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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Ground reaction forces and control of centre of mass motion during gait : implications for intervention in cerebral palsy

Gibbs, Sheila January 2014 (has links)
A question which has arisen clinically is the inability to generate adequate vertical force during the second half of the stance phase in cerebral palsy gait. Neither the mechanism nor the consequences of this inability are understood. It implies that the centre of mass (CoM) is inadequately supported with the potential for collapse of the limb in single support. Normal walking is achieved by the sophisticated control of the neuromuscular and skeletal systems with the purpose of advancing the body with minimum energy expenditure. These control systems are affected by damage to the brain in children with cerebral palsy and result in a multitude of problems which affect their gait making it difficult to determine cause and effect. This study aimed to improve the understanding of the ground reaction forces and motion of the CoM. Objectives The principle objectives were to analyse the supporting forces of the CoM during gait in normal adults, children, and children with diplegic cerebral palsy, by examining the inter-relationships of the vertical and horizontal components of the ground reaction force with the vertical component of motion and temporal parameters of the CoM. Design The study of adults and children’s data was both prospective and retrospective. The study of cerebral palsy data was retrospective. A new software programme was developed to extract specific gait parameters from both normal and cerebral palsy gait patterns. A novel approach to analyse the interaction of motion and force data in normal walking was subsequently developed. Background In normal gait, the vertical component of the ground reaction force forms a double hump where both humps are equal in magnitude and greater than body weight. It is widely accepted that the first hump (FZ1) is associated with deceleration of the downward motion of the CoM as the foot “impacts” the ground and the second hump (FZ2) is the action of “push off” as the body is propelled upwards and forwards. Walking requires force contributions from both legs but traditionally computed three-dimensional (3D) gait analysis packages presents the force data with both legs superimposed, rather than sequentially in time. This gives the impression that there is no period of overlap of the forces and thus ignores the critically important period where the CoM is transferred from one leg to the other during double support. By changing the presentation to view it sequentially in time, plus superimposing the CoM kinematics onto the same scale allowed their interactions to be observed and objectively measured. Methods The kinematic and kinetic data of 53 normal adults, 33 normal children, and 57 diplegic cerebral palsy children were acquired for the study. A new gait cycle, based on CoM motion, was defined to allow analysis of the forces in relation to CoM motion. Software was developed to extract specified parameters from the gait data. Impulse calculations over specific periods (based on the vertical motion of the CoM) allowed analysis of the vertical force contribution of each leg to the vertical support of the CoM. Results The results showed that inadequate generation of vertical force in children with diplegic cerebral palsy was widespread. In approximately 40% of such children there was a reduced ability to generate an adequate FZ2, which resulted in a reduced ability to control of the descent velocity of the CoM. The mean reduction in descent velocity in cerebral palsy was only 54% compared to 86% in adults. Integration of the vertical force and motion of the CoM showed that FZ2 was associated with controlling the descent velocity of the CoM. This reverses the traditionally accepted concept of “impact” and is contrary to the belief that FZ2 is associated with ‘push off’. Conclusions and Relevance This study emphasises the importance of the role of the supporting leg in the second half of stance. Failure to generate an adequate FZ2, which is currently ignored in clinical practice, should be given priority in patient management. This new knowledge has significant implications from a clinical perspective, not only in diplegic cerebral palsy, but in pathologies such as amputees, spina-bifida, and other neuro-muscular conditions.
272

