Geometrical optics for scalar, electromagnetic and gravitational waves in curved spacetime

The geometrical-optics expansion reduces the problem of solving wave equations to one of solving transport equations along rays. Here we consider scalar, electromagnetic and gravitational waves propagating on a curved spacetime in general relativity. We show that each is governed by a wave equation with the same principal part. It follows that: each wave propagates at the speed of light along rays (null generators of hypersurfaces of constant phase); the square of the wave amplitude varies in inverse proportion to the cross section of the beam; and the polarization is parallel-propagated along the ray (the Skrotskii/Rytov effect). We show that the optical scalars for a beam, and various Newman-Penrose scalars describing a parallel-propagated null tetrad, can be found by solving transport equations in a second-order formulation. Unlike the Sachs equations, this formulation makes it straightforward to find such scalars beyond the first conjugate point of a congruence, where neighbouring rays cross, and the scalars diverge. We discuss differential precession across the beam which leads to a modified phase in the geometrical-optics expansion.Comment: 17 pages, 1 figure. Proceedings for IV Amazonian Symposium on Physics, Belem, Brazil at UFPA on 18-22 Sep 201

A quality improvement project using a problem based post take ward round proforma based on the SOAP acronym to improve documentation in acute surgical receiving

Objectives: Ward round documentation provides one of the most important means of communication between healthcare professionals. We aimed to establish if the use of a problem based standardised proforma can improve documentation in acute surgical receiving. Methods: Gold standards were established using the RCSE record keeping guidelines. We audited documentation for seven days using the following headings: patient name/identification number, subjective findings, objective findings, clinical impression/diagnosis, plan, diet status, discharge decision, discharge planning, signature, and grade. After the initial audit cycle, a ward round proforma was introduced using the above headings and re-audited over a seven day period. Results: The pre-intervention arm contained 50 patients and the post intervention arm contained 47. The following headings showed an improvement in documentation compliance to 100%: patient name/identification number vs 96%, subjective findings vs 84%, objective findings vs 48%, plan vs 98%, signature vs 96%, and grade vs 62%. Documentation of the clinical impression/diagnosis improved to 98% vs 30%, diet status rose to 83% vs 16%, discharge decision to 66% vs 16%, and discharge planning to 40% vs 20%. Conclusions: Standardised proformas improve the documentation of post-take ward round notes. This helps to clarify the onward management plan for all aspects of a patient's care and will help avoid adverse events and litigation. This should improve the quality and safety of Patient Care

The Information Geometry of the One-Dimensional Potts Model

In various statistical-mechanical models the introduction of a metric onto the space of parameters (e.g. the temperature variable, $\beta$, and the external field variable, $h$, in the case of spin models) gives an alternative perspective on the phase structure. For the one-dimensional Ising model the scalar curvature, ${\cal R}$, of this metric can be calculated explicitly in the thermodynamic limit and is found to be ${\cal R} = 1 + \cosh (h) / \sqrt{\sinh^2 (h) + \exp (- 4 \beta)}$. This is positive definite and, for physical fields and temperatures, diverges only at the zero-temperature, zero-field ``critical point'' of the model. In this note we calculate ${\cal R}$ for the one-dimensional $q$-state Potts model, finding an expression of the form ${\cal R} = A(q,\beta,h) + B (q,\beta,h)/\sqrt{\eta(q,\beta,h)}$, where $\eta(q,\beta,h)$ is the Potts analogue of $\sinh^2 (h) + \exp (- 4 \beta)$. This is no longer positive definite, but once again it diverges only at the critical point in the space of real parameters. We remark, however, that a naive analytic continuation to complex field reveals a further divergence in the Ising and Potts curvatures at the Lee-Yang edge.Comment: 9 pages + 4 eps figure

Evaluation of land use mapping from ERTS in the shore zone of CARETS

Imagery of the Atlantic shoreline zone of the Central Atlantic Regional Ecological Test Site (CARETS) was evaluated for classifying land use and land cover, employing the USGS Geographic Application Program's land use classification system. ERTS data can provide a basis for land cover and land use mapping within the shoreline zone, however because of the dynamic nature of this environment, two additional terms are considered: vulnerability of classes to storms and progressive erosion, and sensitivity of the classes to man's activities

LANDSAT Application of Remote Sensing to Shoreline Form Analysis

There are no author-identified significant results in this report

Action and valence modulate choice and choice-induced preference change.

Choices are not only communicated via explicit actions but also passively through inaction. In this study we investigated how active or passive choice impacts upon the choice process itself as well as a preference change induced by choice. Subjects were tasked to select a preference for unfamiliar photographs by action or inaction, before and after they gave valuation ratings for all photographs. We replicate a finding that valuation increases for chosen items and decreases for unchosen items compared to a control condition in which the choice was made post re-evaluation. Whether choice was expressed actively or passively affected the dynamics of revaluation differently for positive and negatively valenced items. Additionally, the choice itself was biased towards action such that subjects tended to choose a photograph obtained by action more often than a photographed obtained through inaction. These results highlight intrinsic biases consistent with a tight coupling of action and reward and add to an emerging understanding of how the mode of action itself, and not just an associated outcome, modulates the decision making process

Population dynamics of \u3cem\u3eLudwigia leptocarpa\u3c/em\u3e (Onagraceae) and some factors affecting size hierarchies in a natural population

Germination cohorts of Ludwigia leptocarpa, a semi-aquatic annual plant were marked in the field at time of establishment and followed through the 1981 and 1982 growing seasons at a site in southern South Carolina. Data from each cohort were pooled to determine demographic characteristics of the population as a whole, then analyzed separately to determine the effect of time on germination on survivorship, relative growth rate, and adult size. Changes in numbers of L. leptocarpa fit a Deevey Type II survivorship curve. This and other characteristics of the species classify it as ‘r-selected’. Aspects of the life history may reflect a ‘bet-hedging’ stratagem that ensures establishment. Differences in the time of germination are not responsible for differences in adult size, even when early-germinating plants have as many as 35 days more for growth than late germinators. This, and the fact that differences occur even within single cohorts, implies that factors other than time of germination must influence plant size