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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.
81

Interaction of cocaine with some central dopominergic and serotonergic mechanisms

Berman, Mark Harold 01 January 1980 (has links)
The present study ln male Wistar rats was designed to rate and analyze six specific cocaine-induced behaviors. These behavioral parameters have been defined by others as either dopaminergic (sniffing, grooming, and locomotor activity) or serotonergic (repetitive head movements, rearing, and Straub tail) in origin. Results were analyzed by analysis of variance in two ways : (i) as grouped dopaminergic or serotonergic scores, and (ii) as the net behavioral index (dopaminergic scores minus the serotonergic scores). The purpose of approaching the data in this way was to attempt to define the behavioral interactions of the two neurotransmitters. One conclusion that developed from this study was the indication that dopaminergic behaviors peak at lower doses of cocaine than do serotonergic behaviors. This relationship held true for all the individual parameters in addition to the dopaminergic and serotonergic totals. A dopaminergic blocker, haloperidol, significantly attenuated all responses elicited by cocaine. When the net behavioral index was analyzed, it was found that the response of the median dose of cocaine was significantly altered from a net dopaminergic score towards a net serotonergic score. In this sense, haloperidol was shown to have the capacity to attenuate dopaminergic-associated parameters to a greater extent than the serotonergic-associated parameters. Cyproheptadine, an antiserotonergic agent, did not significantly affect the net behavioral index; however, this compound did significantly increase the dopaminergic parameter of grooming at the high doses of cocaine and cyproheptadine. Also at this dose combination , gnawing was elicited -- a dopaminergic response seen under no other experimental conditions. Due to the antiserotonergic agent causing an increase in the dopaminergic parameters of grooming and gnawing, it is proposed that the serotonergic influence on these two dopaminergic behaviors is of an inhibitory type.
82

Manipulátor se vzorky plechů pro mechanické zkoušky / Manipulator with sheet metal samples for mechanical tests

Glogar, Matěj January 2010 (has links)
This thesis deals with a solution of lifting equipment for sheet metal samples handling. Facility will be part of an automatic production line for semi-finished test specimens for testing the mechanical properties of sheet metals. The options of solutions discussed in this thesis is performed that choice which should be the concept of lifting equipment. Course work cycle of the selected concept is designed, so that material flow provided by the facility meets requirements of the production line. Calculations for the design parts of the main cylinder and the running gear are carried out using a set of parameters and then strength check of steel construction follows. The 3D model of the manipulator, the manipulator assembly drawings and layout drawings of the production line are annexes of this work.
83

Exploration of Constant-Force Wristbands for a Wearable Health Device

Naylor, Thomas Alexander 27 July 2021 (has links)
Wearable Health Devices (WHDs) are an emerging technology that enables continuous monitoring of vital signs during daily life. Issues with constant and consistent data acquisition have been found while WHD technology has developed. The force of the measurement area and movement of the sensors are key mechanical issues that need to be solved for WHDs to become a viable way to continuously monitor health conditions. This work explores Constant-Force Mechanisms (CFMs) as a solution to problems the current WHD industry faces. Additionally, the relationship between force provided from the mechanism, sensor pressure on the wrist, patient comfort, and sensor readings quality are explored and analyzed. Design requirements for a constant-force wristband were narrowed down to seven critical requirements (mechanism size vs. allowable travel, ability to be used on a curved surface, works well with existing clasps, ease of assembly, direction of travel, material, and force generation). These key requirements need to be considered for a WHD with an integrated CFM to be designed successfully. Two main concepts (buckling beams and tape springs) were prototyped and evaluated against the seven key requirements. The design and testing of a wrist worn sensing band used to gather relationship data among band tension, sensor pressure, patient comfort, and pulsatile signal quality is also presented. Human subject testing (IRB2020-268) was performed on a wristband with an integrated CFM and the wrist worn sensing band that were developed. The band with an integrated CFM compared pressure on the wrist for both a band with and without an integrated CFM for eight different movement activities. On average the band with the integrated CFM had a lower coefficient of variation for all except one of the activities. The data collected from the wrist worn sensing band shows that tension varies linearly with pressure, and that the pressure vs. tension slope increases with increasing wrist width. There also exists a linear relationship between tension and patient pain/comfort, but pressure does not show an effect on the patient discomfort or pain experienced. Signal quality when measured in the range of of 0-4 N and 0-20 kPa does not have a direct correlation to either tension or pressure.
84

