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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.
41

Towards an Understanding of Prolonged Pronation: Implications for Medial Tibial Stress Syndrome and Achilles Tendinopathy

Becker, James N. M., 1979- 03 October 2013 (has links)
Epidemiologic data suggest 25% to 75% of all runners experience an overuse injury each year. Commonly cited biomechanical factors related to overuse injuries such as Achilles tendinopathy or medial tibial stress syndrome include excessive amounts or velocities of foot pronation. However, there is conflicting evidence in the literature supporting this theory. An alternative hypothesis suggests it is not necessarily the amount or velocity of pronation which is important for injury development; rather it is the duration the foot remains in a pronated position throughout stance that is the important variable. This project examined this hypothesis by first identifying biomechanical markers of prolonged pronation. Second, it assessed whether individuals currently symptomatic with injuries typically attributed to excessive pronation instead demonstrate the biomechanical markers of prolonged pronation. Finally, musculoskeletal modeling techniques were used to examine musculotendinous kinematics in injured and healthy runners, as well as healthy runners with prolonged pronation. The results suggest the two most robust measures for identifying individuals with prolonged pronation are the period of pronation and the eversion of the rear foot at heel off. Individuals with prolonged pronation can also be identified with a set of clinically feasible measures including higher standing tibia varus angles, reduced static hip internal rotation range of motion, and increased hip internal rotation during stance phase. Finally, individuals with prolonged pronation display a more medially located center of pressure trajectory during stance. Compared to healthy controls, individuals currently symptomatic with Achilles tendinopathy or medial tibial stress syndrome did not differ in the amount or velocity of pronation. However, they did demonstrate the biomechanical markers of prolonged pronation. Injured individuals also demonstrated greater average musculotendinous percent elongation than healthy controls, especially through mid and late stance. Currently healthy individuals demonstrating prolonged pronation exhibited musculotendinous percent elongations intermediate to the healthy and injured groups. As a whole, the results from this study suggest prolonged pronation may play a role in the development of common overuse running injuries. It is suggested future studies on injury mechanisms consider pronation duration as an important variable to examine. This dissertation includes unpublished co-authored material.
42

Presentation av visualiseringsföretag i regionen Norrköping/Linköping / Presentation of visualization companies in the Norrköping/Linköping region

Törnvall, Jenny January 2003 (has links)
<p>Den här rapporten är en kartläggning av klustret Vetenskaplig och Medial visualiseringsteknik. Jag har på uppdrag av Näringslivskontoret i Norrköping och E.S.D.A i Linköping intervjuat ett antal företag som arbetar med visualiseringsteknik. Frågorna har bland annat rört företagens sysselsättning/produkt och framtida planer för verksamheten. De flesta företagen har vänt sig mot nöjesindustrin och då främst spelbranschen men en del har arbetat med vetenskaplig forskning med medicinsk inriktning. </p><p>Alla tror på en framtid med visualiseringstekniken även om den svenska marknaden för en del är för liten och samtliga har svarat att det finns gott om kompetent arbetskraft på området. Detta medför att de flesta ser positivt på det egna företagets möjligheter till att expandera och växa. </p><p>I slutet av rapporten finns mina egna tankar om hur jag tror att framtiden kommer att utvecklas. Jag tror att visualiseringstekniken är här för att stanna och att vi har sett långt ifrån alla möjligheter som tekniken innebär. Campus Norrköping har medfört att flera nya småföretag som sysslar med visualiseringsteknik har startats och förhoppningsvis kommer det i framtiden att medföra att stora delar av marknaden kommer att förflyttas hit till Norrköping vilket skulle vara mycket positivt för kommunens näringsliv.</p>
43

Investigating the Boundaries of Feature Conjunction Representations in the Perirhinal Cortex

