Perception of drug teratogenicity among general practitioners and specialists in obstetrics/gynecology:a regional and national questionnaire-based survey

Cover letter to participants and online questionnaire. (DOC 27 kb

Ashkin-Teller universality in a quantum double model of Ising anyons

We study a quantum double model whose degrees of freedom are Ising anyons. The terms of the Hamiltonian of this system give rise to a competition between single and double topologies. By studying the energy spectra of the Hamiltonian at different values of the coupling constants, we find extended gapless regions which include a large number of critical points described by conformal field theories with central charge c=1. These theories are part of the Z_2 orbifold of the bosonic theory compactified on a circle. We observe that the Hilbert space of our anyonic model can be associated with extended Dynkin diagrams of affine Lie algebras which yields exact solutions at some critical points. In certain special regimes, our model corresponds to the Hamiltonian limit of the Ashkin-Teller model, and hence integrability over a wide range of coupling parameters is established.Comment: 11 pages, minor revision

Absence of a structural glass phase in a monoatomic model liquid predicted to undergo an ideal glass transition

We study numerically a monodisperse model of interacting classical particles predicted to exhibit a static liquid-glass transition. Using a dynamical Monte Carlo method we show that the model does not freeze into a glassy phase at low temperatures. Instead, depending on the choice of the hard-core radius for the particles the system either collapses trivially or a polycrystalline hexagonal structure emerges.Comment: 4 pages, 4 figures, minor changes in introduction and conclusions, additional reference

Falsely prolonged activated partial thromboplastin time – a pre- and post-analytical issue

This case highlights two common pre-analytical problems identified in routine coagulation testing of activated partial thromboplastin time (aPTT), which were overlooked because of a concurrent flag code indicating no coagulation and the result was replaced by asterisks. It concerns a boy with gastrointestinal bleeding and prolonged aPTT > 300 seconds, which raised the suspicion of haemophilia. When all other coagulation parameters (including specific coagulation factors VIII and IX) turned out to be normal, aPTT was re-measured using another analysis principle, which revealed a normal aPTT. The primary aPTT result turned out to be aborted due to concurrent haemolysis and lipaemia, but was erroneously interpreted as prolonged coagulation. The lesson is awareness of the possibility of numerous flag codes on the same sample overruling each other, and awareness on the responsibility in the post-analytical phase that must be carried by increased educational focus and by the manufacturers

Topology driven quantum phase transitions in time-reversal invariant anyonic quantum liquids

Indistinguishable particles in two dimensions can be characterized by anyonic quantum statistics more general than those of bosons or fermions. Such anyons emerge as quasiparticles in fractional quantum Hall states and certain frustrated quantum magnets. Quantum liquids of anyons exhibit degenerate ground states where the degeneracy depends on the topology of the underlying surface. Here we present a novel type of continuous quantum phase transition in such anyonic quantum liquids that is driven by quantum fluctuations of topology. The critical state connecting two anyonic liquids on surfaces with different topologies is reminiscent of the notion of a `quantum foam' with fluctuations on all length scales. This exotic quantum phase transition arises in a microscopic model of interacting anyons for which we present an exact solution in a linear geometry. We introduce an intuitive physical picture of this model that unifies string nets and loop gases, and provide a simple description of topological quantum phases and their phase transitions.Comment: 22 pages, 19 figure

Topological Phases: An Expedition off Lattice

Motivated by the goal to give the simplest possible microscopic foundation for a broad class of topological phases, we study quantum mechanical lattice models where the topology of the lattice is one of the dynamical variables. However, a fluctuating geometry can remove the separation between the system size and the range of local interactions, which is important for topological protection and ultimately the stability of a topological phase. In particular, it can open the door to a pathology, which has been studied in the context of quantum gravity and goes by the name of `baby universe', Here we discuss three distinct approaches to suppressing these pathological fluctuations. We complement this discussion by applying Cheeger's theory relating the geometry of manifolds to their vibrational modes to study the spectra of Hamiltonians. In particular, we present a detailed study of the statistical properties of loop gas and string net models on fluctuating lattices, both analytically and numerically.Comment: 38 pages, 22 figure

