Edge momentum transport by neutrals: an interpretive numerical framework

Due to their high cross-field mobility, neutrals can contribute to momentum transport even at the low relative densities found inside the separatrix and they can generate intrinsic rotation. We use a charge-exchange dominated solution to the neutral kinetic equation, coupled to neoclassical ions, to evaluate the momentum transport due to neutrals. Numerical solutions to the drift-kinetic equation allow us to cover the full range of collisionality, including the intermediate levels typical of the tokamak edge. In the edge there are several processes likely to contribute to momentum transport in addition to neutrals. Therefore, we present here an interpretive framework that can evaluate the momentum transport through neutrals based on radial plasma profiles. We demonstrate its application by analysing the neutral angular momentum flux for an L-mode discharge in the ASDEX Upgrade tokamak. The magnitudes of the angular momentum fluxes we find here due to neutrals of 0.6 – 2 Nm are comparable to the net torque on the plasma from neutral beam injection, indicating the importance of neutrals for rotation in the edge.Vetenskapsrådet and Marie Sklodowska Curie Actions, Cofund, Project INCA 60039

Vortex ring refraction at large Froude numbers

We have experimentally studied the impact of an initially planar axisymmetric vortex ring, incident at an oblique angle, upon a gravity-induced interface separating two fluids of differing densities. After impact, the vortex ring was found to exhibit a variety of subsequent trajectories, which we organize according to both the incidence angle, $\theta_i$, and the interface strength, defined as the ratio of the Atwood and Froude numbers, $A/F$. For grazing incidence angles ($\theta_i \gtrsim 70$ deg.) vortices either penetrate or reflect from the interface, depending on whether the interface is weak or strong. In some cases, reflected vortices execute damped oscillations before finally disintegrating. For smaller incidence angles ($\theta_i \lesssim 70$ deg.) vortices penetrate the interface. When there is a strong interface, these vortices are observed to curve back up toward the interface. When there is a weak interface, these vortices are observed to refract downward, away from the interface. The critical interface strength below which vortex ring refraction is observed is given by $\log_{10}{(A/F)}= -2.38 \pm 0.05$.Comment: 26 pages, 11 figures; Submitted to Physical Review

IV.—Note on some Cretaceous Fossils from the Drift of Moreseat, Aberdeen

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Causality, delocalization and positivity of energy

In a series of interesting papers G. C. Hegerfeldt has shown that quantum systems with positive energy initially localized in a finite region, immediately develop infinite tails. In our paper Hegerfeldt's theorem is analysed using quantum and classical wave packets. We show that Hegerfeldt's conclusion remains valid in classical physics. No violation of Einstein's causality is ever involved. Using only positive frequencies, complex wave packets are constructed which at $t = 0$ are real and finitely localized and which, furthemore, are superpositions of two nonlocal wave packets. The nonlocality is initially cancelled by destructive interference. However this cancellation becomes incomplete at arbitrary times immediately afterwards. In agreement with relativity the two nonlocal wave packets move with the velocity of light, in opposite directions.Comment: 14 pages, 5 figure

The Interaction of New and Old Magnetic Fluxes at the Beginning of Solar Cycle 23

The 11-year cycle of solar activity follows Hale's law by reversing the magnetic polarity of leading and following sunspots in bipolar regions during the minima of activity. In the 1996-97 solar minimum, most solar activity emerged in narrow longitudinal zones - `active longitudes' but over a range in latitude. Investigating the distribution of solar magnetic flux, we have found that the Hale sunspot polarity reversal first occurred in these active zones. We have estimated the rotation rates of the magnetic flux in the active zones before and after the polarity reversal. Comparing these rotation rates with the internal rotation inferred by helioseismology, we suggest that both `old' and `new' magnetic fluxes were probably generated in a low-latitude zone near the base of the solar convection zone. The reversal of active region polarity observed in certain longitudes at the beginning of a new solar cycle suggests that the phenomenon of active longitudes may give fundamental information about the mechanism of the solar cycle. The non-random distribution of old-cycle and new-cycle fluxes presents a challenge for dynamo theories, most of which assume a uniform longitudinal distribution of solar magnetic fields.Comment: 4 pages, 5 figures; accepted for publication in ApJ Letter

The Response to a Perturbation in the Reflection Amplitude

We apply inverse scattering theory to calculate the functional derivative of the potential $V(x)$ and wave function $\psi(x,k)$ of a one-dimensional Schr\"odinger operator with respect to the reflection amplitude $r(k)$.Comment: 16 pages, no figure

Late Time Tail of Wave Propagation on Curved Spacetime

The late time behavior of waves propagating on a general curved spacetime is studied. The late time tail is not necessarily an inverse power of time. Our work extends, places in context, and provides understanding for the known results for the Schwarzschild spacetime. Analytic and numerical results are in excellent agreement.Comment: 11 pages, WUGRAV-94-1

Correction: Incorporating patient perspectives in the development of a core outcome set for reproductive genetic carrier screening: a sequential systematic review.

In Fig. 2 of this article, there is no references included; the figure should have appeared as shown below

Systematic review of outcomes in studies of reproductive genetic carrier screening: Towards development of a core outcome set.

PURPOSE: Current practice recommendations support the widespread implementation of reproductive genetic carrier screening (RGCS). These consensus-based recommendations highlight a research gap, with findings from current studies being insufficient to meet the standard required for more rigorous evidence-based recommendations. This systematic review assessed methodological aspects of studies on RGCS to inform the need for a core outcome set. METHODS: We conducted a systematic search to identify peer-reviewed published studies offering population-based RGCS. Study designs, outcomes, and measurement methods were extracted. A narrative synthesis was conducting using an existing outcome taxonomy and criteria used in the evaluation of genetic screening programs as frameworks. RESULTS: Sixty-five publications were included. We extracted 120 outcomes representing 24 outcome domains. Heterogeneity in outcome selection, measurement methods and time points of assessment was extensive. Quality appraisal raised concerns for bias. We found that reported outcomes had limited applicability to criteria used to evaluate genetic screening programs. CONCLUSION: Despite a large body of literature, diverse approaches to research have limited the conclusions that can be cumulatively drawn from this body of evidence. Consensus regarding meaningful outcomes for evaluation of RGCS would be a valuable first step in working towards evidence-based practice recommendations, supporting the development of a core outcome set

On the Localization of One-Photon States

Single photon states with arbitrarily fast asymptotic power-law fall-off of energy density and photodetection rate are explicitly constructed. This goes beyond the recently discovered tenth power-law of the Hellwarth-Nouchi photon which itself superseded the long-standing seventh power-law of the Amrein photon.Comment: 7 pages, tex, no figure