Ultrahigh Energy Cosmic Ray Nuclei from Extragalactic Pulsars and the effect of their Galactic counterparts

The acceleration of ultrahigh energy nuclei in fast spinning newborn pulsars can explain the observed spectrum of ultrahigh energy cosmic rays and the trend towards heavier nuclei for energies above $10^{19}\,$eV as reported by the Auger Observatory. Pulsar acceleration implies a hard injection spectrum ($\sim E^{-1}$) due to pulsar spin down and a maximum energy $E_{\rm max} \sim Z \, 10^{19}$ eV due to the limit on the spin rate of neutron stars. We have previously shown that the escape through the young supernova remnant softens the spectrum, decreases slightly the maximum energy, and generates secondary nuclei. Here we show that the distribution of pulsar birth periods and the effect of propagation in the interstellar and intergalactic media modifies the combined spectrum of all pulsars. By assuming a normal distribution of pulsar birth periods centered at 300 ms, we show that the contribution of extragalactic pulsar births to the ultrahigh energy cosmic ray spectrum naturally gives rise to a contribution to very high energy cosmic rays (VHECRs, between $10^{16}$ and $10^{18}$ eV) by Galactic pulsar births. The required injected composition to fit the observed spectrum depends on the absolute energy scale, which is uncertain, differing between Auger Observatory and Telescope Array. The contribution of Galactic pulsar births can also bridge the gap between predictions for cosmic ray acceleration in supernova remnants and the observed spectrum just below the ankle, depending on the composition of the cosmic rays that escape the supernova remnant and the diffusion behavior of VHECRs in the Galaxy.Comment: 21 pages, 5 figure, JCAP submitte

Effect of intranasal oxytocin on pro-social behavior in social anxiety disorder

Previous research suggests that intranasal oxytocin may promote trust, social cooperation, in-group favoritism, and empathic concern in humans. Oxytocin therefore has therapeutic implications for psychological disorders such as social anxiety disorder (SAD). In particular, oxytocin may have anxiety-buffering effects in the context of social rejection. Oxytocin may promote cooperative social behavior with other individuals despite being rejected by them, as research has shown that oxytocin facilitates decisions indicative of sustained trust even despite breaches of trust. Using a double-blind, placebo-controlled design, the current investigation examined whether oxytocin modulates responses to social rejection from an initially cooperative confederate, and whether it modulates attentional processes toward social stimuli (disgust, neutral, and happy face stimuli). Participants were 54 individuals with SAD, who were randomly assigned to receive 24 international units (IU) of oxytocin or placebo nasal spray. Following drug administration, participants completed a computerized ball-tossing game called Cyberball, in which they were led to believe that they were playing "on-line" with three other fictitious players. The amount of reciprocation displayed by other players was manipulated, such that Player 1 was programmed to play cooperatively during the first half of the game (tossed 70% of his balls to the participant), and then switched to less cooperative play during the second half (tossed 10% of balls to the participant). After Cyberball, participants completed a modified version of the Posner Task. Results showed that oxytocin improved cooperation with Player 1 in the second half of the game, but only for individuals with low attachment avoidance. Oxytocin also amplified subjective ratings of perceived rejection by others during Cyberball for individuals with high rejection sensitivity. Furthermore, oxytocin led to facilitated disengagement from all social cues regardless of emotional valence and speeded up detection of disgust and neutral faces, compared to placebo, but only for individuals with high attachment avoidance. These findings suggest that oxytocin may promote social cooperation, as well as a flexible attentional pattern toward social cues, at least for some individuals with SAD. Future research should address individual differences in responses to oxytocin, and further investigate the comparative effects of oxytocin in healthy individuals

IceCube Constraints on Fast-Spinning Pulsars as High-Energy Neutrino Sources

Relativistic winds of fast-spinning pulsars have been proposed as a potential site for cosmic-ray acceleration from very high energies (VHE) to ultrahigh energies (UHE). We re-examine conditions for high-energy neutrino production, considering the interaction of accelerated particles with baryons of the expanding supernova ejecta and the radiation fields in the wind nebula. We make use of the current IceCube sensitivity in diffusive high-energy neutrino background, in order to constrain the parameter space of the most extreme neutron stars as sources of VHE and UHE cosmic rays. We demonstrate that the current non-observation of $10^{18}$ eV neutrinos put stringent constraints on the pulsar scenario. For a given model, birthrates, ejecta mass and acceleration efficiency of the magnetar sources can be constrained. When we assume a proton cosmic ray composition and spherical supernovae ejecta, we find that the IceCube limits almost exclude their significant contribution to the observed UHE cosmic-ray flux. Furthermore, we consider scenarios where a fraction of cosmic rays can escape from jet-like structures piercing the ejecta, without significant interactions. Such scenarios would enable the production of UHE cosmic rays and help remove the tension between their EeV neutrino production and the observational data.Comment: 23 pages, 8 figures; published in JCAP04(2016)01

Attachment style moderates the effects of oxytocin on social behaviors and cognitions during social rejection: applying an RDoC framework to social anxiety

Whereas the DSM categorizes individuals with similar self-reported symptoms, the Research Domain Criteria (RDoC) offers a new approach for classifying mental disorders based on dimensions of observable behaviors and neurobiological measures. The objective of this proof-of-concept study is to adopt this approach by distinguishing individuals based on disorder-related personality traits during an experimental manipulation that targeted a disorder-related biological mechanism. Specifically, we examined whether attachment style moderated the effect of oxytocin administration on social behaviors and cognitions during a social exclusion test in individuals with social anxiety disorder. When receiving oxytocin compared to placebo, only individuals with low attachment avoidance displayed more social affiliation and cooperation, and only those with high attachment avoidance showed faster detection of disgust and neutral faces. Thus, attachment style moderated oxytocin's effects among individuals who shared the same DSM diagnosis. We conclude that neurobiological tests can inform new classification strategies by adopting an RDoC framework.R01 AT007257 - NCCIH NIH HHS; R01 MH078308 - NIMH NIH HH

Feasibility of Neutron Coincidence Counting for Spent Fuel

High-temperature gas reactors rely on TRIstructural-ISOtropic (TRISO) fuel for enhanced fission product retention. Accurate fuel characterization would improve monitoring of efficient fuel usage and accountability. We developed a new neutron multiplicity counter (NMC) based on boron coated straw (BCS) detectors and used it in coincidence mode for 235U assay in TRISO fuel. In this work, we demonstrate that a high-efficiency version of the NMC encompassing 396 straws is able to estimate the 235U in used TRISO-fueled pebbles or compacts with a relative uncertainty below 2.5% in 100 s. We performed neutronics and fuel depletion calculation of the HTR-10 pebble bed reactor to estimate the neutron and gamma-ray source strengths of used TRISO-fueled pebbles with burnup between 9 and 90 GWd/t. Then, we measured a gamma-ray intrinsic efficiency of 10^-12 at an exposure rate of 340.87 R/h. The low gamma-ray sensitivity and high neutron detection efficiency enable the inspection of used fuel.Comment: 25 pages, 19 figure