• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 132
  • 47
  • 25
  • 10
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 270
  • 69
  • 57
  • 27
  • 25
  • 23
  • 22
  • 21
  • 20
  • 17
  • 17
  • 17
  • 15
  • 15
  • 15
  • 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.
61

Promoting Pleasure in Reading Through Sustained Silent Reading: A Self-Study of Teacher Practices

McKell, Kimberly Turley 01 August 2018 (has links)
According to a survey, the majority of fourth grade students in 2005 did not choose reading as a preferred activity for entertainment (Guthrie, McRae, & Klauda, 2007). Adolescents are increasingly resistant to reading and seldom list it as a pleasurable activity. Interestingly, research shows that students who enjoy reading more do better academically (Gambrell, 2011). Accordingly, as a teacher I seek to increase students' reading for pleasure. To give space in my curriculum for students to do this and for me to support them, I used Sustained Silent Reading (SSR), a practice where students are given time to read a text of their choosing during class time. Adhering to LaBoskey's (2004) criteria for self-studies, I conducted a self-study of teacher practices. There were two rounds of field notes with critical friend commentary that allowed me to identify types of readers and types of responses. To present my findings, I developed vignettes to capture my field notes about types of readers and I identified field notes that captured general and specific responses to readers for which I provided exemplar on my findings. I also attended to trustworthiness. This study explored what I as a teacher know and learned about increasing my students' engagement with reading for pleasure during SSR time. By categorizing my students' habits and charting my responses and interventions, I was able to understand what practices to use to encourage students to read for pleasure according to their characteristics.
62

Identifying Catalysts for Sustained Innovation of Inclusion Teachers

Switzer, Laura J. 01 May 1999 (has links)
The researcher examined nine areas of support that can be of assistance to sustaining innovative methodology in four school systems in Upper East Tennessee. Five types of innovation were examined. This study looked at nine supports as well as years of involvement by the practicing educator. The research design was a comparative study with forty hypotheses used to test differences in perceived degree of assistance to commitment. Teachers were surveyed and asked to rate supports for sustained innovation. Teachers also rated actual and ideal involvement. The research questions were tested and statistically analyzed using t-test and analysis of variance. Significant differences were found between demographic groups. Teachers sustaining child-centered instruction rated seven of the nine areas of support significantly higher than peer teachers. The methodology of student assessment had five areas of support rated significantly higher, alternative scheduling had two areas of support rated significantly higher, and the thematic approach had one area. Training/conference/workshops was the only area of support that had a significant difference common to all four of these methodologies. Recommendations for further research were made to augment the study.
63

Evaluating the Efficacy of Shaping with a Percentile Schedule to Increase the Duration of Sustained Interaction Following a Bid for Joint Attention in Children with Autism

Gutbrod, Therese 11 June 2014 (has links)
This study examined the use of shaping with a percentile schedule to increase the duration of the interaction following a bid for joint attention in children with autism. Specifically, the therapist initiated a bid for joint attention and reinforced longer successive approximations in seconds of sustained interaction with the therapist and activity. A percentile schedule ranked the most recent 10 observations and reinforcement was provided if the current observation equaled the sixth ranking. Most-to-least prompting was used if the child failed to meet the calculated criterion. Shaping with a percentile schedule of reinforcement was effective at increasing the duration of sustained interaction following a bid for joint attention, for all participants from an average baseline duration of 13 s to an average intervention duration of 215 s.
64

Drive Out Fear (Unless You Can Drive It In):The role of agency and job security in process improvement

Repenning, Nelson 11 1900 (has links)
Understanding the wide range of outcomes achieved by firms trying to implement TQM and similar process improvement initiatives presents a challenge to management science and organization theory: a few firms reap sustained benefits from their programs, but most efforts fail and are abandoned. A defining feature of such techniques is the reliance on the front-line workforce to do the work of improvement, thus creating the possibility of agency problems; different incentives facing managers and workers. Specifically, successfully improving productivity can lead to lay-offs. The literature provides two opposing theories of how agency interacts with the ability of quality-oriented improvement techniques to dramaticlly increase productivity. The 'Drive Out Fear' school argues that firms must commit to job security, while the 'Drive In Fear' school emphasizes the positive role that insecurity plays in motivating change. In this study a contract theoretic model is developed to analyze the role of agency in process improvement. The main insight of the study is that there are two types of job security, internal and external, that have opposite impacts on the firm's abilty to implement improvement initiatives. The distinction is useful in explaining the results of different case studies and can reconcile the two change theories. / National Science Foundation, grant SBR-9422228, the Ford Motor Company and the Harley-Davidson Motor Company
65