Douglas, Danielle 21 November 2012 (has links)
Convergent evidence suggests that the perirhinal cortex (PRC) is involved in perception, in addition to long-term memory, by representing higher-order object feature conjunctions. Recent functional magnetic resonance imaging (fMRI) investigations have shown greater PRC activity during the processing of objects with a higher versus lower degree of features in common, but notably, these studies have been limited to examining only two levels of feature overlap. To address this, we scanned neurologically healthy participants with fMRI during a 1-back working memory task for objects that possessed a very low, low, medium or high degree of feature overlap. Somewhat consistent with previous findings, trends towards greater PRC activity for high versus medium feature overlap objects, and for semantically identical compared to semantically different objects were observed. However, other aspects of our data, including diminished PRC activity during medium versus low feature overlap objects, are difficult to interpret and require further investigation.
44

Investigating the Boundaries of Feature Conjunction Representations in the Perirhinal Cortex

Douglas, Danielle 21 November 2012 (has links)
Convergent evidence suggests that the perirhinal cortex (PRC) is involved in perception, in addition to long-term memory, by representing higher-order object feature conjunctions. Recent functional magnetic resonance imaging (fMRI) investigations have shown greater PRC activity during the processing of objects with a higher versus lower degree of features in common, but notably, these studies have been limited to examining only two levels of feature overlap. To address this, we scanned neurologically healthy participants with fMRI during a 1-back working memory task for objects that possessed a very low, low, medium or high degree of feature overlap. Somewhat consistent with previous findings, trends towards greater PRC activity for high versus medium feature overlap objects, and for semantically identical compared to semantically different objects were observed. However, other aspects of our data, including diminished PRC activity during medium versus low feature overlap objects, are difficult to interpret and require further investigation.
45

Dissociable Influence of Reward and Punishment Motivation on Declarative Memory Encoding and its Underlying Neurophysiology

Murty, Vishnu Pradeep January 2012 (has links)
<p>Memories are not veridical representations of the environment. Rather, an individual's goals can influence how the surrounding environment is represented in long-term memory. The present dissertation aims to delineate the influence of reward and punishment motivation on human declarative memory encoding and its underlying neural circuitry. Chapter 1 provides a theoretical framework for investigating motivation's influence on declarative memory. This chapter will review the animal and human literatures on declarative memory encoding, reward and punishment motivation, and motivation's influence on learning and memory. Chapter 2 presents a study examining the behavioral effects of reward and punishment motivation on declarative memory encoding. Chapter 3 presents a study examining the neural circuitry underlying punishment-motivated declarative encoding using functional magnetic resonance imaging (fMRI), and compares these findings to previous studies of reward-motivated declarative encoding. Chapter 4 presents a study examining the influence of reward and punishment motivation on neural sensitivity to and declarative memory for unexpected events encountered during goal pursuit using fMRI. Finally, Chapter 5 synthesizes these results and proposes a model of how and why motivational valence has distinct influences on declarative memory encoding. Results indicated that behaviorally, reward motivation resulted in more enriched representations of the environment compared to punishment motivation. Neurally, these motivational states engaged distinct neuromodulatory systems and medial temporal lobe (MTL) targets during encoding. Specifically, results indicated that reward motivation supports interactions between the ventral tegmental area and the hippocampus, whereas, punishment motivation supports interactions between the amygdala and parahippocampal cortex. Together, these findings suggest that reward and punishment engage distinct systems of encoding and result in the storage of qualitatively different representations of the environment into long-term memory.</p> / Dissertation
46