Designing Developable Mechanisms on Conical and Cylindrical Developable Surfaces

Hyatt, Lance Parker 10 June 2020 (has links)
The research results presented in this thesis provide tools and methods to aid in the design of developable mechanisms. This work will help engineers design compact mechanisms onto developable surfaces, making it possible for them to be used in future applications. The thesis introduces terminology and definitions to describe conical developable mechanisms. Models are developed to describe mechanism motion with respect to the apex of the conical surface, and connections are made to cylindrical developable mechanisms using projected angles. The Loop Sum Method is presented as an approach to determine the geometry of the cone to which a given spherical mechanism can be mapped. A method for position analysis is presented to determine the location of any point along the link of a mechanism with respect to the conical geometry. These methods are also applied to multiloop spherical mechanisms. This work created tools and methods to design cylindrical and conical developable mechanisms from flat, planar patterns. Equations are presented that relate the link lengths and link angles of planar and spherical mechanisms to the dimensions in a flat configuration. These flat patterns can then be formed into curved, developable mechanisms. Guidelines are established to determine if a mechanism described by a flat pattern can exhibit intramobile or extramobile behavior. A developable mechanism can only potentially exhibit intramobile or extramobile behavior if none of the links extend beyond half of the flat pattern. The behavior of a mechanism can change depending on the location of the cut of the flat pattern. Different joint designs are discussed including lamina emergent torsional (LET) joints. It is shown that developable mechanisms on regular cylindrical surfaces can be described using cyclic quadrilaterals. Mechanisms can exist in either an open or crossed configuration, and these configurations correspond to convex and crossed cyclic quadrilaterals. Using equations developed for both convex and crossed cyclic quadrilaterals, the geometry of the reference surface to which a four-bar mechanism can be mapped is found. Grashof mechanisms can be mapped to two surfaces in open or crossed configurations. The way to map a non-Grashof mechanism to a cylindrical surface is in its open configuration. Extramobile and intramobile behavior can be achieved depending on selected pairs within a cyclic quadrilateral and its position within the circumcircle. Selecting different sets of links as the ground link changes the potential behavior of the mechanism. Different cases are tabulated to represent all possibilities.
85

Sympathetic activation and heart failure

Badenhorst, Danelle 05 March 2008 (has links)
ABSTRACT Chronic activation of the sympathetic nervous system, via β-adrenoreceptor (AR) stimulation, contributes toward progressive heart failure. However, in this regard there are some outstanding issues which require clarity. First, in addition to contributing toward progressive heart failure, it is not clear whether chronic β-AR activation can also initiate cardiac decompensation. If so, the mechanisms of this effect also need to be determined. Second, the role of functional variants of β-AR genes as determinants of either the development or progression of heart failure requires elucidation. Moreover, whether there is any practical value in genotyping of patients for these variants has yet to be determined. These questions were addressed in the present thesis. With respect to the question of whether chronic β-AR activation initiates cardiac decompensation, the mechanisms responsible for the transition from compensated cardiac hypertrophy to heart failure in pressure overload states, such as hypertension, are uncertain. In this thesis I explored whether chronic sympathetic nervous system activation, produced by daily administration of a β-AR agonist, could promote the transition to cardiac pump failure in spontaneously hypertensive rats (SHR) with compensated cardiac hypertrophy. After 5 months of daily administration of a β-AR agonist, SHR developed marked left ventricular pump dysfunction, whereas normotensive control rats maintained pump function. The pump dysfunction noted in SHR was attributed to marked chamber dilatation with wall thinning, whilst myocardial contractile function appeared to be intact. The changes in cardiac structure and function noted after chronic β-AR activation in SHR were similar to those noted in SHR with advanced heart failure. These data provided the first evidence to indicate that chronic β- AR activation can promote the transition to decompensated cardiac hypertrophy in pressure overload states, and that this effect is principally mediated by adverse structural remodeling of the cardiac chamber. iii The mechanisms responsible for the effect of chronic β-AR activation on cardiac chamber dilatation were subsequently studied. The identified mechanisms included activation of an enzyme that degrades myocardial collagen (matrix metalloproteinase 2) and an increase of myocardial collagen of the type that is susceptible to collagen degradation (non-cross-linked collagen). I also excluded alternative potential mechanisms such as necrosis, apoptosis and an accumulation of type III collagen. However, previous studies have indicated that increases in myocardial collagen concentrations determine myocardial stiffness and not cardiac chamber dilatation. Hence, I performed a study to examine whether the impact of increases in myocardial collagen concentrations on cardiac structure and function depends on the qualitative changes in myocardial collagen. Indeed, using a variety of models of pressure overload hypertrophy associated with increases in myocardial collagen concentrations, I was able to provide evidence to support the theory that increases in myocardial collagen of the cross-linked phenotype will promote myocardial stiffness, whereas increase in myocardial collagen of the non-cross-linked phenotype promotes cardiac dilatation. With respect to the question of whether functional variants of β-AR genes contribute toward either the development or progression of heart failure, I studied the role of both functional β1-AR and β2-AR (together with a α2C-AR) gene variants in black South Africans with idiopathic dilated cardiomyopathy (IDC). In a prospective study I obtained data to indicate that the relationship between functional β2-AR genotypes and the progression to hospitalization, death or transplantation; a reduced exercise capacity, and left ventricular functional responses to b-blocker therapy, as described by other groups, is unlikely to be attributed to an independent effect of genotype on cardiac chamber dimensions and pump function. Moreover, I was able to show that contrary to what had previously been suggested, genotyping black subjects for functional α2C-AR iv and β1-AR gene variants is of little use when predicting the development or severity of IDC in this population group.
86

