Computational aspects of the through-focus characteristics of the human eye

Calculating through-focus characteristics of the human eye from a single objective measurement of wavefront aberration can be accomplished through a range of methods that are inherently computationally cumbersome. A simple yet accurate and computationally effcient method is developed, which combines the philosophy of the extended Nijboer-Zernike approach with the radial basis function based approximation of the complex pupil function. The main advantage of the proposed technique is that the increase of the computational cost for a vector valued defocus parameter is practically negligible in comparison to the corresponding scalar valued defocus parameter

Factors Affecting Feeding Habits of Sheep Grazing Foothill Ranges of Northern Utah

An experiment was designed to study the effects of forage availability, season and intensity of grazing, and distribution and behavior of sheep on their forage preferences. Three grazing periods of 15 days each were used to study the effect of season. Each grazing period included a heavy and a moderate stocking intensity. Pastures were divided by a grid into 30.48 m x 30.48 m compartments. Each compartment was sampled for botanical composition of available herbage prior to and after grazing. Esophageally fistulated sheep were allowed to graze freely and positions of individual sheep with respect t o compartments were recorded at 5-minute intervals during the daily forage sample collection period. Immediately following collection of fistula samples, daily measurements were taken on leaf area index and height for all plant species. Estimates of aerbage yield and forage utilization were derived from heightleaf area measurements by regressions. Botanical composition of the diet was determined through microscopic analysis of plant cuticle fragments on dried, ground esophageal samples. Analysis of the dietary data indicated that season had no effect on the botanical composition of diets of sheep. However, grazing intensity significantly (P \u3c 0. 20) affected diets of sheep. Significant differences (P \u3c 0 . 01) were also found in proportion of plant species that comprised the diet at any particular time. Individual sheep were significantly (P \u3c 0.01) different in their forage preferences . There were no significant changes in botanical composition of the compartments due to grazing. However. bare ground increased significantly (P \u3c 0.10) more under heavy stocking than under moderate stocking. Herbage yield was found to be highly correlated with leaf area index and height (r2 = 0.85) in the ungrazed control pasture. Forage yield in the grazed pastures was a l so correl ated with leaf area index and height (r2= 0.79) . Utilization was estimated as the difference between the two parameters . Sheep were observed to graze more heavily around the periphery of shrubs than in the interspaces. The heavily grazed areas around shrubs were found to be significantly larger in heavily stocked pastures (P \u3c 0.10) . Observations of grazing behavior showed that sheep tended to orient themselves toward conspicuous objects . In so doing, they grazed a strip leading from one conspicuous object to another (ex. shrubs) . In an experiment designed to determine the role of such conspicuous objects in animal distribution and feeding behavior, sheep distribution, in relation to randomly-placed cardboard boxes. was found to be non-random and significantly (P \u3c 0.05) related to the position of the boxes. It was also found that sheep grazed the herbaceous species to a certain height below which the plants became inaccessible to grazing. Micro-associations of plant species greatly influenced preferences. Sagebrush (Artemisia tridentata) plants exerted a negative effect on use of adjacent bitterbrush (Purshia tridentata) plants. This negative effect was determined by the distance between the two shrubs. This critical distance was found to be 56.1 ± 23.7 cm and was not affected either by season or stocking intensity . An equation was developed by multiple regression to predict diets of grazing sheep. This equation explained 52% of the variation in botanical composition of the diet. Visual orientation of individual sheep, while grazing, modified to a large extent their forage preferences

An Approach to Range Inventory for the Annual Range Type of the Arid and Semi-Arid Regions of the Sudan

Range inventory, by definition, is the evaluation of the range resources to determine a proper and safe level of stocking and to provide a record of vegetation and vegetation changes (Stoddart and Smith, 1955). Range survey is defined by the Range Conservation Glossary, Soil Conservation Service (1944) as a systematic and comprehensive inventory and analysis of the range resources and related management problems of a range area for the purpose of developing plans of management therefrom. Accordingly, range inventory is the quest for basic information about rangelands and the development of guides and procedures for their management, improvement and efficient use