Exploring Arterial Dynamics and Structures in IntraVascular UltraSound Sequences

Hernàndez i Sabaté, Aura 07 July 2009 (has links)
Les malalties cardiovasculars són una de les principals causes de mortalitat als països desenvolupats. La majoria d'elles són degudes a malalties arterials (especialment les coron ries), que vénen causades per l'acumulació de placa. Aquesta patologia estreny el flux sanguini (estenosi) i afecta les propietats elàstiques i bio-mecàniques (arteriosclerosi) de les artèries. En les últimes dècades, l'Ecografia Intra-Coronària (EIC) ha esdevingut una tècnica usual de diagnòstic per la imatge i seguiment de les malalties coronàries. L'EIC està basada en un cateterisme que mostra una seqüència d'imatges corresponents a seccions de l'artèria sota estudi. La inspecció visual de cadascuna d'aquestes imatges proporciona informació sobre el percentatge d'estenosi, mentre que la inspecció de les vistes longitudinals propociona informació sobre les propietats bio-mecàniques, que pot prevenir un desenllaç fatal de la malaltia cardiovascular. Per una banda, la dinàmica arterial (deguda al batec del cor, entre d'altres) és un dels principals artefactes per poder explorar les propietats biomecàniques. Al mateix temps, les mesures manuals d'estenosi requereixen un traçat manual de les vores del vas, tasca feixuga que consumeix molt de temps i que pot patir variabilitat entre observadors.Aquesta tesi proposa vàries eines de processament d'imatge per explorar la dinàmica de les artèries i les seves estructures. Presentem un model físic per extreure, analitzar i corregir la dinàmica rígida transversal dels vasos i per recuperar la fase cardíaca. A més, introduïm un mètode estadístic-determinista per a la detecció automàtica de les vores del vas. En particular, l'enfoquem a segmentar l'adventícia. Un protocol de validació acurat per assegurar una aplicació clínica fiable dels mètodes és un pas crucial en qualsevol proposta d'algorisme. En aquesta tesi tenim especial cura de dissenyar protocols de validació per a cadascuna de les tècniques proposades i contribuïmm a la validació de la dinàmica in vivo amb un indicador objectiu i quantitatiu per mesurar la quantitat de moviment suprimida. / Cardiovascular diseases are a leading cause of death in developed countries. Most of them are caused by arterial (specially coronary) diseases, mainly caused by plaque accumulation. Such pathology narrows blood flow (stenosis) and affects artery bio-mechanical elastic properties (atherosclerosis). In the last decades, IntraVascular UltraSound (IVUS) has become a usual imaging technique for the diagnosis and follow up of arterial diseases. IVUS is a catheter-based imaging technique which shows a sequence of cross sections of the artery under study. Inspection of a single image gives information about the percentage of stenosis. Meanwhile, inspection of longitudinal views provides information about artery bio-mechanical properties, which can prevent a fatal outcome of the cardiovascular disease. On one hand, dynamics of arteries (due to heart pumping among others) is a major artifact for exploring tissue bio-mechanical properties. On the other one, manual stenosis measurements require a manual tracing of vessel borders, which is a time-consuming task and might suffer from inter-observer variations.This PhD thesis proposes several image processing tools for exploring vessel dynamics and structures. We present a physics-based model to extract, analyze and correct vessel in-plane rigid dynamics and to retrieve cardiac phase. Furthermore, we introduce a deterministic-statistical method for automatic vessel borders detection. In particular, we address adventitia layer segmentation. An accurate validation protocol to ensure reliable clinical applicability of the methods is a crucial step in any proposal of an algorithm. In this thesis we take special care in designing a validation protocol for each approach proposed and we contribute to the in vivo dynamics validation with a quantitative and objective score to measure the amount of motion suppressed.
47

Neural Regulation of Sexual Solicitation in Female Syrian Hamsters: Role of Oxytocin

Martinez, Luis A 20 May 2013 (has links)
In most animal species, reproductive success depends critically on precopulatory or solicitational behaviors that occur prior to mating. The specific sensory systems and behavioral strategies employed in precopulatory behaviors vary across species; in all cases, however, animals must be able to identify potential mating partners and solicit sexual interest. Female Syrian hamsters (Mesocricetus auratus) engage in multiple forms of precopulatory behaviors that are preferentially expressed to males or their odors, including vaginal scent marking and sexual odor preference. Conspecific odors relevant for precopulatory behaviors are processed by a network of forebrain areas that includes the bed nucleus of the stria terminalis (BNST) and the medial preoptic area (MPOA). The precise functional and neurochemical mechanisms whereby these areas regulate the expression of precopulatory behaviors, however, are unknown. Therefore, the aim of this dissertation is to address the following research questions: (1) Is the neuropeptide oxytocin (OT), acting within BNST or MPOA, necessary for the normal expression of odor-­guided precopulatory behaviors? (2) Is BNST or (3) MPOA required for the preferential expression of vaginal marking or investigation towards male odors?, and (4) Does OT interact with social odor processing to regulate vaginal marking? We found that blockade of OT receptors (OTRs) in MPOA and BNST decreased vaginal marking to male odors. There was no effect of OTR blockade on sexual odor preference. Selective lesions of BNST also disrupted preferential vaginal marking responses to male odors, without affecting sexual odor preference. In contrast, lesions of MPOA disrupted odor preference without affecting vaginal marking responses. Finally, central blockade of OTRs eliminated the normal pattern of increased activation of neurons to male vs. female odors in BNST, but not MPOA. Considered together, these results suggest that OT normally acts within BNST to drive preferential vaginal marking responses to male odors via selective facilitation of neural responses to these odors, and further, that there are separate and distinct neural circuits that regulate different forms of odor-guided precopulatory behaviors in females.
48