Expanding Lamina Emergent Mechanism (LEM) Capabilities: Spherical LEMs, LEM Joints, and LEM Applications

Wilding, Samuel E. 11 August 2011 (has links) (PDF)
Lamina Emergent Mechanisms (LEMs) are a class of compliant mechanisms that can be manufactured from sheet goods and possess motion out of the plane of fabrication. LEMs can be designed to perform sophisticated motions. This thesis expands LEM understanding and increases the ability to utilize them in applications by introducing the fundamentals of spherical LEMs, creating joints suitable for LEMs, and providing an example of a LEM application. In this thesis, the fundamentals of spherical LEMs are developed. This includes classification of all possible spherical 4R LEMs and a discussion of the motion characteristics of the various mechanisms. The motion characteristics associated with spherical 4R LEMs are then used to predict the motion of spherical 6R LEMs and arrays of spherical LEMs. Multiple spherical LEM prototypes are shown and discussed. A common difficulty of working with compliant mechanisms, especially LEMs, is creating suitable joints. There is often a trade off between flexibility in the desired direction of deflection, and stiffness in directions of undesired deflection. For this thesis, LEM joints that possess higher off-axis stiffness, especially in tension and compression, than previous designs were developed: the I-LET, the T-LET, and the IT-LET. Joint geometries were optimized and then modeled in commercial finite element analysis (FEA) software capable of nonlinear analysis. These models were used to predict the bending of tensile/compressive stiffnesses of the joints. As a benchmark, lamina emergent torsional (LET) joints were modeled and optimized for maximum tension and compression loading while maintaining the same bending stiffness as the joint being compared. Mechanisms that utilized the new joints were created and are briefly discussed. The use of these joints allows for minimized parasitic motion under tension and compression loads and expands the capability of LEM joints. The Lens Lift™ was developed to demonstrate an application of LEMs. The Lens Lift™ is a LEM device that allows for easier and more sterile use of disposable contact lenses. It possesses a monolithic structure and can be fabricated using simple manufacturing processes. As the contact lens user opens the blister pack used to store the lens, the lens is lifted out of the pack and presented to the user. The user can then lift the lens with one touch and place it in the eye. A provisional patent has been filed for the device and the device currently being evaluated by a major contact lens manufacturer for further development.
87

