We have measured parity-violating asymmetries in elastic electron-proton and quasielastic electron-deuteron scattering at Q2=0.22 and 0.63 GeV2. They are sensitive to strange quark contributions to ...currents in the nucleon and the nucleon axial-vector current. The results indicate strange quark contributions of approximately < 10% of the charge and magnetic nucleon form factors at these four-momentum transfers. We also present the first measurement of anapole moment effects in the axial-vector current at these four-momentum transfers.
We report on a new measurement of the beam transverse single spin asymmetry in electron-proton elastic scattering, A_{⊥}^{ep}, at five beam energies from 315.1 to 1508.4 MeV and at a scattering angle ...of 30°<θ<40°. The covered Q^{2} values are 0.032, 0.057, 0.082, 0.218, 0.613 (GeV/c)^{2}. The measurement clearly indicates significant inelastic contributions to the two-photon-exchange (TPE) amplitude in the low-Q^{2} kinematic region. No theoretical calculation is able to reproduce our result. Comparison with a calculation based on unitarity, which only takes into account elastic and πN inelastic intermediate states, suggests that there are other inelastic intermediate states such as ππN, KΛ, and ηN. Covering a wide energy range, our new high-precision data provide a benchmark to study those intermediate states.
New measurements of the beam normal single spin asymmetry in the electron elastic and quasielastic scattering on the proton and deuteron, respectively, at large backward angles and at ⟨Q^{2}⟩=0.22 ...(GeV/c)^{2} and ⟨Q^{2}⟩=0.35 ( GeV/c)^{2} are reported. The experimentally observed asymmetries are compared with the theoretical calculation of Pasquini and Vanderhaeghen Phys. Rev. C 70, 045206 (2004).PRVCAN0556-281310.1103/PhysRevC.70.045206. The agreement of the measurements with the theoretical calculations shows a dominance of the inelastic intermediate excited states of the nucleon, πN and the Δ resonance. The measurements explore a new, important parameter region of the exchanged virtual photon virtualities.
A new measurement of the parity violating asymmetry in elastic electron scattering on hydrogen at backward angles and at a four momentum transfer of Q;{2} = 0.22 (Ge V / c);{2} is reported here. The ...measured asymmetry is A_{LR} = (-17.23 +/- 0.82_{stat} +/- 0.89_{syst}) x 10;{-6}. The standard model prediction assuming no strangeness is A_{0} = (-15.87 +/- 1.22) x 10;{-6}. In combination with previous results from measurements at forward angles, it is possible to disentangle for the first time the strange form factors at this momentum transfer, G_{E};{s} = 0.050 +/- 0.038 +/- 0.019 and G_{M};{s} = -0.14 +/- 0.11 +/- 0.11.
Background
This study aims to determine the potential risk factors associated with the development of severe diving-related spinal cord decompression sickness (DCS).
Methods
Two hundred and seventy ...nine injured recreational divers (42 ± 12 years; 53 women) presenting symptoms of spinal cord DCS were retrospectively included from seven hyperbaric centers in France and Belgium. Diving information, symptom latency after surfacing, time interval between symptom onset and hyperbaric treatment were studied. The initial severity of spinal cord DCS was rated with the Boussuges severity score, and the presence of sequelae was evaluated at 1 month. Initial recompression treatment at 2.8 ATA with 100% oxygen breathing or deeper recompression up to 4 or 6 ATA with nitrogen or helium–oxygen breathing mixture were also recorded.
Results
Twenty six percent of DCS had incomplete resolution after 1 month. Multivariate analysis revealed several independent factors associated with a bad recovery: age ≥42 OR 1.04 (1–1.07), depth ≥39 m OR 1.04 (1–1.07), bladder dysfunction OR 3.8 (1.3–11.15), persistence or worsening of clinical symptoms before recompression OR 2.07 (1.23–3.48), and a Boussuges severity score >7 OR 1.16 (1.03–1.31). However, the time to recompression and the choice of initial hyperbaric procedure did not significantly influence recovery after statistical adjustment.
Conclusions
Clinical symptoms of spinal cord DCS and their initial course before admission to the hyperbaric center should be considered as major prognostic factors in recovery. A new severity score is proposed to optimize the initial clinical evaluation for spinal cord DCS.
We report on a measurement of the parity-violating asymmetry in the scattering of longitudinally polarized electrons on unpolarized protons at a Q2 of 0.230 (GeV/c)(2) and a scattering angle of theta ...(e) = 30 degrees - 40 degrees. Using a large acceptance fast PbF2 calorimeter with a solid angle of delta omega = 0.62 sr, the A4 experiment is the first parity violation experiment to count individual scattering events. The measured asymmetry is A(phys)=(-5.44+/-0.54(stat)+/-0.26(sys))x10(-6). The standard model expectation assuming no strangeness contributions to the vector form factors is A(0) = (-6.30+/-0.43) x 10(-6). The difference is a direct measurement of the strangeness contribution to the vector form factors of the proton. The extracted value is G(s)(E) + 0.225G(s)(M) = 0.039+/-0.034 or F(s)(1) + 0.130F(s)(2) = 0.032+/-0.028.
A new measurement of the parity-violating asymmetry in the electron-deuteron quasielastic scattering for backward angles at ⟨Q2⟩=0.224 (GeV/c)2, obtained in the A4 experiment at the Mainz Microtron ...accelerator (MAMI) facility, is presented. The measured asymmetry is APVd=(−20.11±0.87stat±1.03sys)×10−6. A combination of these data with the proton measurements of the parity-violating asymmetry in the A4 experiment yields a value for the effective isovector axial-vector form factor of GAe,(T=1)=−0.19±0.43 and RA(T=1),anap=−0.41±0.35 for the anapole radiative correction. When combined with a reanalysis of measurements obtained in the G0 experiment at the Thomas Jefferson National Accelerator Facility, the uncertainties are further reduced to GMs=0.17±0.11 for the magnetic strange form factors, and RA(T=1),anap=−0.54±0.26.
We report the case of a healthy 21-year-old woman who performed iterative breath-hold dives in relatively cold water, not exceeding depths of 5 meters but with "empty lungs." At the end of a dive, ...after experiencing an intense involuntary diaphragmatic contraction underwater, she presented hemoptysis followed by chest pain and cough. Chest radiography and computed tomography were performed 24 hours later, confirming the diagnosis of pneumomediastinum. The clinical course was benign: However, chest pain and effort dyspnea lasted for a few weeks. The pathophysiology of this accident may be explained by a combination of mechanisms involved in several clinical entities, namely pulmonary edema of immersion, pulmonary barotrauma and spontaneous pneumomediastinum.
Pulmonary edema occurring in divers using a self-contained underwater breathing apparatus (scuba) is an uncommon, probably under-reported, but potentially life-threatening and recurrent condition. We ...report six episodes of pulmonary edema in five scuba divers seen during a period of 15 months. The four men and one woman ranged in age from 37 to 56 years and two were treated for hypertension. Symptoms were mostly dyspnea onset at depth, cough, hemoptysis and hypoxemia, which in the recurrent case led to cardiac arrest and death. All cases occurred in rather cold water. Findings on thoracic computed tomography (CT) scanning ranged from pleural effusion to ground-glass opacities restricted to a few areas of the lung. The complex underlying mechanisms that would contribute to a raised transalveolar pressure or to a disruption of the blood-gas barrier are discussed. It is important for emergency care providers to be aware of this syndrome for prompt recognition and optimal treatment.
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