Consolidation and structure of paper coating and fibre systems

Kugge, Christian January 2003 (has links)
Paper coatings or coating colours are high solidssuspensions that are applied to paper to improve chieflyprintability and optical properties. A paper coatingsuspension, including pigments, binders and thickeners, is acomplex system which must be understood if the end-useproperties of paper are to be improved. Some of the importantissues that need to be addressed are the mechanisms ofmigration of latices in a drying film, the influence ofthickener on the overall consolidation and the behaviour ofpaper coatings under compression.U nderstanding theconsolidation of paper coatings is essential as the aggregatestructures formed at this stage largely determine theperformance of the paper coating.Similarly, the forming ofpaper itself from pulp fibres requires a detailed understandingof the consolidation and dewatering process. In this thesis several approaches have been used in order tostudy the consolidation of paper coatings before and afterapplication to substrates. The techniques utilised arerheometry, centrifugation with NMR-imaging, scanning electronmicroscopy (SEM) and atomic force microscopy (AFM).Furthermore, investigations of the compressional rheology offibre systems has indicated that stepped pressure filtrationcan be a useful tool in the study of fibre dewatering. The primary findings presented in this thesis can besummarised as follows. Studies of the compressive yield stressand rheological properties of ground calcium carbonate (GCC)suspensions indicate that the addition of a commonly usedthickener can cause flocculation, most likely of a depletiontype, which leads to more compact structures during dewatering.When applied to substrates, migration and film formation ofbinder latices in the presence of calcium carbonate pigmentsand CMC thickeners occurs concurrently and collectively. Thisis shown to influence the consolidation of the top layer of thecoating to a great extent. It was found that CMC retards themigration of latices and that ethyl(hydroxyethyl)cellulose(EHEC) adsorbs to latex and creates a composite material uponlocal film formation. The composite retains an internalhoneycomb structure in the film, that is revealed by mapping ofelastic variations using AFM phase imaging. For fibre systems, the novel method of stepped pressurefiltration has been applied to study the compressional rheologyof pulp suspensions, and the effect of added surfactantsinvestigated. The technique is shown to be a promising tool forthe study of structure-dewatering relationships in fibresuspensions.
273

On the Behavioral Responses of Free Uinta Ground Squirrels to Trapping

Balph, David F. 01 January 1964 (has links)
Biologists often trap animals to obtain information on them. If trapping is selective toward some animals, the information may be inaccurate. Most mammalogists know or suspect that their trapping techniques (reviewed by Hayne, 1949; and Stickel, 1954) contain sources of bias. Since trapping remains the only feasible way to obtain information on many animals, researchers have tried to discover sources of sampling error and refine their techniques. They have found that one major source of difficulty may lie in the behavior of animals. Individual animals seem to respond differently to trapping, both initially and through learning (Geis, 1955; Crowcroft and Jeffers, 1961; and others). However, researchers seldom observe the behavioral responses of animals to traps. They infer information from capture data. Perhaps an empirical approach would shed more light on the relationship between behavior and trapping. The present study is such an approach. The study concerns the behavioral responses of adult Uinta ground squirrels, Citellus armatus, to trapping. I based the study on the direct observations of known individuals in a wild population. My primary objective was to learn how animals respond to a trap, to capture, and to recapture. My approach was both that of a population ecologist interested in factors affecting trapping success and that of a behaviorist interested in the effect of trapping procedures on the behavior of animals. I conducted a broad ecological and behavioral study of the population (Balph and Stokes, 1963) before beginning the research on trap response, which helped me select parameters and develop procedures. I also conducted a pilot study on deer mice, Peromyscus maniculatus, in the laboratory to test some procedures and the design of the trap-response investigation.
274

[An embryological study of the gopher (Citillus richardsonii)]

McNeill, Archie Kitchener 14 October 2009
The thesis is divided into four parts;<p> 1.The implantation of the blastodermic vesicle,<p> 2.The method of amnion formation in Citillus,<p> 3.The anatomy and foetal membranes of a 25 mm. embryo,<p> 4.The brain of a 9 mm. foetus.
275