A Study of Action Origami as Systems of Spherical Mechanisms

Bowen, Landen A. 02 July 2013 (has links) (PDF)
Origami, the Japanese art of paper folding, has been used previously to inspire engineering solutions for compact, deployable designs. Action origami, the subset of origami dealing with models designed to move, is a previously unexplored area for engineering design solutions that are deployable and have additional motion in the deployed state. A literature review of origami in engineering is performed, resulting in seven key areas of technical origami literature from a wide variety of disciplines. Spherical mechanisms are identified as the method by which most action origami models achieve complicated motion while remaining flat-foldable. The subset of action origami whose motion originates from spherical mechanisms is termed "kinematic origami''. Action origami is found to contain large coupled systems of spherical mechanisms. All possible action origami models are classified by their spherical mechanism structure, resulting in eight possible categories. Viewing action origami as spherical mechanisms allows the use of established equations for kinematic analysis. Several kinematic origami categories are used to demonstrate a method for the position analysis of coupled systems of spherical mechanisms. Input-output angle relationships and coupler link motions are obtained for a single spherical mechanism, two spherical mechanisms coupled together, and four spherical mechanisms coupled in a loop arrangement. This lays a groundwork from which it is possible to create compact, deployable mechanisms with motion in the deployed state.
88

An Investigation of the Relation Between Remembering and Learning

Gabel, Charles Paul 07 1900 (has links)
<p>Remembering requires an awareness of prior occurrence. In contrast, learning is indicated by savings on performing a task; no awareness of prior occurrence is necessary. Previous research has shown that performance on measures of learning can be functionally and statistically dissociated from performance on remembering tasks. Some investigators have concluded that these dissociations indicate that there are separate memory systems. The experiments performed in this thesis investigate the alternative explanation that dissociations between measures of memory result because of differing retrieval requirements. Whereas previous experiments employed learning and remembering tasks that were mismatched in their reliance on conceptual processes, the present experiments employ a learning task that focuses on the conceptual relations between words.</p> <p>Meaningfulness of study processing was manipulated by requiring categorization of word pairs as similar or dissimilar. When the same categorization was performed at transfer, learning was of greater magnitude and of longer duration for more meaningfully related words. When repeated words were categorized by different attributes virtually no learning was observed. Therefore, in contrast to other research (e.g., Jacoby & Dallas, 1981), the meaningfulness and context of processing words were important determinants of learning.</p> <p>The relation between remembering and savings on categorization was investigated by requiring a recognition decision after each categorization at transfer. Effects on recognition paralleled those on categorization. Better recognition performance was observed for more meaningfully related words and for words repeated in the same task context. Discrimination of task context also was better for more meaningfully related words. Therefore, the effect of equating processing requirements between measures was to produce a functional dependence between remembering and learning. A statistical dependence between measures also was obtained. At transfer, faster than average categorizations were associated with "old" recognition decisions in conditions in which subjects based their recognition decision on familiarity only. However, the conclusion of statistical association is tentative because the requirement to recognize after categorization interfered with categorization.</p> <p>Manipulations of retrieval processes were successful in converting dissociations into associations. Therefore, this investigation supports the differing retrieval requirements explanation of dissociations between measures of memory.</p> / Doctor of Philosophy (PhD)
89

Traumatic injury among females: does gender matter?

El-Menyar, Ayman, El-Hennawy, Hany, Al-Thani, Hassan, Asim, Mohammad, Abdelrahman, Husham, Zarour, Ahmad, Parchani, Ashok, Peralta, Ruben, Latifi, Rifat January 2014 (has links)
BACKGROUND:Trauma remains one of the leading causes of morbidity and mortality worldwide. Generally, the incidence of traumatic injuries is disproportionately high in males. However, trauma in females is underreported.AIM:To study the epidemiology and outcome of different mechanisms and types of traumatic injuries in women.METHODS:We conducted a traditional narrative review using PubMed, MEDLINE and EMBASE, searching for English-language publications for gender-specific trauma between January 1993 and January 2013 using key words "trauma", "gender", "female" and "women".RESULTS:Among 1150 retrieved articles, 71 articles were relevant over 20 years. Although it is an important public health problem, traumatic injuries among females remain under-reported.CONCLUSION:There is a need for further research and evaluation of the exact burden of traumatic injuries among females together with the implementation of effective community based preventive programs.
90

Feeding behavior and serotonin metabolism in diet-induced obese rats

梁詠蓮, Leung, Wing-lin, Winny. January 2000 (has links)
published_or_final_version / Zoology / Doctoral / Doctor of Philosophy

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