Nordic Institute for Theoretical Physics

Abstract Objectives Given the widespread use of period-tracking applications and evidence that some users rely on fertile-window predictions for pregnancy prevention, we aimed to quantify pregnancy risk arising from misclassification of biologically fertile days by period-tracking applications, and to compare this risk across calendar-based and basal body temperature (BBT)–supported period tracking and a digital contraceptive regulated as a medical device. Methods We conducted an observational analysis of cycles of mobile fertility application users who logged urinary luteinizing hormone (LH) tests. Biologically fertile days were defined using an LH-based reference fertile window (days −5 to 0 relative to ovulation). Three approaches were evaluated: a calendar-based period tracking application, a BBT-supported period tracking application, and a FDA-cleared digital contraceptive. Outcomes included day-specific frequency of fertile days misclassified as safe, cycle-level misclassification, and predicted pregnancy risk per cycle. Analyses were repeated in a subgroup of irregular cycles. Results 543,167 menstrual cycles with a clear LH surge signature were included in the analysis. Calendar-based period tracking frequently misclassified fertile days as safe, with 67% of cycles containing at least one at-risk day and 25% containing at least one high-risk day. The mean predicted pregnancy risk per cycle was 22%, increasing to 65% in irregular cycles. BBT-supported period tracking reduced misclassification but remained associated with substantial risk (41% of cycles with at least one at-risk day; mean predicted pregnancy risk 9%). In contrast, the digital contraceptive showed consistently low misclassification (3% of cycles with any at-risk day and a mean predicted pregnancy risk of 0.5%). Conclusions Both calendar-based and BBT-supported period-tracking applications not intended for contraception frequently misclassify biologically fertile days and should not be considered reliable tools for pregnancy prevention. Regulated digital contraceptives demonstrate substantially lower pregnancy risk. Short condensation Period-tracking apps frequently misclassify fertile days as safe, including days with high pregnancy risk. In a large real-world analysis, both calendar- and BBT-supported trackers showed substantial risk, unlike digital contraception methods regulated as a medical device.

Diabetic foot ulcers (DFUs) are a debilitating diabetes complication in which mitochondrial dysfunction and oxidative stress are prominent but mechanistically unresolved features. Here, we identify the mitochondria-encoded circular RNA (mecciRNA) circMT-RNR2 as a novel modulator of mitochondrial redox homeostasis in human skin wound healing. CircMT-RNR2 is reduced in DFU patient tissue and diabetic mouse wounds, enriched in dermal fibroblasts, and localized to mitochondria. Its loss impairs fibroblast proliferation, migration, extracellular matrix production, and contraction by destabilizing the mitochondrial antioxidant protein PRDX3, leading to elevated oxidative stress, mitochondrial damage, and mitophagy. In murine and human ex vivo wound models, circMT-RNR2 knockdown delays healing, whereas overexpression accelerates repair and boosts antioxidant defenses. These findings position circMT-RNR2 as a mitochondrial guardian of skin healing and a promising therapeutic target for DFU.

Abstract The local density of helicity (velocity–vorticity correlation) is expected to play an important role in turbulent transport of momentum. The helicity effect in inhomogeneous turbulence enters the Reynolds-stress expression as the coupling coefficient to the large-scale vorticity and rotation. These helicity turbulence models are extended to models of the subgrid-scale (SGS) stress, i.e. the helicity SGS models or H-SGS models. With the aid of high resolution direct numerical simulations (DNSs), the H-SGS models are validated to improve the standard Smagorinsky model. The helicity effect is applied to the effective angular-momentum transport in stellar convection. In the stellar convection zone, spatially inhomogeneous helicity distribution coupled with the steady meridional circulation contributes to the angular-momentum transport favourable to the prograde differential rotation.

Abstract The ongoing discussion about the atomic chemical composition of the Sun is commented on. The main focus in this review is on the deviation of the solar composition from that of most other solar-type stars in that its ratio of volatiles (like the elements C, N, O, S, P and Zn) to the refractories (most metals, like Ba, Ca, Ti, Y, Al, Sc and Zr) tends to be higher in the Sun by 10 to 20%. What does this tell about the formation and evolution of the Solar System? Scenarios in terms of galactic evolution, formation of the pre-solar nebula, of the evolution of the protoplanetary disk, of the engulfing of planets, and of other processes within the Solar System are considered, as well as the evolution of binary stars with similarly different chemical composition. Finally, implications, if any, on the habitability of the Solar System will be commented on.