Sensorimotor adjustments after unilateral spinal cord injury in adult rats

Webb, Aubrey Alan 25 August 2003
A variety of behavioural tests were used to examine both sensory and motor function of freely behaving unilaterally spinal cord-injured and uninjured rats. The first experiment was designed to determine whether sensory and motor differences existed between uninjured Fischer, Lewis, Long-Evans, Sprague-Dawley and Wistar rats using endpoint, quantitative kinematic, and kinetic measurements. The second experiment examined differences in sensorimotor responses to cervical spinal cord hemisection in Lewis, Long-Evans and Wistar rats. For the third experiment, reflex and locomotor abilities of unilateral cervical or thoracic spinal cord hemisected Long-Evans rats were determined using endpoint, semi-quantitative kinematic, and kinetic measurements. The fourth experiment was designed to investigate the importance of the rubrospinal tract and ascending dorsal column pathways to overground locomotion. This experiment was conducted to help explain the behavioural observations made following cervical spinal cord hemisection. Furthermore, this experiment examined the effects of combined unilateral rubrospinal and dorsal column injury on overground locomotion using endpoint and kinetic measurements. Finally, the fifth experiment set out to investigate the contribution of tracts running in the ventrolateral spinal cord on overground locomotion in freely behaving Long-Evans rats. These animals were assessed using endpoint and kinetic measurements. The results of these studies revealed that motor and sensory functions are not similar for all uninjured strains of rats. Specifically, Fischer rats tend to have considerable differences in their morphological features and sensorimotor abilities compared to the other strains examined. Results from the other experiments indicate that adult freely behaving female rats develop a characteristic gait when pathways important for locomotion are injured unilaterally, regardless of strain. The rubrospinal tract and ascending dorsal column pathways appear to be important for both skilled and flat-ground locomotion as well as forelimb use while rearing. Pathways traveling within the ventrolateral pathway, however, are not necessary or sufficient for locomotion or limb useage while rearing when injured by themselves. Animals with ventrolateral spinal funiculus injuries regain normal forelimb use and skilled locomotor abilities. Injury to the ventrolateral spinal funiculus, however, results in mild (compared to rubrospinal and dorsal column injured animals) yet long-lasting locomotor changes based on ground reaction force determination. These findings are in agreement with the current opinion that there is a substantial amount of functional redundancy of pathways traveling in the ventral and ventrolateral funiculi.
276

Sensorimotor adjustments after unilateral spinal cord injury in adult rats

Webb, Aubrey Alan 25 August 2003 (has links)
A variety of behavioural tests were used to examine both sensory and motor function of freely behaving unilaterally spinal cord-injured and uninjured rats. The first experiment was designed to determine whether sensory and motor differences existed between uninjured Fischer, Lewis, Long-Evans, Sprague-Dawley and Wistar rats using endpoint, quantitative kinematic, and kinetic measurements. The second experiment examined differences in sensorimotor responses to cervical spinal cord hemisection in Lewis, Long-Evans and Wistar rats. For the third experiment, reflex and locomotor abilities of unilateral cervical or thoracic spinal cord hemisected Long-Evans rats were determined using endpoint, semi-quantitative kinematic, and kinetic measurements. The fourth experiment was designed to investigate the importance of the rubrospinal tract and ascending dorsal column pathways to overground locomotion. This experiment was conducted to help explain the behavioural observations made following cervical spinal cord hemisection. Furthermore, this experiment examined the effects of combined unilateral rubrospinal and dorsal column injury on overground locomotion using endpoint and kinetic measurements. Finally, the fifth experiment set out to investigate the contribution of tracts running in the ventrolateral spinal cord on overground locomotion in freely behaving Long-Evans rats. These animals were assessed using endpoint and kinetic measurements. The results of these studies revealed that motor and sensory functions are not similar for all uninjured strains of rats. Specifically, Fischer rats tend to have considerable differences in their morphological features and sensorimotor abilities compared to the other strains examined. Results from the other experiments indicate that adult freely behaving female rats develop a characteristic gait when pathways important for locomotion are injured unilaterally, regardless of strain. The rubrospinal tract and ascending dorsal column pathways appear to be important for both skilled and flat-ground locomotion as well as forelimb use while rearing. Pathways traveling within the ventrolateral pathway, however, are not necessary or sufficient for locomotion or limb useage while rearing when injured by themselves. Animals with ventrolateral spinal funiculus injuries regain normal forelimb use and skilled locomotor abilities. Injury to the ventrolateral spinal funiculus, however, results in mild (compared to rubrospinal and dorsal column injured animals) yet long-lasting locomotor changes based on ground reaction force determination. These findings are in agreement with the current opinion that there is a substantial amount of functional redundancy of pathways traveling in the ventral and ventrolateral funiculi.
277

[An embryological study of the gopher (Citillus richardsonii)]

McNeill, Archie Kitchener 14 October 2009 (has links)
The thesis is divided into four parts;<p> 1.The implantation of the blastodermic vesicle,<p> 2.The method of amnion formation in Citillus,<p> 3.The anatomy and foetal membranes of a 25 mm. embryo,<p> 4.The brain of a 9 mm. foetus.
278