Frontal Lobe Involvement in a Task of Time-Based Prospective Memory

McFarland, Craig January 2007 (has links)
Time-based prospective memory has been found to be negatively affected by aging, possibly as a result of the declining frontal function that often accompanies aging. In the present study we investigated the role of the frontal lobes in prospective memory. Based upon their scores on a composite measure of frontal function, 32 older adults were characterized as possessing high- or low-frontal function, and were then tested on a time-based laboratory prospective memory task. Overall age effects were also assessed and each of the frontal groups was compared to a group of 32 younger adults. High-frontal functioning participants demonstrated better prospective memory than low-frontal functioning participants, and were not distinguishable from younger adults. The results of this study suggest that it is not aging per se that disrupts prospective memory performance, but it is instead the diminished frontal function seen in a subset of older adults.
49

Regulating the anterior medial prefrontal cortex : exploratory investigation of real-time fMRI training

Smith, Rachelle Marie 11 1900 (has links)
The feasibility of using real-time functional magnetic resonance imaging (fMRI) feedback regarding the level of activation in rostromedial prefrontal cortex (rMPFC) to learn improved regulation of this brain area was examined in a group of 5 young adults. Subjects received real-time feedback from the target brain region while engaging in a blocked-design task involving alternating blocks of attempted up-regulation and down-regulation of the target brain region. A transient negative emotional state was induced prior to each scanning session. Subjects completed 6 scanning sessions (a pre-training session, 4 feedback sessions and a post-training session - no feedback was provided for pre and post-training sessions). The guideline strategy provided to subjects of engaging in emotional awareness during up-regulation and bodily awareness during down-regulation was found to consistently regulate the region in the pre-training session prior to the fMRI feedback sessions. This finding is in line with the previously proposed role of the rMPFC in emotional awareness. In contrast to previous real-time fMRI findings, greater recruitment of the region was observed in the pre-training session compared to the post-training session, with a non-significant negative trend observed across feedback sessions. These results suggest that there may be limitations to which the feedback techniques successfully employed for other brain regions extend to yet unexplored brain regions.
50

Ugdymo kirtimų projektavimas ir vertinimas / Planning and estimation of forest thinning

Banys, Tomas 09 June 2005 (has links)
The purpose of this study is to explore haw thinning planning standards agree with standards of estimation. Study was carried out in Kretinga forest enterprise Grūšlaukė forestry. Study of ratio of stands medial diameter and medial high was carried out in 11 – 60 years old pure spruce. The main purpose of thinning is to increase total productivity of forest stands and to form desirable structure and closeness of stands. It is important that all kinds of forest thinning concern biodiversity, increase resistance to wind and snow damage of forest stands, improve the quality of growing timber. Forests thinning use that timber part which rots in forests and gives no profit. To reach all these purpose forests thinning must be planned. Planning standard must be definite as it possible. It is important that these standards be suit with forests thinning normative. It was estimated that both standards has different rates and they are not matched. Thinning is planning by thickness of stands, but they are estimating by the number of trees in one hectare of stands. It was estimated that the ratio of forest stands medial diameter and medial high can be used in thinning planning. In pure spruce stands thinning must planned until ratio of medial diameter and medial high reach value: 0,8 in 11 – 20 years old stands; 0,9 in 21 – 40 years old stands; 1,0 in 41 – 60 years old stands.

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