Sustained acidosis and phenylephrine activate the myocardial Na+/H+ exchanger through phosphorylation of Ser770 and Ser771

Coccaro, Ersilia 06 1900 (has links)
The mammalian Na+/H+ exchanger isoform 1 (NHE1) is a ubiquitously expressed membrane protein that regulates myocardial intracellular pH. Inhibition of NHE1 prevents hypertrophy and reduces ischemia-reperfusion (I/R) injury in animal models. To understand the regulation of NHE1 in the myocardium by phosphorylation we constructed adenoviruses, which express wild type or mutant cDNA for NHE1. Additionally, wild type and mutant NHE1 had mutations Leu163Phe/Gly174Ser, which increases NHE1 resistance to EMD87580 (NHE1 inhibitor) by 100-fold. This allowed measurement of exogenous NHE1 activity while inhibiting endogenous NHE1 activity. We examined the effects of a series of mutations of phosphorylation sites in the cytosolic domain of NHE1. Sustained intracellular acidosis and phenylephrine caused an ERK-dependent activation of NHE1 activity and phosphorylation levels. We demonstrated that amino acids Ser770 and Ser771 were essential for activation of NHE1 activity in isolated rat cardiomyocytes by sustained intracellular acidosis and phenylephrine. Furthermore, mutation of Ser770 and Ser771 to Ala prevented increased NHE1 phosphorylation by sustained intracellular acidosis and phenylephrine. This was found to occur in an ERK-dependent manner. Taken together, our results demonstrate that both sustained intracellular acidosis and phenylephrine rapidly activate the NHE1 protein in isolated cardiac cells via an ERK-dependent pathway that acts on the common amino acids Ser770 and Ser771 of the C-terminal tail of NHE1.
66

Mise au point et évaluation des microparticules lipidiques solides en vue du développement galénique de préparations pour inhalation à libération prolongée/ Development and evaluation of solid lipid microparticles as sustained release system for pulmonary drug delivery

