Stochastic theory of lineshape broadening in quasielastic He atom scattering with interacting adsorbates

The activated surface diffusion of interacting adsorbates is described in terms of the so-called interacting single adsorbate approximation, which is applied to the diffusion of Na atoms on Cu(001) for coverages up to 20% in quasielastic He atom scattering experiments. This approximation essentially consists of solving the standard Langevin equation with two noise sources and frictions: a Gaussian white noise accounting for the friction with the substrate, and a white shot noise characterized by a collisional friction simulating the adsorbate-adsorbate collisions. The broadenings undergone by the quasielastic peak are found to be in very good agreement with the experimental data reported at two surface temperatures 200 and 300 K.Comment: 6 pages, 3 figure

Understanding chemical reactions within a generalized Hamilton-Jacobi framework

Reaction paths and classical and quantum trajectories are studied within a generalized Hamilton-Jacobi framework, which allows to put on equal footing topology and dynamics in chemical reactivity problems. In doing so, we show how high-dimensional problems could be dealt with by means of Caratheodory plots or how trajectory-based quantum-classical analyses reveal unexpected discrepancies. As a working model, we consider the reaction dynamics associated with a Mueller-Brown potential energy surface, where we focus on the relationship between reaction paths and trajectories as well as on reaction probability calculations from classical and quantum trajectories.Comment: 22 pages, 5 figures, 1 tabl

Linear response theory of activated surface diffusion with interacting adsorbates

Activated surface diffusion with interacting adsorbates is analyzed within the Linear Response Theory framework. The so-called interacting single adsorbate model is justified by means of a two-bath model, where one harmonic bath takes into account the interaction with the surface phonons, while the other one describes the surface coverage, this leading to defining a collisional friction. Here, the corresponding theory is applied to simple systems, such as diffusion on flat surfaces and the frustrated translational motion in a harmonic potential. Classical and quantum closed formulas are obtained. Furthermore, a more realistic problem, such as atomic Na diffusion on the corrugated Cu(001) surface, is presented and discussed within the classical context as well as within the framework of Kramer's theory. Quantum corrections to the classical results are also analyzed and discussed.Comment: 40 pages, 4 figure

Validation of the UNC OCT Index for the Diagnosis of Early Glaucoma

Purpose:To independently validate the performance of the University of North Carolina Optical Coherence Tomography (UNC OCT) Index in diagnosing and predicting early glaucoma. Methods:Data of 118 normal subjects (118 eyes) and 96 subjects (96 eyes) with early glaucoma defined as visual field mean deviation (MD) greater than -4 decibels (dB), aged 40 to 80 years, and who were enrolled in the Full-Threshold Testing Size III, V, VI comparison study were used in this study. CIRRUS OCT average and quadrants' retinal nerve fiber layer (RNFL); optic disc vertical cup-to-disc ratio (VCDR), cup-to-disc area ratio, and rim area; and average, minimum, and six sectoral ganglion cell-inner plexiform layer (GCIPL) measurements were run through the UNC OCT Index algorithm. Area under the receiver operating characteristic curve (AUC) and sensitivities at 95% and 99% specificity were calculated and compared between single parameters and the UNC OCT Index. Results:Mean age was 60.1 ± 11.0 years for normal subjects and 66.5 ± 8.1 years for glaucoma patients (P < 0.001). MD was 0.29 ± 1.04 dB and -1.30 ± 1.35 dB in normal and glaucomatous eyes (P < 0.001), respectively. The AUC of the UNC OCT Index was 0.96. The best single metrics when compared to the UNC OCT Index were VCDR (0.93, P = 0.054), average RNFL (0.92, P = 0.014), and minimum GCIPL (0.91, P = 0.009). The sensitivities at 95% and 99% specificity were 85.4% and 76.0% (UNC OCT Index), 71.9% and 62.5% (VCDR, all P < 0.001), 64.6% and 53.1% (average RNFL, all P < 0.001), and 66.7% and 58.3% (minimum GCIPL, all P < 0.001), respectively. Conclusions:The findings confirm that the UNC OCT Index may provide improved diagnostic perforce over that of single OCT parameters and may be a good tool for detection of early glaucoma. Translational Relevance:The UNC OCT Index algorithm may be incorporated easily into routine clinical practice and be useful for detecting early glaucoma

Validation of the UNC OCT Index for the Diagnosis of Early Glaucoma

Observations of binary stars containing an accreting black hole or neutron star often show x-ray emission extending to high energies (>10 kilo­–electron volts), which is ascribed to an accretion disk corona of energetic particles akin to those seen in the solar corona. Despite their ubiquity, the physical conditions in accretion disk coronae remain poorly constrained. Using simultaneous infrared, optical, x-ray, and radio observations of the Galactic black hole system V404 Cygni, showing a rapid synchrotron cooling event in its 2015 outburst, we present a precise 461 ± 12 gauss magnetic field measurement in the corona. This measurement is substantially lower than previous estimates for such systems, providing constraints on physical models of accretion physics in black hole and neutron star binary systems

New insights into measurement variability in glaucomatous visual fields from computer modelling.