Ground Antennas for Slim Handsets

CHU, FANG-HSIEN 20 August 2012 (has links)
In this dissertation, multiband ground antennas for slim handsets are presented. The design techniques are on efficiently exciting the resonant modes of the system ground plane of the handset to greatly enhance the antenna¡¦s operating bandwidth. The first antenna design is a monopole antenna integrated with a slot antenna formed in a clearance in the system ground plane to enhance the bandwidth of the antenna¡¦s lower band for penta-band WWAN operation. The second antenna design uses a shaped circuit board with a proper notch embedded therein to result in stronger surface current excitation in the ground plane, which leads to bandwidth enhancement in the antenna¡¦s lower band and upper band. The second antenna design can cover seven-band WWAN/LTE operation. The antenna geometry in the second antenna design is further applied in the third antenna design. In order to meet the practical application of slim handsets, the third antenna design is integrated with a battery element and a metal midplate to decrease the thickness of the handset. The third antenna design can cover seven-band WWAN/LTE operation. Finally, the simulated SAR and HAC results are analyzed for the three proposed antennas.
279

Decreasing Variation in Cook Color of Ground Beef Patties Varying in Myoglobin and pH Using Acetic Acid and Hydrocolloid Solutions

Aldredge, Teresa Lynn 2009 December 1900 (has links)
The objective was to examine the use of acetic acid (AA) with xanthan gum (XG) or konjac flour (KF) to reduce variation in cooked color of ground beef patties varying in myoglobin and pH. Beef clods were selected from carcasses of young (<24 months, Y) and mature (>48 months, M) animals. Within each age category, high (>6.0, H) and normal pH (5.3-5.7, N) clods were chosen. Ground beef was prepared from each maturity/pH combination and treatments applied at 12% of the meat block: control (mixed only), 0.5% AA, 0.25% XG/0.5% AA, or 0.125% KF/0.5% AA. Dry and moist cooking was performed in a convection oven to internal temperatures: 65.6 degrees C, 71.1 degrees C, and 76.7 degrees C. Patties were held at 76.7 degrees C for up to 240 min in dry and moist environments. Internal (assessed at 0, 120, and 240 min of holding) and external (assessed every 30 min, 0 to 240 min of holding) color evaluations (CIE L*a*b*, visual doneness, and pink scores) were conducted. Three replications were performed. The YN patties had the most done appearance internally and the highest denatured myoglobin percentage. Generally, the YH and MN patties had responses between YN and MH got most variables. The MH patties had the highest internal a* color space values, lowest degree of doneness scores and low percentage of denatured myoglobin. The YN patties responded normally to the different internal temperatures achieved during cooking. The YH, MN, and MH patties had increased doneness to 71.1 degrees C and plateaued between 71.1 degrees C to 76.7 degrees C. Visual degree of doneness decreased during moist holding and this was most evident in dry cook/moist held patties. Patties from MH meat were not affected by the treatments as much as the other meat types. The inclusion of AA, XG/AA, and KF/AA in patties made from YH and MN can effectively reduce visible redness and increase myoglobin denaturation in comparison to the control YN beef patties. These ingredients could be viable options to reduce the variation that pH or myoglobin content imparts on ground beef patty cooked color, but as seen in the MH meat, treatment additions were not effective for overcoming both pH and high myoglobin content.
280

A New Broadband Electromagnetic Band-gap (EBG) Power Planes with High Suppression of Ground Bounce Noise

Chang, Sin-Min 28 April 2004 (has links)
In This Thesis , We primarily introduce some results with suppression of ground bounce noise in high-speed PCB by the formal researchers and summarize their advantages and weaknesses .In the next section .we explain why the EBG (Electromagnetic Band Gap ) design structure is from PBG (Photonic Band Gap ) concept in optical research field and that its principle can suppress GBN . We also summarize their advantages and weaknesses .In the following part, we define five parameters of EBG design structure to find the optimal solution by HFSS simulation method .The optimal solution can enlarge the bandwidth of suppression of GBN to 5.40GHz.We prove the accuracy of HFSS simulation method by actual measurement . When the EBG basic cell gradually compact from n=9.their characteristics are according to 1.central frequency towards high frequency 2.bandwidth of suppression of GBN is more broadband 3. forbiddance band depth becomes wider. Finally we oppose some new EBG design structures to solve some problems of old EBG design structure .These new EBG design structures can enhance signal integrity (SI) and law frequency response. Include three items 1.Meander design structure 2. Buddha design structure 3. Budder design structure .We also prove the accuracy of HFSS simulation method by actual measurement.

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