Differential cross sections for Compton scattering from the proton have been measured at scattering angles of 55°, 90°, and 125° in the laboratory frame using quasimonoenergetic linearly (circularly) ...polarized photon beams with a weighted mean energy value of 83.4 MeV (81.3 MeV). These measurements were performed at the High Intensity Gamma-Ray Source facility at the Triangle Universities Nuclear Laboratory. The results are compared to previous measurements and are interpreted in the chiral effective field theory framework to extract the electromagnetic dipole polarizabilities of the proton, which gives α_{E1}^{p}=13.8±1.2_{stat}±0.1_{BSR}±0.3_{theo},β_{M1}^{p}=0.2∓1.2_{stat}±0.1_{BSR}∓0.3_{theo} in units of 10^{-4} fm^{3}.
In this article, we analyze the impacts of climate change on Antarctic marine ecosystems. Observations demonstrate large-scale changes in the physical variables and circulation of the Southern Ocean ...driven by warming, stratospheric ozone depletion, and a positive Southern Annular Mode. Alterations in the physical environment are driving change through all levels of Antarctic marine food webs, which differ regionally. The distributions of key species, such as Antarctic krill, are also changing. Differential responses among predators reflect differences in species ecology. The impacts of climate change on Antarctic biodiversity will likely vary for different communities and depend on species range. Coastal communities and those of sub-Antarctic islands, especially range-restricted endemic communities, will likely suffer the greatest negative consequences of climate change. Simultaneously, ecosystem services in the Southern Ocean will likely increase. Such decoupling of ecosystem services and endemic species will require consideration in the management of human activities such as fishing in Antarctic marine ecosystems.
The reactions γp→ηp and γp→η^{'}p are measured from their thresholds up to the center-of-mass energy W=1.96 GeV with the tagged-photon facilities at the Mainz Microtron, MAMI. Differential cross ...sections are obtained with unprecedented statistical accuracy, providing fine energy binning and full production-angle coverage. A strong cusp is observed in the total cross section for η photoproduction at the energies in the vicinity of the η^{'} threshold, W=1896 MeV (E_{γ}=1447 MeV). Within the framework of a revised ηMAID isobar model, the cusp, in connection with a steep rise of the η^{'} total cross section from its threshold, can only be explained by a strong coupling of the poorly known N(1895)1/2^{-} state to both ηp and η^{'}p. Including the new high-accuracy results in the ηMAID fit to available η and η^{'} photoproduction data allows the determination of the N(1895)1/2^{-} properties.
The double polarization observable E and the helicity dependent cross sections σ_{1/2} and σ_{3/2} were measured for η photoproduction from quasifree protons and neutrons. The circularly polarized ...tagged photon beam of the A2 experiment at the Mainz MAMI accelerator was used in combination with a longitudinally polarized deuterated butanol target. The almost 4π detector setup of the Crystal Ball and TAPS is ideally suited to detect the recoil nucleons and the decay photons from η→2γ and η→3π^{0}. The results show that the narrow structure previously observed in η photoproduction from the neutron is only apparent in σ_{1/2} and hence, most likely related to a spin-1/2 amplitude. Nucleon resonances that contribute to this partial wave in η production are only N 1/2^{-} (S_{11}) and N 1/2^{+} (P_{11}). Furthermore, the extracted Legendre coefficients of the angular distributions for σ_{1/2} are in good agreement with recent reaction model predictions assuming a narrow resonance in the P_{11} wave as the origin of this structure.
The Proton Radius Puzzle Downie, E. J.
EPJ Web of Conferences,
01/2016, Letnik:
113
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The proton radius puzzle is the difference between the proton radius as measured with electron scattering and in the excitation spectrum of atomic hydrogen, and that measured with muonic hydrogen ...spectroscopy. Since the inception of the proton radius puzzle in 2010 by the measurement of Pohl et al.1, many possible resolutions to the puzzle have been postulated, but, to date, none has been generally accepted. New data are therefore necessary to resolve the issue. We briefly review the puzzle, the proposed solutions, and the new electron scattering and spectroscopy experiments planned and underway. We then introduce the MUSE experiment, which seeks to resolve the puzzle by simultaneously measuring elastic electron and muon scattering on the proton, in both charge states, thereby providing new information to the puzzle. MUSE addresses issues of two-photon effects, lepton universality and, possibly, new physics, while providing simultaneous form factor, and therefore radius, measurements with both muons and electrons.