Jaspart, Séverine 26 January 2007 (has links)
Le développement de formes à libération prolongée destinées à ladministration pulmonaire est un domaine qui a, jusquà présent, été relativement peu étudié mais pour lequel il y a actuellement un intérêt croissant. Le but de notre travail est de développer une forme destinée à ladministration par inhalation qui libérerait de façon prolongée un agent bronchodilatateur. Dans le cadre de ce travail, les microparticules lipidiques solides (MLS) ont été choisies comme véhicule en vue de lobtention dune libération prolongée. Les MLS présentent en effet de nombreux avantages en termes de coûts de production, de stabilité et de biocompatibilité comparativement à dautres systèmes microparticulaires. Le salbutamol, principe actif ß2-mimétique choisi initialement pour cette étude, nétant pas suffisamment lipophile pour sincorporer de façon efficace dans les MLS, un dérivé plus lipophile du salbutamol, lacétonide de salbutamol (AS) a été synthétisé. Les caractéristiques physico-chimiques de lAS ont été déterminées, sa stabilité a été évaluée et des méthodes de dosage ont été mises au point. Des MLS vierges (non chargées en AS) ont tout dabord été produites après optimisation des paramètres de fabrication en vue dobtenir une taille adéquate pour ladministration par inhalation. Des études de tolérance au niveau pulmonaire effectuées in vivo sur des rats ont montré la biocompatibilité de ces MLS. Lactivité pharmacologique de lAS a été évaluée à la fois par des essais ex vivo de bronchodilatation sur organes isolés ainsi que par des essais daffinité (binding) envers les récepteurs ß1 et ß2-adrénergiques. Ces études nont malheureusement pas permis de conclure avec certitude quant à léventuel effet ß2-mimétique de lAS. Cependant, en raison de son caractère lipophile, lAS sera utilisé comme molécule modèle tout au long du processus de développement. LAS a donc été incorporé dans les MLS et les paramètres de production ont été étudiés et fixés par la méthodologie des plans dexpérience en vue doptimiser le pourcentage de particules possédant un diamètre géométrique convenant à ladministration par inhalation. La concentration en AS naffectant pas de façon significative la taille des MLS, celles-ci pourront être produites en utilisant la concentration en AS désirée. La caractérisation de ces MLS par microscopie électronique a montré que, lorsque la charge théorique initiale augmente, des cristaux dAS sont observés à lextérieur des MLS. Des essais de libération menés in vitro dans un premier temps puis ex vivo (en présence de fragments de poumons de porcs) ont permis de montrer une prolongation de la libération de lAS à partir des MLS comparativement à la libération à partir de mélanges physiques de MLS vierges et dAS. Ces résultats montrent la capacité des MLS possédant une taille pour administration pulmonaire, à libérer de façon prolongée la molécule qui y est incorporée. Cette libération est dautant plus prolongée que la charge en AS diminue. La présence denzymes pulmonaires na cependant pas modifié la cinétique de libération. Des poudres pour inhalation à base de MLS à 5% en AS ont été formulées en utilisant différents excipients porteurs et compétiteurs en différentes concentrations relatives. Les fractions respirables mesurées in vitro sont, dans le meilleur des cas, égales à 15%. Cependant, les MLS à 5% en AS administrées seules ont une fraction respirable proche de 25%. Leurs propriétés découlement savérant acceptables, il peut être envisagé dadministrer les MLS telles quelles en tant que poudre pour inhalation./ The sustained release of drugs for pulmonary delivery is a research field which has been so far rather unexploited but which is currently becoming increasingly attractive. The aim of this research work is to develop a pulmonary delivery system which will be able to sustain the release of a bronchodilator agent. Therefore, solid lipid microparticles (SLMs) were chosen in order to provide a sustained release to its incorporated substance. Indeed, this kind of drug carrier offers many advantages. In comparison with other microparticulate dosage forms, SLMs production costs are relatively low, they are physiologically compatible and their physical stability is well established. Salbutamol, a well-known short-acting ß2-adrenergic receptor agonist, was initially chosen for this study but this molecule proved to be not lipophilic enough to be efficiently incorporated into SLMs. Thats the reason why salbutamol acetonide (SA) was synthetized from salbutamol in order to get a more lipophilic molecule and thereby to increase the incorporation into SLMs. Then, the physico-chemical properties of SA were characterized, its stability was studied and chromatographic assays were developed. Drug free SLMs were produced using manufacturing parameters which were optimized in order to get particles with a suitable range of size for pulmonary administration. Tolerance studies were then carried out in vivo on rats to check SLMs biocompatibility in the respiratory tractus. Ex vivo tests using isolated organs were carried out in order to investigate the bronchodilating activity of SA. The obtained results were completed with a binding study to evaluate the affinity between SA on the one hand and ß1 and ß2-adrenergic receptors on the other hand. Unfortunately those studies didnt allow us to conclude about the possible ß2-mimetic activity of SA. Owing to its lipophilic character, SA will be used all along this research work as a model molecule for the development of SLMs as sustained release system for pulmonary delivery. SA was then incorporated into SLMs: the production parameters were studied using the methodology of experimental design in order to optimize the percentage of particles with a suitable diameter for pulmonary administration. It has been noticed that SA concentration does not affect significantly the particle size. So SLMs can be produced using the pre-established production parameters whatever the desired SA concentration. The characterization of the obtained SLMs-SA by scanning electron microscopy showed especially that SA crystals appear outside of the particles when the theoretical drug loading increases. Drug release studies were carried out both in vitro and ex vivo i.e. using fragments of porcine pulmonary tissues. These studies showed that SA release from SLMs is sustained in comparison with SA release from physical mixtures of drug free SLMs and SA. The obtained results tend to prove that produced SLMs are suitable carriers in order to get a sustained release of the incorporated substance. It has also been noticed that the release rate increases when the drug loading increases. Concerning the ex vivo studies, it may be concluded that the presence of pulmonary enzymes does not modify SA release profiles. Inhalation powders containing SLMs with 5% SA were finally developed using different carrier excipients and ternary agents at different relative concentrations. Respirable fractions were determined in vitro and proved to be at best equal to 15%. However, SLMs 5% SA have also been administered alone without any additional excipients. In this case, the obtained respirable fraction is close to 25%. Seeing that the flowability of SLMs 5% SA appeared to be acceptable, they could be administered just as they are as inhalation powder.
67