Range Improvement by Waterspreading in the Gash Delta, Kassala Province: Democratic Republic of the Sudan

The area north of latitude 14° north in the Sudan is characterized by unreliable precipitation patterns and a high incidence of a drouth period following the first rain of the rainy season. In this region it is not uncommon to have a completely dry year without a single rain shower. The damage occurring to the plant cover when a drouth period follows the first rain is great. This is especially the case for the annual plant species in that such precipitation distribution patterns tend to exhaust the seed supply in the soil and do not supply adequate moisture for seed germination. This factor has largely been responsible for development of sparse vegetal cover consisting mainly of shrubs with an occasional understory of early maturing annuals that are evident in years with a good rainy season

Enhancing accuracy and precision of transparent synthetic soil modelling

Over recent years non-intrusive modelling techniques have been developed to investigate soil-structure interaction problems of increasingly complex geometry. This paper concerns the development of a small-scale, 1 g, modelling technique using a transparent analogue for soil with particle image velocimetry for internal displacement measurement. Larger model geometry achieved in this research using fine-grained transparent synthetic soils has led to an increased need for rigorous photogrammetric correction techniques. A correction framework, based upon a modified version of the pinhole camera model, is presented that corrects for lens and camera movement induced errors as well as scaling from image space to object space. An additional statistical approach is also developed to enhance the system precision, by minimising the impact of increased non-coplanarity between the photogrammetry control plane and the target plane. The enhanced data correction and statistical precision is demonstrated using a case study examining the failure mechanism around a double helical screw pile installed in transparent synthetic soil representative of a soft clay

Update of Guidelines for laparoscopic treatment of ventral and incisional abdominal wall hernias (International Endohernia Society (IEHS)) : Part B

In 2014 the International Endohernia Society (IEHS) published the first international "Guidelines for laparoscopic treatment of ventral and incisional abdominal wall hernias". Guidelines reflect the currently best available evidence in diagnostics and therapy and give recommendations to help surgeons to standardize their techniques and to improve their results. However, science is a dynamic field which is continuously developing. Therefore, guidelines require regular updates to keep pace with the evolving literature. Methods For the development of the original guidelines all relevant literature published up to year 2012 was analyzed using the ranking of the Oxford Centre for Evidence-Based-Medicine. For the present update all of the previous authors were asked to evaluate the literature published during the recent years from 2012 to 2017 and revise their statements and recommendations given in the initial guidelines accordingly. In two Consensus Conferences (October 2017 Beijing, March 2018 Cologne) the updates were presented, discussed, and confirmed. To avoid redundancy, only new statements or recommendations are included in this paper. Therefore, for full understanding both of the guidelines, the original and the current, must be read. In addition, the new developments in repair of abdominal wall hernias like surgical techniques within the abdominal wall, release operations (transversus muscle release, component separation), Botox application, and robot-assisted repair methods were included. Results Due to an increase of the number of patients and further development of surgical techniques, repair of primary and secondary abdominal wall hernias attracts increasing interests of many surgeons. Whereas up to three decades ago hernia-related publications did not exceed 20 per year, currently this number is about 10-fold higher. Recent years are characterized by the advent of new techniques-minimal invasive techniques using robotics and laparoscopy, totally extraperitoneal repairs, novel myofascial release techniques for optimal closure of large defects, and Botox for relaxing the abdominal wall. Furthermore, a concomitant rectus diastasis was recognized as a significant risk factor for recurrence. Despite still insufficient evidence with respect to these new techniques it seemed to us necessary to include them in the update to stimulate surgeons to do research in these fields. Conclusion Guidelines are recommendations based on best available evidence intended to help the surgeon to improve the quality of his daily work. However, science is a continuously evolving process, and as such guidelines should be updated about every 3 years. For a comprehensive reference, however, it is suggested to read both the initially guidelines published in 2014 together with the update. Moreover, the presented update includes also techniques which were not known 3 years before