Anyonic quantum spin chains: Spin-1 generalizations and topological stability

There are many interesting parallels between systems of interacting non-Abelian anyons and quantum magnetism, occuring in ordinary SU(2) quantum magnets. Here we consider theories of so-called su(2)_k anyons, well-known deformations of SU(2), in which only the first k+1 angular momenta of SU(2) occur. In this manuscript, we discuss in particular anyonic generalizations of ordinary SU(2) spin chains with an emphasis on anyonic spin S=1 chains. We find that the overall phase diagrams for these anyonic spin-1 chains closely mirror the phase diagram of the ordinary bilinear-biquadratic spin-1 chain including anyonic generalizations of the Haldane phase, the AKLT construction, and supersymmetric quantum critical points. A novel feature of the anyonic spin-1 chains is an additional topological symmetry that protects the gapless phases. Distinctions further arise in the form of an even/odd effect in the deformation parameter k when considering su(2)_k anyonic theories with k>4, as well as for the special case of the su(2)_4 theory for which the spin-1 representation plays a special role. We also address anyonic generalizations of spin-1/2 chains with a focus on the topological protection provided for their gapless ground states. Finally, we put our results into context of earlier generalizations of SU(2) quantum spin chains, in particular so-called (fused) Temperley-Lieb chains.Comment: 37 pages, many figure

Collective States of Interacting Anyons, Edge States, and the Nucleation of Topological Liquids

Quantum mechanical systems, whose degrees of freedom are so-called su(2)_k anyons, form a bridge between ordinary SU(2) spin systems and systems of interacting non-Abelian anyons. Such a connection can be made for arbitrary spin-S systems, and we explicitly discuss spin-1/2 and spin-1 systems. Anyonic spin-1/2 chains exhibit a topological protection mechanism that stabilizes their gapless ground states and which vanishes only in the limit (k to infinity) of the ordinary spin-1/2 Heisenberg chain. For anyonic spin-1 chains we find their phase diagrams to closely mirror the one of the biquadratic SU(2) spin-1 chain. Our results describe at the same time nucleation of different 2D topological quantum fluids within a `parent' non-Abelian quantum Hall state, arising from a macroscopic occupation of localized, interacting anyons. The edge states between the `nucleated' and the `parent' liquids are neutral, and correspond precisely to the gapless modes of the anyonic chains.Comment: 4 pages, 2 figure

Psychological health of pregnant and postpartum women before and during the COVID-19 Pandemic

Background: The COVID-19 pandemic is likely to influence psychological health of pregnant and postpartum women.Methods: We conducted a non-concurrent cross-sectional study among 1145 women living in the Dutch-speaking part of Belgium, 541 pregnant and 604 postpartum women. We measured psychological health with the Whooley questions, Generalized Anxiety Disorder 2-item (GAD-2) and the Edinburgh Postnatal Depression Scale (EPDS) and compared the scores of pregnant and postpartum women before and during the COVID-19 pandemic.Results: No differences were observed in the Whooley, GAD-2 or EPDS scores among pregnant women. The postpartum total GAD-2 scores before vs during the pandemic showed significant differences. Controlling for confounders, we observed a small main positive effect of having an infant during time of COVID-19 (F(1.13) = 5.06, p.025, d.27). The effect was significantly larger for women with (a history of) perinatal psychological problems (F(1.12) = 51.44, p < .001, d.82). Emotional support was significantly related to GAD-2 scores of postpartum women during the pandemic (F(1.90) = 35.54, p < .001). Postpartum women reported significant higher effects of the pandemic on their behavior compared to pregnant women (p.034).Conclusion:The COVID-19 pandemic seems to have a positive effect on postpartum women during the first year postpartum, in particular for women with (a history of) perinatal psychological problems and for those women who experienced emotional support. The findings suggest that external stimuli caused by lockdown restrictions might have a positive effect on postpartum women’s emotional wellbeing. The sample consisted of white, educated women in arelationship and information regarding the extent of exposure to adverse COVID-19 consequences was lacking. We relied on self-selection and self-report. The postpartum pandemic sample was small