Die Rekonstruktion invarianter Phasenmodelle aus Daten / Reconstructing invariant phase models from data

Kralemann, Björn Christian January 2010 (has links)
Ziel dieser Arbeit ist die Überwindung einer Differenz, die zwischen der Theorie der Phase bzw. der Phasendynamik und ihrer Anwendung in der Zeitreihenanalyse besteht: Während die theoretische Phase eindeutig bestimmt und invariant unter Koordinatentransformationen bzw. gegenüber der jeweils gewählten Observable ist, führen die Standardmethoden zur Abschätzung der Phase aus gegebenen Zeitreihen zu Resultaten, die einerseits von den gewählten Observablen abhängen und so andererseits das jeweilige System keineswegs in eindeutiger und invarianter Weise beschreiben. Um diese Differenz deutlich zu machen, wird die terminologische Unterscheidung von Phase und Protophase eingeführt: Der Terminus Phase wird nur für Variablen verwendet, die dem theoretischen Konzept der Phase entsprechen und daher das jeweilige System in invarianter Weise charakterisieren, während die observablen-abhängigen Abschätzungen der Phase aus Zeitreihen als Protophasen bezeichnet werden. Der zentrale Gegenstand dieser Arbeit ist die Entwicklung einer deterministischen Transformation, die von jeder Protophase eines selbsterhaltenden Oszillators zur eindeutig bestimmten Phase führt. Dies ermöglicht dann die invariante Beschreibung gekoppelter Oszillatoren und ihrer Wechselwirkung. Die Anwendung der Transformation bzw. ihr Effekt wird sowohl an numerischen Beispielen demonstriert - insbesondere wird die Phasentransformation in einem Beispiel auf den Fall von drei gekoppelten Oszillatoren erweitert - als auch an multivariaten Messungen des EKGs, des Pulses und der Atmung, aus denen Phasenmodelle der kardiorespiratorischen Wechselwirkung rekonstruiert werden. Abschließend wird die Phasentransformation für autonome Oszillatoren auf den Fall einer nicht vernachlässigbaren Amplitudenabhängigkeit der Protophase erweitert, was beispielsweise die numerischen Bestimmung der Isochronen des chaotischen Rössler Systems ermöglicht. / The aim of this work is to bridge the gap between the theoretical description of the phase dynamics of coupled oscillators and the application of the theory to model reconstruction from time series analysis. In the theory, the phase of a self-sustained oscillator is defined in an unambiguous way, whereas the standard techniques used to estimate phases from given time series provide observabledependent results, so that generally these estimates deviate from the true phase. To stress this crucial issue, we term the observable-dependent phase-like variables as protophases. The main goal of this work is to develop a deterministic transformation from arbitrary protophases to the true, unique phase of the selfsustained oscillator. This approach allows us to obtain an invariant description of coupled oscillators and of their interaction. The application of the transformation and its efficiency are illustrated by means of numerical examples, as well as by the reconstruction of phase models of the cardiorespiratory interaction from multivariate time series of ECG, pulse and respiration. Next, the transformation from protophases to phases is extended for the case of three coupled oscillators. Finally, we go beyond the phase approximation and extend the phase transformation for autonomous oscillators to the case when the amplitude dynamics cannot be neglected. This technique for example allows us to compute numerically the isochrones of the chaotic Roessler system.
68

The Relation between Self-Report Mindfulness and Performance on Tasks of Attention