To develop a model to simulate visual fields (VFs) in glaucoma patients, and to characterize variability of the Mean Deviation (MD) VF summary measurement using real VFs and simulations

Visual Loss and Visual Hallucinations in Patients with Age-Related Macular Degeneration (Charles Bonnet Syndrome)

PURPOSE. The condition in which visual hallucinations (VHs) are solely associated with a visual impairment is termed Charles Bonnet Syndrome (CBS). The study was undertaken to investigate whether the extent of visual acuity (VA) loss and central visual field loss predisposes a patient with age-related macular degeneration (AMD) to develop a CBS VH and, in addition, whether the progression in loss is mirrored in the complexity of the VHs reported. VH phenomenology and CBS prevalence were also examined. METHODS. Sixty-six patients (age range, 63-96 years, mean Ϯ SD 81.2 Ϯ 7.1 years) with bilateral AMD were questioned as to whether they had experienced any hallucinatory episodes exclusive to vision. The four-point primary inclusion criterion ensured that all patients had bilateral AMD, a bilateral central scotoma, best monocular VA poorer than or equal to 0.6 logMAR (logarithm of the minimum angle of resolution) and intact cognition (using the Mini Mental State Examination for the Blind and the Telephone Interview for Cognitive Status). The patients who did not report VH were classified into the non-VH group, with the remainder in the VH group. An extended Institute of Psychiatry Structural Interview characterized the phenomenology of the VH. A secondary inclusion criterion subdivided the VH group into the apparent CBS group, in which personal medical history may have contributed to VH generation, and the manifest CBS group, where VHs were solely as a result of the visual loss. RESULTS. Fifty-three patients met the primary inclusion criterion: 32 were classified into the non-VH group and 21 into the VH group. The VH group were slightly younger (median difference, 4 years, P ϭ 0.03) and appeared to have a lower VA (median difference, 0.20 logMAR, P ϭ 0.08) and a more extensive visual field loss (P ϭ 0.06) than did the non-VH group. However, when these variables were evaluated simultaneously by logistic regression, only age emerged as a statistically significant predictor of VH (odds ratio 0.88, 95% confidence interval [CI] 0.8 -0.99, P ϭ 0.03). The prevalence of apparent CBS and manifest CBS in the AMD population was found to be 25% and 15%, respectively. With no clinical and phenomenological differences between the two CBS groups, the secondary inclusion criterion was withdrawn, the VH group was renamed the CBS group, and a prevalence of 40% was recalculated. Of the 82 visual phenomena experienced by the CBS group, 21 were classified as simple VHs and 39 as complex VHs, with the remainder classified as either entopic phenomena or visual inference. Patients who experienced both simple and complex VHs appeared to have a greater visual field loss (P ϭ 0.06) compared with those patients who reported either solely simple or solely complex VHs. CONCLUSIONS. The extent of visual loss did not appear to be a predictor for the likelihood of a patient with AMD experiencing a CBS VH, nor was the progression of loss reflected in the complexity of the VHs reported. 1,2 can occur in any sensory modality, and are most often generated through neurologic disease, psychopathology, and the use of drugs. 2-6 When visual hallucinations (VHs) follow marked visual acuity (VA) loss, in the absence of cognitive impairment, the condition is termed Charles Bonnet Syndrome (CBS), To ensure that there was little likelihood that factors such as cognitive impairment would contribute to the perception of the VH we applied a four-point primary inclusion criterion to the group of patients with AMD. A secondary two-point criterion subdivided the VH group into two groups: an apparent CBS group, in which concurrent medication and/or a diagnosed medical condition could have contributed to the generation of the VHs, and a manifest CBS group, in which there were no obvious causes for the VHs other than the marked visual impairment. Our findings suggest that the VH experienced by the apparent CBS group could not be differentiated from those described by the manifest CBS group. Furthermore, the extent of visual loss did not predict which patients would visually hallucinate, nor did it determine the complexity of the VHs reported. MATERIALS AND METHODS Study Inclusion Criteria An initial group of 66 consecutive fluent-English-speaking patients with AMD were recruited from the Manchester Roya