A Large Effective Phonon Magnetic Moment in a Dirac Semimetal

We investigated the magnetoterahertz response of the Dirac semimetal Cd$_3$As$_2$ and observed a particularly low frequency optical phonon, as well as a very prominent and field sensitive cyclotron resonance. As the cyclotron frequency is tuned with field to pass through the phonon, the phonon become circularly polarized as shown by a notable splitting in their response to right- and left-hand polarized light. This splitting can be expressed as an effective phonon magnetic moment that is approximately 2.7 times the Bohr magneton, which is almost four orders of magnitude larger than ab initio calculations predict for phonon magnetic moments in nonmagnetic insulators. This exceedingly large value is due to the coupling of the phonons to the cyclotron motion and is controlled directly by the electron-phonon coupling constant. This field tunable circular-polarization selective coupling provides new functionality for nonlinear optics to create light-induced topological phases in Dirac semimetals.Comment: 15 pages for main text and SI; To appear in Nano Letters (2020

Chaotic Quantum Decay in Driven Biased Optical Lattices

Quantum decay in an ac driven biased periodic potential modeling cold atoms in optical lattices is studied for a symmetry broken driving. For the case of fully chaotic classical dynamics the classical exponential decay is quantum mechanically suppressed for a driving frequency \omega in resonance with the Bloch frequency \omega_B, q\omega=r\omega_B with integers q and r. Asymptotically an algebraic decay ~t^{-\gamma} is observed. For r=1 the exponent \gamma agrees with $q$ as predicted by non-Hermitian random matrix theory for q decay channels. The time dependence of the survival probability can be well described by random matrix theory. The frequency dependence of the survival probability shows pronounced resonance peaks with sub-Fourier character.Comment: 7 pages, 5 figure

Does cognitive inflexibility predict violent extremist behaviour intentions? A registered direct replication report of Zmigrod et al., 2019

Purpose: Zmigrod et al. (2019a, Frontiers in Psychology, 10, 989) demonstrated that lower levels of cognitive flexibility predict a higher willingness to fight and die for the national in-group. We conducted a registered direct replication of their Study 1. Extending the original study, we examined whether the documented relationship held when a self-report measure for cognitive flexibility was introduced and when identity fusion was controlled for. We also investigated whether cognitive inflexibility predicts normative pro-group behaviour intentions. // Methods: Participants (N = 1378) reported in a cross-sectional survey study their willingness to fight, die and sacrifice themselves for the in-group and completed the Remote Associates (RAT) as and Wisconsin Card Sorting (WCST) tests. Afterwards, self-reported cognitive flexibility, identity fusion and normative pro-group behaviour intentions were assessed. // Results: Results showed a small negative relationship between RAT accuracy rates and willingness to fight and die. WCST accuracy rates were positively related with willingness to die but not correlated with willingness to fight. Self-report measures of cognitive flexibility were partially positively and partially negatively associated with support for violent extremism. There was further evidence that lower cognitive flexibility predicts higher normative pro-group behaviour intentions. A mini meta-analysis, which synthesized findings from the original study and our replication, demonstrated a relatively small negative correlation between cognitive flexibility and support for violent extremism. // Conclusions: In summary, even though not all individual results could be replicated, we confirmed the overall conclusion of the original study: lower cognitive flexibility predicted stronger willingness to fight and die for an in-group. The findings highlight that it is important to integrate cognitive style in multi-level frameworks of risk factors of violent extremism. Additionally, our results point out that the validity of different measures of cognitive flexibility, including self-report tools, must be further examined. Future research that evaluates cognitive flexibility training in the context of CVE/PVE interventions is also encouraged

The Base Rate Study: Developing Base Rates for Risk Factors and Indicators for Engagement in Violent Extremism

Improvements have been made in identifying the prevalence of risk factors/indicators for violent extremism. A consistent problem is the lack of base rates. How to develop base rates is of equal concern. This study has two aims: (i) compare two methods for developing base rates; the Unmatched Count Technique (UCT) and direct questioning, (ii) generate base rates in a general population sample and compare these to a sample of lone‐actor terrorists (n = 125). We surveyed 2108 subjects from the general population. Participants were recruited from an online access panel and randomly assigned to one of three conditions; direct survey, control, or UCT. Survey items were based on a lone‐actor terrorist codebook developed from the wider literature. Direct questioning was more suitable under our study conditions where UCT resulted in deflation effects. Comparing the base rates identified a number of significant differences: (i) lone‐actor terrorists demonstrated propensity indicators related to a cognitive susceptibility, and a crime‐ and/or violence‐supportive morality more often; the general sample demonstrated protective factors more often, (ii) lone‐actor terrorists demonstrated situational indicators related to a crime‐ and/or violence‐supportive morality more often, whereas the general sample experienced situational stressors more often, (iii) lone‐actor terrorists demonstrated indicators related to exposure to extremism more often. Results suggest there are measurable differences in the prevalence of risk factors between lone‐actor terrorists and the general population. However, no single factor “predicts” violent extremism. This bears implications for our understanding of the interrelation of risk and protective factors, and for the risk assessment of violent extremism

Denaturation transition of stretched DNA

We generalize the Poland-Scheraga model to consider DNA denaturation in the presence of an external stretching force. We demonstrate the existence of a force-induced DNA denaturation transition and obtain the temperature-force phase diagram. The transition is determined by the loop exponent $c$ for which we find the new value $c=4\nu-1/2$ such that the transition is second order with $c=1.85<2$ in $d=3$. We show that a finite stretching force $F$ destabilizes DNA, corresponding to a lower melting temperature $T(F)$, in agreement with single-molecule DNA stretching experiments.Comment: 5 pages, 3 figure

An in vivo evaluation of Brilliant Blue G in animals and humans

Background/Aims: To evaluate the retinal toxicity of Brilliant Blue G (BBG) following intravitreal injection in rat eyes and examine the biocompatibility and the staining properties in humans.Methods: BBG was injected into the 11 rat eyes to evaluate toxic effects with balanced salt solution (BSS) serving as control. Retinal toxicity was assessed by retinal ganglion cell (RGC) counts and by light microscopy 7 days later. In addition, BBG was applied during vitrectomy for macular hole (MH) (n = 15) or epiretinal membranes (ERM) (n = 3) in a prospective, non-comparative consecutive series of patients. Before and after surgery, all patients underwent a complete clinical examination including measurement of best corrected visual acuity (VA) and intraocular pressure, perimetry, fundus photography and optical coherence tomography. Patients were seen 1 day before surgery and then in approximately four weeks intervals.Results: No significant reduction in RGC numbers and no morphological alterations were noted. A sufficient staining of the internal limiting membrane (ILM) was seen in patients with MH, while the staining pattern in ERM cases was patchy, indicating that parts of the ILM were peeled off along with the ERM in a variable extent. All MHs could be closed successfully. VA improved in 10 eyes (56%; 8/15 MH patients, 2/3 ERM patients), was unchanged in four eyes (22%; all MH patients) and was reduced in four eyes (22%; 3/15 MH, 1/3 ERM). No toxic effects attributable to the dye were noted during patient follow-up. The ultrastructure of tissue harvested during surgery was unremarkable.Conclusion: Brilliant Blue provides a sufficient and selective staining of the ILM. No retinal toxicity or adverse effects related to the dye were observed in animal and human studies. The long-term safety of this novel dye will have to be evaluated in larger patient series and a longer follow-up