buttery, R. J., et al.
(författare)
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The Impact of 3-D Fields on Tearing Mode Stability of H-modes
- 2011
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Ingår i: Nuclear Fusion. - 1741-4326 .- 0029-5515. ; 51, s. 073016-
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Tidskriftsartikel (refereegranskat)abstract
- New processes have been discovered in the interaction of 3D fields with tearing mode stability at low torque and modest β on DIII-D and NSTX. These are thought to arise from the plasma response at the tearing resonant surface, which theoretically is expected to depend strongly on plasma rotation and underlying intrinsic tearing stability. This leads to sensitivities additional to those previously identified at low density where the plasma rotation is more readily stopped, or at high βN where ideal MHD responses amplify the fields (where βN is the plasma β divided by the ratio of plasma current to minor radius multiplied by toroidal field). It is found that the threshold size for 3D fields to induce modes tends to zero as the natural tearing βN limit is approached. 3D field sensitivity is further enhanced at low rotation, with magnetic probing detecting an increased response to applied fields in such regimes. Modelling with the MARS-F code confirms the interpretation with the usual plasma screening response breaking down in low rotation plasmas and a tearing response developing, opening the door to additional sensitivities to β and the current profile. Typical field thresholds to induce modes in torque-free βN ~ 1.5 H-modes are well below those in ohmic plasmas or plasmas near the ideal βN limit. The strong interaction with the tearing mode βN limit is identified through rotation shear, which is decreased by the 3D field, leading to decreased tearing stability. Thus both locked and rotating mode field thresholds can be considered in terms of a torque balance, with sufficient braking leading to destabilization of a mode. On this basis new measurements of the principal parameter scalings for error field threshold have been obtained in torque-free H-modes leading to new predictions for error field sensitivity in ITER. The scalings have similar exponents to ohmic plasmas, but with seven times lower threshold at the ITER baseline βN value of 1.8, and a linear dependence on proximity to the tearing mode βN limit (~2.2 at zero torque). This reinforces the need to optimize error field correction strategies in ITER, and implement sources to drive plasma rotation.
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| 1378. |
- Cabanelas, P., et al.
(författare)
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Performance recovery of long CsI(Tl) scintillator crystals with APD-based readout
- 2020
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 965
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Tidskriftsartikel (refereegranskat)abstract
- CALIFA is the high efficiency and energy resolution calorimeter for the R3B experiment at FAIR, intended for detecting high energy light charged particles and gamma rays in scattering experiments, and is being commissioned during the Phase-0 experiments at FAIR, between 2018 and 2020. It surrounds the reaction target in a segmented configuration with 2432 detection units made of long CsI(Tl) finger-shaped scintillator crystals. CALIFA has a 10 year intended operational lifetime as the R3B calorimeter, necessitating measures to be taken to ensure enduring performance. In this paper we present a systematic study of two groups of 6 different detection units of the CALIFA detector after more than four years of operation. The energy resolution and light output yield are evaluated under different conditions. Tests cover the aging of the first detector units assembled and investigates recovery procedures for degraded detection units. A possible reason for the observed degradation is given, pointing to the crystal-APD coupling.
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| 1379. |
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| 1380. |
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