Aims The aims of this study were to describe the temporal pattern of plasma N-terminal pro-brain natriuretic peptide, to examine the optimum time of sampling and to compare plasma N-terminal ...pro-brain natriuretic peptide to clinical criteria in terms of identification of impaired left ventricular systolic function following acute myocardial infarction. Methods and Results Measurements of N-terminal pro-brain natriuretic peptide were made in 60 patients at 14–48h, 49–72h, 73–120h, 121–192h following myocardial infarction and at 6 weeks in survivors. Left ventricular wall motion index was assessed during hospitalization (WMI-1) and at 6 weeks (WMI-2). N-terminal pro-brain natriuretic peptide levels were elevated at all time points, to a greater extent in anterior compared to inferior infarction (P<0·05). A biphasic profile of plasma concentration was observed in anterior infarction with peaks at 14–48h and 121–192h. This was sustained at 6 weeks. N-terminal pro- brain natriuretic peptide at 73–120h was the best independent predictor of WMI-1 (P<0·005). N-terminal pro-brain natriuretic peptide was higher at all times in patients who received ACE inhibitor therapy compared to those who did not (P<0·005). N-terminal pro-brain natriuretic peptide at 73–120h (R2=17·7%, P=0·005) and previous myocardial infarction (R2=5·3%, P<0·05) were independent predictors of poor outcome (WMI-2 ≤1·2 or death by 6 weeks). Conclusions A biphasic pattern of plasma N-terminal pro-brain natriuretic peptide is seen after anterior myocardial infarction. Plasma level is strongly correlated to wall motion index soon after and remote from acute myocardial infarction. Plasma N-terminal pro-brain natriuretic peptide measured later in hospitalization better predicts poor outcome following myocardial infarction than when it is measured in the immediate post infarction period.
•Pain and fatigue are prevalent among adult survivors of childhood cancer.•Survivors often have unmet needs for information about managing pain and fatigue.•Unmet needs are related to fear of cancer ...recurrence.
Pain and fatigue are under-researched late effects of childhood cancer and its treatment, and may be interpreted by survivors as indicating cancer recurrence. Moreover, unmet information needs for managing pain and fatigue may be related to fear of cancer recurrence. We investigated the complex relationships between perceived cancer-related pain and fatigue, unmet information needs for managing pain and fatigue, and fear of cancer recurrence.
We surveyed 404 adult survivors of any form of childhood cancer (M = 16.82 years since treatment completion).
Many survivors reported perceived cancer-related pain (28.7%) and fatigue (40.3%), and anticipated future pain (19.3%) and fatigue (26.2%). These symptomologies were all related to unmet information needs for managing pain (18.8%) and fatigue (32.2%; all p’s<.001). Survivors reporting unmet information needs for managing pain (B = .48, 95% CI = 0.19-0.76, p = .001) and fatigue (B = .32, 95% CI = 0.06-0.52, p = .015) reported higher fear of cancer recurrence than survivors reporting no information needs.
Survivors often have unmet information needs for managing pain and fatigue, and these unmet needs are related to fear of cancer recurrence.
Long-term follow-up clinics should assess pain and fatigue. Information provision about pain and fatigue may be an important tool to help manage fear of cancer recurrence.
The double-polarization observable E and helicity-dependent cross sections σ1/2, σ3/2 have been measured for the photoproduction of π0 pairs off quasifree protons and neutrons at the Mainz MAMI ...accelerator with the Crystal Ball/TAPS setup. A circularly polarized photon beam was produced by bremsstrahlung from longitudinally polarized electrons and impinged on a longitudinally polarized deuterated butanol target. The reaction products were detected with an almost 4π covering calorimeter. The results reveal for the first time the helicity- and isospin-dependent structure of the γN → Nπ0π0 reaction.They are compared to predictions from reaction models in view of nucleon resonance contributions and also to a refit of one model that predicted results for the proton and for the neutron target. As a result, the comparison of the prediction and the refit demonstrates the large impact of the new data.
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