Sensitivity studies for r-process nucleosynthesis in three astrophysical scenarios

In rapid neutron capture, or r-process, nucleosynthesis, heavy elements are built up via a sequence of neutron captures and beta decays that involves thousands of nuclei far from stability. Though we understand the basics of how the r-process proceeds, its astrophysical site is still not conclusively known. The nuclear network simulations we use to test potential astrophysical scenarios require nuclear physics data (masses, beta decay lifetimes, neutron capture rates, fission probabilities) for all of the nuclei on the neutron-rich side of the nuclear chart, from the valley of stability to the neutron drip line. Here we discuss recent sensitivity studies that aim to determine which individual pieces of nuclear data are the most crucial for r-process calculations. We consider three types of astrophysical scenarios: a traditional hot r-process, a cold r-process in which the temperature and density drop rapidly, and a neutron star merger trajectory.Comment: 8 pages, 4 figures, submitted to the Proceedings of the International Nuclear Physics Conference (INPC) 201

Fission Cycling in a Supernova r-process

Recent halo star abundance observations exhibit an important feature of consequence to the r-process: the presence of a main r-process between the second and third peaks which is consistent among halo stars. We explore fission cycling and steady-beta flow as the driving mechanisms behind this feature. The presence of fission cycling during the r-process can account for nucleosynthesis yields between the second and third peaks, whereas the presence of steady-beta flow can account for consistent r-process patterns, robust under small variations in astrophysical conditions. We employ the neutrino-driven wind of the core-collapse supernova to examine fission cycling and steady-beta flow in the r-process. As the traditional neutrino-driven wind model does not produce the required very neutron-rich conditions for these mechanisms, we examine changes to the neutrino physics necessary for fission cycling to occur in the neutrino-driven wind environment, and we explore under what conditions steady-beta flow is obtained.Comment: 9 pages, 8 figure

The influence of collective neutrino oscillations on a supernova r-process

Recently, it has been demonstrated that neutrinos in a supernova oscillate collectively. This process occurs much deeper than the conventional matter-induced MSW effect and hence may have an impact on nucleosynthesis. In this paper we explore the effects of collective neutrino oscillations on the r-process, using representative late-time neutrino spectra and outflow models. We find that accurate modeling of the collective oscillations is essential for this analysis. As an illustration, the often-used "single-angle" approximation makes grossly inaccurate predictions for the yields in our setup. With the proper multiangle treatment, the effect of the oscillations is found to be less dramatic, but still significant. Since the oscillation patterns are sensitive to the details of the emitted fluxes and the sign of the neutrino mass hierarchy, so are the r-process yields. The magnitude of the effect also depends sensitively on the astrophysical conditions - in particular on the interplay between the time when nuclei begin to exist in significant numbers and the time when the collective oscillation begins. A more definitive understanding of the astrophysical conditions, and accurate modeling of the collective oscillations for those conditions, is necessary.Comment: 27 pages, 10 figure

Neutrino capture by r-process waiting-point nuclei

We use the Quasiparticle Random Phase Approximation to include the effects of low-lying Gamow-Teller and first forbidden strength in neutrino capture by very neutron-rich nuclei with N = 50, 82, or 126. For electron neutrinos in what is currently considered the most likely r-process site the capture cross sections are two or more times previous estimates. We briefly discuss the reliability of our calculations and their implications for nucleosynthesis.Comment: 9 pages, 4 figure

Development of a stability-indicating UPLC method for determination of isotretinoin in bulk drug

A highly sensitive and rapid stability indicating ultra-performance liquid chromatographic (UPLC) method was developed for the quantification and identification of isotretinoin in bulk. Chromatographic separation was developed using a gradient elution in a reversed-phase system at flow rate of 0.5 ml/min with 12 min run time. The mobile phase was a gradient mixture of mobile phase A (contained a 30:70:0.5 mixture solution of methanol/purified water/glacial acetic acid) and mobile phase B (contained a 70:25:4.5:0.5 mixture solution of methanol/acetonitrile/purified water/glacial acetic acid). Eluents were monitored at 355 nm. The analytical method was validated for accuracy, precision, robustness, linearity, and forced degradation in accordance with the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) topic Q2 (R1) ‘Validation of Analytical Procedures: Text and Methodology’. The method was linear over a concentration range of (1–7 µg/ml) with correlation coefficient of (r2 > 0.9999). The accuracy was confirmed by calculating the % recovery which was found to be 100.0–101.6%. The RSD values obtained for repeatability and intermediate precision experiments were less than 2%. The limit of detection (LOD) was 0.12 µg/ml, while the limit of quantification (LOQ) was 0.38 µg/ml. The drug samples were exposed to different stressed conditions and the results showed that all degradation products were satisfactorily separated from each other and from the peak of the drug using the developed method. The proposed method can be used for the quantitative determination of isotretinoin with confidence

Time invaders:conceptualizing performative game time

This chapter characterizes framing devices and other game elements as unstable signifiers, evaluating performances according to how they generate diachronic or synchronic effects by acting on those signifiers. Videogames make use of computers’ capabilities to present a very large set of these signifiers and thus generate highly complex forms of temporal experience. Because neither diachrony (exemplified by player performance) nor synchrony (computer-coded rule structures) can complete their respective operations and always leave a differential margin, videogames can be understood as diachrono-synchronic systems.Performative multiplicities of various sizes can be analyzed in terms of how they draw together or separate performances, creating a comparative methodology for describing temporal experience in videogames. One of the key synchronic effects is the Game Over, which has a high-level effect on all performances of a game. Considered as a synchronic horizon of experience, the Game Over provides a concept capable of addressing the heterogeneous and composite set of videogame elements in terms of how players interpret unstable signifiers. This includes narrative, which can be rigorously defined in terms of its synchronizing effect on a game’s performative multiplicity

Neutrino Scattering, Absorption and Annihilation above the accretion disks of Gamma Ray Bursts

The central engine that drives gamma ray burst (GRB) explosions may derive from the ability of electrons/positrons and nucleons to tap into the momentum and energy from the large neutrino luminosity emitted by an accretion disk surrounding a black hole. This transfer of momentum and energy occurs due to neutrino absorption, scattering, and annihilation and the non-spherical geometry of the source both increases the annihilation efficiency and, close to the black hole, directs the momentum transfer towards the disk axis. We present annihilation efficiencies and the momentum/energy transfers for a number of accretion disk models and compute the critical densities of infalling material below which the transfer of neutrino momentum/energy will lead to an explosion. Models in which the neutrinos and antineutrinos become trapped within the disk have noticeably different momentum and energy deposition structure compared to thin disk models that may lead to significant differences in the explosion dynamics