4,009 research outputs found
Holographic predictions for cosmological 3-point functions
We present the holographic predictions for cosmological 3-point correlators,
involving both scalar and tensor modes, for a universe which started in a
non-geometric holographic phase. Holographic formulae relate the cosmological
3-point functions to stress tensor correlation functions of a holographically
dual three-dimensional non-gravitational QFT. We compute these correlators at
1-loop order for a theory containing massless scalars, fermions and gauge
fields, and present an extensive analysis of the constraints due to Ward
identities showing that they uniquely determine the correlators up to a few
constants. We define shapes for all cosmological bispectra and compare the
holographic shapes to the slow-roll ones, finding that some are distinguishable
while others, perhaps surprisingly, are not.Comment: 51pp; 4 fig
The Structure of Martian Magnetosphere at the Dayside Terminator Region as Observed on MAVEN Spacecraft
We analyzed 44 passes of the MAVEN spacecraft through the magnetosphere,
arranged by the angle between electric field vector and the projection of
spacecraft position radius vector in the YZ plane in MSE coordinate system
( E ). All passes were divided into 3 angular sectors near 0{\deg},
90{\deg} and 180{\deg} E angles in order to estimate the role of IMF
direction in plasma and magnetic properties of dayside Martian magnetosphere.
The time interval chosen was from January 17 through February 4, 2016 when
MAVEN was crossing the dayside magnetosphere at SZA ~ 70{\deg}. Magnetosphere
as the region with prevailing energetic planetary ions is always found between
the magnetosheath and the ionosphere. 3 angular sectors of dayside interaction
region in MSE coordinate system with different orientation of the solar wind
electric field vector E = -1/c V x B showed that for each sector one can find
specific profiles of the magnetosheath, the magnetic barrier and the
magnetosphere. Plume ions originate in the northern MSE sector where motion
electric field is directed from the planet. This electric field ejects
magnetospheric ions leading to dilution of magnetospheric heavy ions
population, and this effect is seen in some magnetospheric profiles. Magnetic
barrier forms in front of the magnetosphere, and relative magnetic field
magnitudes in these two domains vary. The average height of the boundary with
ionosphere is ~530 km and the average height of the magnetopause is ~730 km. We
discuss the implications of the observed magnetosphere structure to the
planetary ions loss mechanism.Comment: 24 pages, 13 figure
Tautomeric mutation: A quantum spin modelling
A quantum spin model representing tautomeric mutation is proposed for any DNA
molecule. Based on this model, the quantum mechanical calculations for
mutational rate and complementarity restoring repair rate in the replication
processes are carried out. A possible application to a real biological system
is discussed.Comment: 7 pages (no figures
A scoping review of educational programmes on artificial intelligence (AI) available to medical imaging staff
Introduction Medical imaging is arguably the most technologically advanced field in healthcare, encompassing a range of technologies which continually evolve as computing power and human knowledge expand. Artificial Intelligence (AI) is the next frontier which medical imaging is pioneering. The rapid development and implementation of AI has the potential to revolutionise healthcare, however, to do so, staff must be competent and confident in its application, hence AI readiness is an important precursor to AI adoption. Research to ascertain the best way to deliver this AI-enabled healthcare training is in its infancy. The aim of this scoping review is to compare existing studies which investigate and evaluate the efficacy of AI educational interventions for medical imaging staff. Methods Following the creation of a search strategy and keyword searches, screening was conducted to determine study eligibility. This consisted of a title and abstract scan, then subsequently a full-text review. Articles were included if they were empirical studies wherein an educational intervention on AI for medical imaging staff was created, delivered, and evaluated. Results Of the initial 1309 records returned, n = 5 (∼0.4 %) of studies met the eligibility criteria of the review. The curricula and delivery in each of the five studies shared similar aims and a ‘flipped classroom’ delivery was the most utilised method. However, the depth of content covered in the curricula of each varied and measured outcomes differed greatly. Conclusion The findings of this review will provide insights into the evaluation of existing AI educational interventions, which will be valuable when planning AI education for healthcare staff. Implications for practice This review highlights the need for standardised and comprehensive AI training programs for imaging staff
Local diagnostic reference levels for skeletal surveys in suspected physical child abuse
NoIntroduction: The purpose was to determine if an age based, local diagnostic reference level for paediatric
skeletal surveys could be established using retrospective data.
