Increase in |S_L| induced by channel coupling: the case of deuteron scattering

For deuteron scattering from 58Ni at laboratory energies of 56, 79, and 120 MeV, we study the dynamic polarization potentials (DPPs) induced by S-wave and D-wave breakup (BU), separately and together, in order to gain insight into the nature of the DPP as well as a counterintuitive property: the existence of L values for which the BU coupling increases |SL|, a ‘wrong-way’ effect. The effect is associated with the existence of emissive regions in the imaginary DPP, suggesting a connection with the nonlocal nature of the DPP. The same relationship was previously found for 6Li scattering, indicating a generic effect bearing on the dynamics of nuclear reactions

Elastic scattering and breakup reactions of the proton drip-line nucleus 8 B on 208 Pb at 238 MeV

Elastic scattering and breakup angular distributions of the weakly bound radioactive nucleus 8 B on a 208Pb target at an incident energy of 238 MeV, which corresponds to four times the Coulomb barrier, have been measured at the HIRFL-RIBLL facility (Institute of Modern Physics, Lanzhou). The data have been analyzed using the optical model and the continuum discretized coupled channels (CDCC) formalism. The measured and calculated elastic scattering angular distributions do not show any significant Coulomb rainbow suppression. The angular distribution for the breakup reaction was measured for the first time at this energy. The angular distribution of the 7 Be fragments could be reproduced considering elastic plus nonelastic breakup contributions, with the former evaluated with the CDCC calculations and the latter with the model of Ichimura, Austern, and Vincent [Phys. Rev. C 32, 431 (1985)]. The comparison of the breakup cross section of 8 B with that of 11Be suggests that the Coulomb and centrifugal barriers encountered by the valence proton may suppress the breakup cross section.Fundación Nacional Programa clave de I + D de China (Subvención No. 2018YFA0404403)Fundación Nacional de Ciencias Naturales de China (Subvenciones No. 11947203, No. 11775013, No. 11575256 y No. U1632138)Youth Innovation Promotion Association CAS de China (No. 2020411)Fundación de Investigación de São Paulo (FAPESP) (Becas No. 2016/17612-7 y No. 2018/04965-4)Ministerio español de Ciencia, Innovación y Universidades (incluyendo FEDER fondos) bajo el proyecto FIS2017-88410-PUnión Europea programa de investigación e innovación Horizonte 2020 de la Unión Acuerdo de Subvención No. 654002

Elastic Scattering Phenomenology

We argue that, in many situations, fits to elastic scattering data that were historically, and frequently still are, considered “good”, are not justifiably so describable. Information about the dynamics of nucleon-nucleus and nucleus-nucleus scattering is lost when elastic scattering phenomenology is insufficiently ambitious. It is argued that in many situations, an alternative approach is appropriate for the phenomenology of nuclear elastic scattering of nucleons and other light nuclei. The approach affords an appropriate means of evaluating folding models, one that fully exploits available empirical data. It is particularly applicable for nucleons and other light ions

Scattering of the halo nucleus 11Be from a lead target at 3.5 times the Coulomb barrier energy

Angular distributions of quasielastic scattering and breakup of the neutron-rich halo nucleus 11Be on a 208Pb target at an incident energy of 140 MeV (about 3.5 times the Coulomb barrier) were measured at HIRFL-RIBLL. A strong suppression of the Coulomb nuclear interference peak is observed in the measured quasielastic scattering angular distribution. The result demonstrates for the first time the persistence of the strong breakup coupling effect reported so far for reaction systems involving neutron-halo nuclei at this relatively high incident energy. The measured quasielastic scattering cross sections are satisfactorily reproduced by continuum discretized coupled channel (CDCC) calculations as well as by the XCDCC calculations where the deformation of the 10Be core is taken into account. The angular and energy distributions of the 10Be fragments could also be well reproduced considering elastic breakup (CDCC and XCDCC) plus nonelastic breakup contributions, with the latter evaluated with the model by Ichimura, Austern and Vincent [1]. The comparison of the 10Be energy distributions with simple kinematical estimates evidence the presence of a significant post-acceleration effect which, in the (X)CDCC frameworks, is accounted for by continuum-continuum couplings.National Key Research and Development Program of China (Grant No. 2018YFA0404403)National Natural Science Foundation of China (Grant No. 11775013, No. 11947203, No. 11575256, and No. U1632138)Youth Innovation Promotion Association CAS (No. 2020411)Ministerio de Ciencia, Innovación y Universidades FIS2017-88410-PEuropean Union’s Horizon 2020 (Grant Agreement No. 654002