Schmertz, Stefan Kennedy 04 December 2006 (has links)
The present study examined the relation between self-report mindfulness and performance on tasks measuring abilities for three aspects of attention: sustained, selective, and attention switching. Because attention regulation has been described as a core component of mindfulness, and past research suggests that experience with mindfulness meditation is associated with improved attentional skills, the present study predicted that higher self-report mindfulness would be positively related to performance on tasks of attention. Fifty undergraduate students completed self-report mindfulness questionnaires and completed a battery of attention tasks. There was mixed support for the relation between mindfulness scores and sustained attention, such that higher mindfulness scores as measured by the MAAS and CAMS-R were negatively related to target omissions on the CPT-II, but were not related to RT variability on the CPT-II or PASAT performance. Findings are discussed in the context of the measurement of self-report mindfulness, and directions for future research are considered.
69

Creep Behaviour of Post-Installed Adhesive Anchors under Various Sustained Load Levels and Environmental Exposures

El Menoufy, Adham Mohamed 08 1900 (has links)
This thesis describes an experimental study on the long-term creep behaviour of adhesive anchors under sustained tensile loads in combination with different environmental exposures. A comprehensive background and literature review is presented, focusing on various bond stress models for adhesive anchors, factors affecting their bond behavior, and an overview of available testing standards and evaluation criteria. The experimental program comprises of 82 test specimens. The specimens consist of a cylindrical shaped concrete block of 300 mm (12 inch) in diameter and 200mm (8 inch) in depth, with 15M (No. 5) deformed steel bar post-installed to an embedment depth of six times the bar diameter or 125mm (5 inch). Three types of adhesives were used for anchor installation: Type-A a fast setting two component methyl methacrylate adhesive, Type-B a fast setting two part epoxy adhesive, and Type-C a standard set two part epoxy adhesive. The study is divided into four phases. Phase I consists of 27 static pullout tests to determine the yield strength (fy) and the maximum tensile capacity of each anchor system under three exposure conditions. Phase II and Phase III consist of 36 specimens tested under sustained load levels of 40%fy (32kN) and 60%fy (48kN)under normal laboratory conditions (room temperature) and moisture exposure, respectively. Phase IV consists of 9 specimens tested under sustained load with a load level of 40%fy (32kN) with exposure to freeze/thaw cycling. All sustained load tests lasted for a period of at least 90 days. The results of the static pullout testing showed that specimens with epoxy based adhesive exhibited stronger bond strength, forcing the anchor to fail by rupture prior to bond failure. Under sustained load testing, specimens with standard set epoxy based adhesive showed insignificant creep displacement under room conditions, however, when exposed to moisture noticeable creep displacements were recorded. Specimens with both fast setting epoxy and methyl methacrylate based adhesives showed higher creep displacements under environmental exposure (moisture, freeze/thaw) versus those kept at room temperature. Displacement data from creep testing were analysed and projected over a service life span of 50 years for room temperature exposure, and for 10 years for moisture and freeze/thaw exposures. Based on the analysis results, the service life of different anchor systems was estimated. An integrated qualification and testing protocol is proposed for the creep behavior of adhesive anchors under various environmental exposures.
70

Inter-temporal Effect of Technological Capabilities on Firm Performance: a Longitudinal Study of the U.s. Computed Tomography Industry (1972-2002)

Chopra, Ankush 07 December 2007 (has links)
In this dissertation, I investigate how capabilities drive firm performance as an industry evolves. I show that in spite of significant research on firm capabilities, we do not understand whether technological capabilities continue to drive firm performance as an industry evolves or whether they become weaker drivers of performance over time. This question is also important to managers because its answer would inform whether in a given context, firms should invest in building technological capabilities or not. I predict and find that in low complementarity contexts, as technology advances, customer demand for greater product performance becomes satiated. As a result, customers neither pay for greater product performance nor buy higher performing products pre maturely. As firms lose these two levers by which technological capabilities drive performance, they find that technological capabilities become weaker drivers of performance. I also propose that when technological capabilities become weaker drivers of performance, firm performance becomes more persistent, in the sense that past performance drives future performance. Through a rigorous quantitative analysis, complemented by an in-depth qualitative analysis of the US CT scanner industry from its inception, I find support for the theory. Using robust regression and multinomial logistic regression models, I find that as technology in an industry advances, technological capabilities become weaker drivers of firm performance. I discuss the shortcomings of this research and potential for future research. I also discuss the implications of this research on capability theory, resource based view, and on existing explanations of industry shakeout. / Dissertation

Page generated in 0.0691 seconds