Effect of wall thickness on radiation from circular waveguides

An experimental study shows that the thickness of a circular waveguide wall greatly affects its radiation characteristics. The exact solution of Weinstein for infinitely thin walls appears in practice to be valid only when the wall thickness is less than 0.01 ?.     

Software implementation of online risk-based security assessment

This paper describes software implementation for online risk-based security assessment which computes indices based on probabilistic risk for use by operators in the control room to assess system security levels as a function of existing and near-future network conditions. The paper focuses on speed enhancement techniques that are essential for online application and result visualization methods that offer clear and meaningful ways to enhance human assimilation and comprehension of security levels. Results of testing on a series of 1600 bus power flow models retrieved from the energy management system of a large US utility are presented and serve to illustrate the benefits of the software.     

Local gain control and focal accommodation in the Self Similar Stack vision model

The aim of this paper is to report an extension to the computationally efficient Self Similar Stack model (Burton et al. Biol., Cybernet. 53, 397-403, 1986) to include the effects of local gain control in the retina. The method employed to do this has been to fit a family of difference-of-Gaussian functions to the human contrast sensitivity function curves of van Nes and Bouman (J. Opt. Soc. Am. 57, 401-406, 1967). The centre frequencies of the DoGs within each family are octave-related, in a simplified manifestation of the DoG channels found by Wilson et al. (Vision Res. 23, 873-882, 1983). The sensitivity of each level, or channel, that formed the original Stack model is modulated individually according to the fitted values, as the local illumination varies within an image. The model was tested against psychometric data obtained by Haig and Burton (Appl. Optics 26, 492-500, 1987) during experiments on visual discrimination. The consistency of the results indicates the validity of the approximations and the robustness of the model, either for machine vision purposes or for predicting human visual performance. A simple algorithm, developed for use with a machine vision application of this model, provides a means by which a TV camera may be focused automatically. The success of this algorithm, using the newly computed channel sensitivities, suggests that human focal accommodation may be regulated by a similar form of mechanism.     

Anterior communicating artery aneurysm rupture: an unusual cause of acute subdural hemorrhage

A case of acute subdural hemorrhage caused by rupture of an anterior communicating artery aneurysm is presented. The patient is a young man who presented with an acute onset of neurologic symptoms; computed tomography revealed subdural hemorrhage in the absence of associated subarachnoid or intraparenchymal bleeding.     

Changes to acoustic communication systems in human-altered environments.

Animal communication systems have become closely tuned to local habitat conditions as populations have adjusted to different long-term environmental pressures. However, many habitats are now rapidly changing because of anthropogenic modification. Maintenance of effective communication systems in greatly altered environments will depend on communicative responses on both evolutionary and ontogenetic time scales. Consideration of potential acoustic challenges caused by human-generated habitat modification has important implications for basic research and conservation biology. First, the observed signal structure of individuals in altered environments may not match the normally hypothesized call structure. Second, species that either possess little ability to adapt quickly on an evolutionary time scale or have little plasticity in their communicative systems may be unable to respond to large anthropogenic alterations in their acoustic environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gastric wounds: study of 85 patients

During January 1987 and December 1990 we studied 85 patients (75 males), the age varying between 6 and 47 years (mean 27.6) sustaining penetrating (81 patients) and blunt (4 patients) gastric wounds. The mortality rate was 17.6% (15 patients) with four deaths occurring during the surgical procedure as consequence of critical associated injuries. Only one death happened as consequence of gastric wound; 6 patients died during the first 24 hours of hospitalization because of irreversible shock, 9 deaths came about after the first day of hospitalization (4 sepsis, 3 respiratory failure, 2 head trauma). The morbidity rate among the 81 patients that survived after surgical treatment was 39.5% (32 patients). The main postoperative gastric complication was vomiting in 10 patients (5 presenting vagus nerve injury and 5 sustaining pancreatic and/or another hollow viscus wounds) one patient presented with gastric suture dehiscence. Among the 12 patients sustaining vagus nerve injury the presence of gastric complication was higher in the group that was not submitted to pyloroplasty (6 patients). Analysing the patients presenting gastric and pancreatic injuries we verified that morbidity rate was statistically significantly higher in this group (69.2%) than in overall morbidity (39.5%).