The poetry of siegfried sassoon

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Non-visual variables in binocular performance

A Thesis presented to the Faculty of Science of the University of the Witwatersrand fo r the Degree of Doctor uf Philosophy. January 1979Clinical workers in binocular vision , known as o rth o p tis ts , have noticed variations in the binocular performance of patients which appear to have no relation to the ir visual state. Similarly there are some binocular tests, in p a rticu la r stereoscopic tests, which cannot be performed by normal students of the Optometry School. An in it ia l reading of the literature on binocular vision indicated that i t can be divided in to two parts, that concerning the mechanism which produces one visual percept from two visual inputs to the two separate eyes, and the mechanism which produces stereopsis, by evaluating the angular differences between the two re tin a l images and interpreting them as a sense of depth. I t was decided to concentrate on the haploscopic aspect of binocular vision , and to search fo r non-visual variables which determined the operation of th is function. A detailed reading of the lite ra tu re brought to lig h t several sets of experimental results showing marked v a ria b ility between normal subjects on the same te s t. Some of the operators commented on these, but did not look fo r th e ir o rig in . The neurological and neuro-anatomical lite ra tu re indicated that the production of the single visual percept was an on-going process which became more complex as i t was passed to higher neurological levels u n til the fin a l process was controlled by the cortex of the parietal lobe. This suggestion was confirmed by an E.F.G. programme carried out by the w rite r. The existence of neurological a c tiv ity in the parietal cortex involving the in h ib itio n processes which remove an unwanted diplopic image from visual perception suggested very strongly that psychological variables would be found here. This survey of the lite ra tu re also indicated that no previous work had been done in this fie ld and new tests had to be devised to isolate and measure the non-visual variables. This programme was undertaken by the w rite r who had done previous research in orthoptics and in optometry. These tests produced 20 scores, some of which suggested the psychological variable with which the optometric scores might correlate s ig n ific a n tly . The nature of these scores was described to a cross-discipline project team whose members designed a battery of tests, one psychological and the other neuro-psychological. The psychological battery was based on the assumption that the variable appeared to re late to some sort of psychological r ig id ity , but that as th is was not certain, certain other tests such as motivation, fru s tra tio n and suggestion must be adequately covered. The neuro-psychological battery assumed that the binocular variables must be measurable in the a c tiv ity of the central nervous system, and might appear as the muscular control of movement, or in the speeu of perception. A battery of te sts, including the E.E.G., was designed to measure these functions. The to ta l testing programme was now very large, and was given to two p ilo t samples. The battery was reduced in size by a study of the correlations, and by the use of cluster analysis. A study of the selected co rre la tio n between the binocular and the psychological scores indicated a relationship between the psychological results and some of the binocular tests. A reduced battery of both tests was given to a larger sample and a fa cto r analysis of the re su lt selected perseveration as the major psychological variable in binocular performance. During the course of the research work some very valuable discoveries were made fo r c lin ic a l optometry. The possible value of the results to psychology and the avenues of future research opened up by the programme of research are discussed

Preserving conformance for GCRA regulated flows

Traffic policing/shaping has been employed at the edge of networks to ensure proper provisioning of network resources and Quality of Service (QoS) guarantees. As shown in this thesis, however, network flows that have been regulated at the network edge based on traffic descriptors, e.g., GCRA, may still become non-conforming in the network core, depending on the packet scheduling algorithm used. Two supplemental schemes to scheduling algorithms are proposed and analyzed in this thesis to ensure conformance for GCRA regulated flows. The first scheme is to add an additional traffic regulator to shape the traffic more aggressively than required constraints before entering the scheduler. The second scheme explicitly computes the eligible departure time for the next packet of each flow in the scheduler. Performance achievable by both schemes, in terms of the percent non-conforming packets and the average delay, are investigated via simulation, when implemented for the First Come First Serve (FCFS) and the Weighted Fair Queuing (WFQ) schedulers

The Impact of Nordic Art in Europe 1878-1889

The period from 1878 to 1889 was one of increasing success for Nordic artists in Europe, particularly in Paris which was the accepted centre of the European art world at the end of the nineteenth century. Although there were early arrivals of Nordic students to study in Paris in the late 1860s, the main influx of Nordic artists occurred at the end of the 1870s, attracted by the Exposition Universelle of 1878 and the exhibition of French art that took place in Munich in 1879. Many Nordic artists undertook training at the Paris atelier of Léon Bonnat and the Académie Trélat where Bonnat corrected. The training they received was based around strong design skills, the importance of tone, and also of the composition as a whole entity. The art that was favoured at these studios were the Realist depictions of Millet, Courbet and Breton, and also Spanish masters such as Velázquez and Ribera. Erik Werenskiold came to Paris in 1881, and adopted a French juste-mileu style of Naturalism that took a middle position between the academic works of the Salon and the Impressionist avant-garde. In the three summers of 1883 to 1885, Werenskiold produced Peasant Burial, a work that portrayed the more prosperous Norwegian rural class as modern Europeans, concomitant with the achievement of their first political power. Werenskiold’s picture has far more in common with James Guthrie’s A Funeral Service in the Highlands than with the picture assumed to be its source, Burial at Ornans by Courbet. P. S. Krøyer received training with Bonnat, and quickly made his mark in Paris with depictions of rural working people. A poor reception in Denmark of his work The Italian Village Hatters led to Krøyer ensuring that future work was less open to the interpretation that it carried a political message. His depictions of fishermen at Skagen were supreme examples of his technical virtuosity, capturing light, texture and character. Edvard Munch and Vilhelm Hammershøi exhibited only six pictures between them outside Scandinavia in the 1880s. Munch met with negligible critical reaction to his two pictures, while Hammershøi, although receiving more mainstream critical attention, was not encouraged by his Parisian exhibition experience. Women artists faced particularly difficulties, particularly the ban on attending academies and life classes. Their strategies for coping with these problems included teaming up with fellow women artists to share studio and living space, and to provide a network of support that male artists took for granted. Harriet Backer and Kitty Kielland, Bertha Wegmann and Jeanna Bauck, are examples of two pairs of artists who engaged in this support structure. Nordic artists received many awards at the Paris Salon in the period 1878 to 1889, despite the bias towards French art that existed there. However, the art that was rewarded was produced using French techniques, and often - at least initially- French subjects. Later, the synthesis of French technique and Nordic subject matter provided many of the most technically-accomplished pictures of the period. Nordic art was received far more favourably at the Exposition Universelle of 1889 than that of 1878, exemplifying the great progress that had been achieved by Nordic artists in little more than a decade. The 1889 Exposition represented a high point for Naturalist Nordic art, and many important artists ceased exhibiting at the Salon after this date