Methods: All children below two years of age referred for a primary skeletal survey as a result of suspected physical abuse during 2017 or 2018 (n ¼ 45) were retrospectively included from a large Danish
university hospital. The skeletal survey protocol included a total of 33 images. Dose Area Product (DAP)
and acquisition parameters for all images were recorded from the Picture Archival and Communication
System (PACS) and effective dose was estimated. The 75th percentile for DAP was considered as the
diagnostic reference level (DRL).
Results: The 75th percentile for DAP was 314 mGy*cm2
, 520 mGy*cm2 and 779 mGy*cm2 for children <1
month, 1e11 months and 12 < 24 months of age respectively. However, only the age group 1e11 months
had a sufficient number of children (n ¼ 27) to establish a local DRL. Thus, for the other groups the DAP
result must be interpreted with caution. Effective dose was 0.19, 0.26 and 0.18 mSv for children <1, 1e11
months and 12 < 24 months of age respectively.
Conclusion: For children between 1 and 11 months of age, a local diagnostic reference level of
520 mGy*cm2 was determined. This may be used as an initial benchmark for primary skeletal surveys as
a result of suspected physical abuse for comparison and future discussion.
Implications for practice: While the data presented reflects the results of a single department, the suggested diagnostic reference level may be used as a benchmark for other departments when auditing
skeletal survey radiation dose
Phase field modeling of electrochemistry II: Kinetics
The kinetic behavior of a phase field model of electrochemistry is explored
for advancing (electrodeposition) and receding (electrodissolution) conditions
in one dimension. We described the equilibrium behavior of this model in [J. E.
Guyer, W. J. Boettinger, J.A. Warren, and G. B. McFadden, ``Phase field
modeling of electrochemistry I: Equilibrium'', cond-mat/0308173]. We examine
the relationship between the parameters of the phase field method and the more
typical parameters of electrochemistry. We demonstrate ohmic conduction in the
electrode and ionic conduction in the electrolyte. We find that, despite making
simple, linear dynamic postulates, we obtain the nonlinear relationship between
current and overpotential predicted by the classical ``Butler-Volmer'' equation
and observed in electrochemical experiments. The charge distribution in the
interfacial double layer changes with the passage of current and, at
sufficiently high currents, we find that the diffusion limited deposition of a
more noble cation leads to alloy deposition with less noble species.Comment: v3: To be published in Phys. Rev. E v2: Attempt to work around
turnpage bug. Replaced color Fig. 4a with grayscale 13 pages, 7 figures in 10
files, REVTeX 4, SIunits.sty, follows cond-mat/030817
Phase field modeling of electrochemistry I: Equilibrium
A diffuse interface (phase field) model for an electrochemical system is
developed. We describe the minimal set of components needed to model an
electrochemical interface and present a variational derivation of the governing
equations. With a simple set of assumptions: mass and volume constraints,
Poisson's equation, ideal solution thermodynamics in the bulk, and a simple
description of the competing energies in the interface, the model captures the
charge separation associated with the equilibrium double layer at the
electrochemical interface. The decay of the electrostatic potential in the
electrolyte agrees with the classical Gouy-Chapman and Debye-H\"uckel theories.
We calculate the surface energy, surface charge, and differential capacitance
as functions of potential and find qualitative agreement between the model and
existing theories and experiments. In particular, the differential capacitance
curves exhibit complex shapes with multiple extrema, as exhibited in many
electrochemical systems.Comment: v3: To be published in Phys. Rev. E v2: Added link to
cond-mat/0308179 in References 13 pages, 6 figures in 15 files, REVTeX 4,
SIUnits.sty. Precedes cond-mat/030817
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