ABSTRACT Dispersion measures (DM) of fast radio bursts (FRBs) probe the density of electrons in the intergalactic medium along their lines of sight, including the average density versus distance to the source and its variations in direction. While previous study focused on low redshift (e.g. $z\lesssim 5$), FRBs are potentially detectable out to high redshift, where their DMs can, in principle, probe the epoch of reionization (EoR) and its patchiness. We combine the cosmic density and ionization fields from large-scale radiation-hydro simulation Cosmic Dawn (CoDa) II of fully coupled galaxy formation and reionization to $z=5.8$ (where reionization ended at $z_{re}\approx 6.1$), with those from N-body simulation CoDa II–Dark Matter for the fully ionized post-EoR, from $z=5.8$ to the present. By calculating the mean and standard deviation of FRB DMs as functions of their source redshift, we are able to quantify the combined effect of self-consistent inhomogeneous density and ionization fields on FRB DMs for the first time. The mean and standard deviation of DM increase with redshift, and, assuming the CoDa reionization history, both reach a plateau by $z(x_{HII}\lesssim 0.25)\gtrsim 8$, i.e. well above $z_{re}$. The mean-DM asymptote $\mathcal {DM}_{\mathrm{ max}} \approx 5900~\mathrm{pc\, cm^{-3}}$ reflects the end of the EoR and its duration. The standard deviation there is $\sigma _{\mathrm{ DM}, \mathrm{ max}}\approx 497 ~\mathrm{pc\, cm^{-3}}$, reflecting inhomogeneities of both patchy reionization and density. Inhomogeneities in ionization during the EoR contribute $\mathcal {O}(1$ per cent) of this value of $\sigma _{\mathrm{ DM},\mathrm{ max}}$ from FRBs at redshifts $z\gtrsim 8$. Current estimates of FRB rates suggest this may be detectable within a few years of observation.

The XY-plaquette model is the most straightforward lattice realization of a broad class of fractonic field theories that host quasiparticles with restricted mobility. The plaquette interaction appears naturally as a ring-exchange term in the low-energy description of exciton Bose liquids, cold atomic gases, and quantum dimer models. Using first-principle Monte Carlo simulations, we study the phase diagram and the vortex dynamics in the XY-plaquette model on a square lattice in two spatial dimensions. In its minimal formulation, the model contains a ring-exchange plaquette term in two spatial dimensions and a standard XY-link term in the (imaginary) time direction. We show that the phase diagram of the minimal XY-plaquette model possesses two phases: (i) a disordered vortex-dominated phase in which a single percolating vortex trajectory occupies the whole three-dimensional spacetime; (ii) a partially disordered phase in which the vortices become partially immobile, with their worldlines strictly confined to one or several infinite two-dimensional planes. The spatial positions and spatial orientations (along x or y axis) of these vortex domain walls appear to be spontaneous. Individual vortices form a disordered system within each vortex domain wall, so the fractal spacetime dimension of vortex trajectories approaches Df=2. We argue that the appearance of the vortex walls could be interpreted as a consequence of the spontaneous breaking of a global internal symmetry in the compact XY-plaquette model. Published by the American Physical Society 2025

Abstract Turbulent flows are known to produce enhanced effective magnetic and passive scalar diffusivities, which can fairly accurately be determined with numerical methods. It is now known that, if the flow is also helical, the effective magnetic diffusivity is reduced relative to the nonhelical value. Neither the usual second-order correlation approximation nor the various τ approaches have been able to capture this. Here we show that the helicity effect on the turbulent passive scalar diffusivity works in the opposite sense and leads to an enhancement. We have also demonstrated that the correlation time of the turbulent velocity field increases with the kinetic helicity. This is a key point in the theoretical interpretation of the obtained numerical results. Simulations in which helicity is being produced self-consistently by stratified rotating turbulence resulted in a turbulent passive scalar diffusivity that was found to be decreasing with increasing rotation rate.

High-dimensional systems are an important frontier for photonic quantum correlation experiments. These correlation tests commonly prescribe measurements with many possible outcomes but they are often implemented through many individual binary-outcome measurements that use only a single-detector. Here, we discuss how this binarization procedure for multioutcome measurements can open a loophole, unless specific device-characterization assumptions are satisfied. We highlight that correlation tests designed for multioutcome measurements can be trivialized in binarized implementations and we then show how to accurately analyze binarized data to reveal their quantum features. For seminal types of correlation experiments, such as Bell inequality tests, steering tests and prepare-and-measure experiments, we find that binarization may incur a sizable cost in the magnitude of quantum advantages. This emphasizes the importance of both accurate data analysis and implementing genuinely multioutcome measurements in high-dimensional correlation experiments.