Excitations in time-dependent density-functional theory

An approximate solution to the time-dependent density functional theory (TDDFT) response equations for finite systems is developed, yielding corrections to the single-pole approximation. These explain why allowed Kohn-Sham transition frequencies and oscillator strengths are usually good approximations to the true values, and why sometimes they are not. The approximation yields simple expressions for G\"orling-Levy perturbation theory results, and a method for estimating expectation values of the unknown exchange-correlation kernel.Comment: 4 pages, 1 tabl

Continuum states from time-dependent density functional theory

Linear response time-dependent density functional theory is used to study low-lying electronic continuum states of targets that can bind an extra electron. Exact formulas to extract scattering amplitudes from the susceptibility are derived in one dimension. A single-pole approximation for scattering phase shifts in three dimensions is shown to be more accurate than static exchange for singlet electron-He$^+$ scattering.Comment: 5 pages, 2 figures, J. Chem. Phys. accepte

Ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV above threshold

We present here triple differential cross sections for ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV energy above threshold, calculated in the hyperspherical partial wave theory. The results are in very good agreement with the available semiclassical results of Deb and Crothers \cite{DC02} for these energies. With this, we are able to demonstrate that the hyperspherical partial wave theory yields good cross sections from 30 eV \cite{DPC03} down to near threshold for equal energy sharing kinematics.Comment: 6 pages, 9 figure

Chest X-Ray interpretation: agreement between consultant radiologists and a reporting radiographer in clinical practice in the United Kingdom

Rationale: Driven by developing technology and an ageing population, radiology has witnessed an unprecedented rise in workload. One response to this in the United Kingdom has been to train radiographers to undertake clinical reporting. Accurate interpretation of imaging is crucial to allow clinicians' to correctly manage and treat patients. Methods: A random sample of cases (n=100) was selected from a consecutive series of 1,000 chest x-ray reports produced by a radiographer in clinical practice using a simple computer generated algorithm. Due to the high level of observer variation which is apparent when interpreting chest x-rays, three consultant radiologists were also included to establish the rate of inter-observer variation between radiologists, which was then used as the baseline. Fifty images were interpreted by each radiologist who examined the radiographer report for accuracy and agreement, with 50% duplication of cases between radiologists to determine inter-radiologist variation. The radiologists performed their evaluation independently and blinded to the proportion of cases receiving multiple radiologist opinions. Inter-observer agreement analysis using Kappa was performed to determine consistency among observers. Results: Disagreement was found between the radiologist and radiographer in 7 cases, which in three instances showed agreement between one radiologist and the radiographer. Inter-observer agreement (Kappa statistic) between the three radiologists and the reporting radiographer was found to be almost perfect, K=0.91, 95% confidence interval (0.79,1.0), K=0.91 (0.78,1.0) and K=0.83 (0.68,0.99) respectively. Inter-radiologist agreement was also almost perfect, K=0.82 (0.57,1.0) and K=0.91 (0.75,1.0). Conclusion: The level of inter-observer agreement between radiologist and reporting radiographer chest x-ray interpretation compares favourably with inter-radiologist variation

R-matrix Floquet theory for laser-assisted electron-atom scattering

A new version of the R-matrix Floquet theory for laser-assisted electron-atom scattering is presented. The theory is non-perturbative and applicable to a non-relativistic many-electron atom or ion in a homogeneous linearly polarized field. It is based on the use of channel functions built from field-dressed target states, which greatly simplifies the general formalism.Comment: 18 pages, LaTeX2e, submitted to J.Phys.

On the density-potential mapping in time-dependent density functional theory

The key questions of uniqueness and existence in time-dependent density functional theory are usually formulated only for potentials and densities that are analytic in time. Simple examples, standard in quantum mechanics, lead however to non-analyticities. We reformulate these questions in terms of a non-linear Schr\"odinger equation with a potential that depends non-locally on the wavefunction.Comment: 8 pages, 2 figure

Addressing environmental and atmospheric challenges for capturing high-precision thermal infrared data in the field of astro-ecology

Using thermal infrared detectors mounted on drones, and applying techniques from astrophysics, we hope to support the field of conservation ecology by creating an automated pipeline for the detection and identification of certain endangered species and poachers from thermal infrared data. We test part of our system by attempting to detect simulated poachers in the field. Whilst we find that we can detect humans hiding in the field in some types of terrain, we also find several environmental factors that prevent accurate detection, such as ambient heat from the ground, absorption of infrared emission by the atmosphere, obscuring vegetation and spurious sources from the terrain. We discuss the effect of these issues, and potential solutions which will be required for our future vision for a fully automated drone-based global conservation monitoring system.Comment: Published in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2018. 8 pages, 3 figure

Agreement between expert thoracic radiologists and the chest radiograph reports provided by consultant radiologists and reporting radiographers in clinical practice: review of a single clinical site

Introduction: To compare the clinical chest radiograph (CXR) reports provided by consultant radiologists and reporting radiographers with expert thoracic radiologists. Methods: Adult CXRs (n=193) from a single site were included; 83% randomly selected from CXRs performed over one year, and 17% selected from the discrepancy meeting. Chest radiographs were independently interpreted by two expert thoracic radiologists (CTR1/2).Clinical history, previous and follow-up imaging was available, but not the original clinical report. Two arbiters compared expert and clinical reports independently. Kappa (Ƙ), Chi Square (χ2) and McNemar tests were performed to determine inter-observer agreement. Results: CTR1 interpreted 187 (97%) and CTR2 186 (96%) CXRs, with 180 CXRs interpreted by both experts. Radiologists and radiographers provided 93 and 87 of the original clinical reports respectively. Consensus between both expert thoracic radiologists and the radiographer clinical report was 70 (CTR1;Ƙ=0.59) and 70 (CTR2; Ƙ=0.62), and comparable to agreement between expert thoracic radiologists and the radiologist clinical report (CTR1=76,Ƙ=0.60; CTR2=75, Ƙ=0.62). Expert thoracic radiologists agreed in 131 cases (Ƙ=0.48). There was no difference in agreement between either expert thoracic radiologist, when the clinical report was provided by radiographers or radiologists (CTR1 χ=0.056, p=0.813; CTR2 χ=0.014, p=0.906), or when stratified by inter-expert agreement; radiographer McNemar p=0.629 and radiologist p=0.701. Conclusion: Even when weighted with chest radiographs reviewed at discrepancy meetings, content of CXR reports from trained radiographers are comparable to the content of reports issued by radiologists and expert thoracic radiologists