Spectroscopy of 18^{18}Na: Bridging the two-proton radioactivity of 19^{19}Mg

The unbound nucleus $^{18}$Na, the intermediate nucleus in the two-proton radioactivity of $^{19}$Mg, was studied by the measurement of the resonant elastic scattering reaction $^{17}$Ne(p,$^{17}$Ne)p performed at 4 A.MeV. Spectroscopic properties of the low-lying states were obtained in a R-matrix analysis of the excitation function. Using these new results, we show that the lifetime of the $^{19}$Mg radioactivity can be understood assuming a sequential emission of two protons via low energy tails of $^{18}$Na resonances

Search for gravitational-wave transients associated with magnetar bursts in advanced LIGO and advanced Virgo data from the third observing run

Gravitational waves are expected to be produced from neutron star oscillations associated with magnetar giant f lares and short bursts. We present the results of a search for short-duration (milliseconds to seconds) and longduration (∼100 s) transient gravitational waves from 13 magnetar short bursts observed during Advanced LIGO, Advanced Virgo, and KAGRA’s third observation run. These 13 bursts come from two magnetars, SGR1935 +2154 and SwiftJ1818.0−1607. We also include three other electromagnetic burst events detected by FermiGBM which were identified as likely coming from one or more magnetars, but they have no association with a known magnetar. No magnetar giant flares were detected during the analysis period. We find no evidence of gravitational waves associated with any of these 16 bursts. We place upper limits on the rms of the integrated incident gravitational-wave strain that reach 3.6 × 10−²³ Hz at 100 Hz for the short-duration search and 1.1 ×10−²² Hz at 450 Hz for the long-duration search. For a ringdown signal at 1590 Hz targeted by the short-duration search the limit is set to 2.3 × 10−²² Hz. Using the estimated distance to each magnetar, we derive upper limits upper limits on the emitted gravitational-wave energy of 1.5 × 1044 erg (1.0 × 1044 erg) for SGR 1935+2154 and 9.4 × 10^43 erg (1.3 × 1044 erg) for Swift J1818.0−1607, for the short-duration (long-duration) search. Assuming isotropic emission of electromagnetic radiation of the burst fluences, we constrain the ratio of gravitational-wave energy to electromagnetic energy for bursts from SGR 1935+2154 with the available fluence information. The lowest of these ratios is 4.5 × 103

What you need to know - Objective assessment of nasal patency - Why it is important

Singapore Medical Journal403186-187SIMJ

Modeling of turbulent transport and solidification during continuous ingot casting

Continuous ingot casting is an important processing technology for many materials. Under most practical circumstances, turbulence plays a critical role which, along with transport mechanisms such as buoyancy, surface tension, and phase change, is responsible for the quality of the end products. A modified turbulence model based on the standard k-e two-equation closure is proposed and applied to predict the phase change and convection-diffusion characteristics during titanium alloy ingot casting in an electron beam melting process. In conjunction with an adaptive grid computational technique, solutions of the coupled mass continuity, momentum, energy, and turbulence transport have been obtained in the context of the enthalpy formulation. Effects of casting speed and gravity on solidification and convection characteristics have been investigated and compared to ones obtained previously with a simple zeroequation turbulence model. The present turbulence model predicts that the mushy zone is generally of substantial thickness as a result of the convection effect, that the solidus line has a high curvature, and that the temperature gradient close to the solidus line is higher than elsewhere. Under all conditions, the turbulence structure largely reflects the combined influence of convection and energy input by the electron beam and the superheated feeding material from the top surface. The numerical results have been compared with an experimentally determined pool profile from a casting ingot. © 1992

Effect of turbulent heat transfer on continuous ingot solidification

For many continuous ingot casting processes, turbulent heat transfer in the molten pool plays a critical role which, along with buoyancy and surface tension, is responsible for the quality of the end products. Based on a modified low Reynolds number k-ε two-equation closure, accounting for the phase change and mushy zone formation, the effect of turbulent heat transfer on the solidification characteristics during titanium alloy ingot casting in an electron beam melting process is investigated. The overall heat transfer rate is enhanced by turbulent transport via two sources, one through the correlated velocity and temperature fluctuations present for both single- and multi-phase flows, and the other through the correlated velocity and release of latent heat fluctuations which are unique to the flows with phase change. The roles played by both mechanisms are identified and assessed. The present turbulence model predicts that although the mushy zone defined by the mean temperature field is generally of substantial thickness as a result of the convection effect, the actual instantaneous zone thickness varies substantially due to turbulence effect. This finding is in contrast to the traditionally held viewpoint, based on the conduction analysis, of a generally thin mushy zone. The impact of turbulent heat transfer on local dendrite formation and remelting is illustrated and the issues involved in model development highlighted