<div><div><div><p>The brain dynamically alters its production of flexible behavior: cognitive flexibility increases when demand is high. In task switching experiments, past exposure to a high demand for flexibility in conjunction with specific temporal contexts leads to learned switch readiness such that future exposures to those contexts will cue flexibility. According to a recent proposal (Dreisbach & Fröber, 2019), learned switch readiness following switch demands is supported by a concurrent activation (CA) cognitive mechanism whereby both sets of task rules are kept available in working memory despite only using one at a time. This can be differentiated from a competing candidate mechanism, working memory updating (WMU) thresholds which determine the ease of replacing one task’s rules with another. The WMU mechanism is expected to cause a global increase in flexibility while CA is conceptualized as limited to task-specific associations. To test whether learned switch readiness represents a global or limited change in the cognitive system, I conducted two experiments that both involved learning switch readiness in one context and generalizing it in another. In Experiment 1, I replicated and extended findings that switch probability manipulations can modulate voluntary switch rates (VSR), indicating one type of generalizability. However, in Experiment 2, I found that flexibility learned through switch probability manipulations did not transfer to new tasks when the task rules were changed but contextual cues remained the same, demonstrating a limit: learned switch readiness does not generalize across tasks. These findings together suggest that CA is likely the mechanism behind learned switch readiness.</p></div></div></div>

<p>  </p> <p>The world has experienced an unprecedented change in the systems responsible for food production, distribution, and commercialization with concurrent changes in diets. In developed and developing countries, the shift in consumption patterns has moved towards a Western diet pattern which has been linked to negative health outcomes including obesity, diabetes and associated non-communicable diseases. Traditional African diets have previously been associated with protective effects against the development of the above-mentioned conditions. Yet, the underlying reasons for this is not clear. One dietary factor that may contribute to its protective effect is the principal available carbohydrate, starch, which in traditional African staples is considered to contain slowly digestible carbohydrates (SDCs) and some amount of resistant starch (RS). We reported that traditional African staple starchy foods (sorghum and millet) had markedly slower gastric emptying than introduced modern starchy foods (rice, pasta and potatoes). This response was attributed to activation of enteroendocrine cells of the small intestine (L-cells) with potential to trigger physiological, hormonal, and neurological processes that affect digestion time and perception of hunger; effect known as the ileal brake. Moreover, at least in mice models, consumption of SDCs has shown to have beneficial effects on the rate and type of fuel (e.g. carbohydrate vs fat) used for metabolic processes.</p> <p>The first thesis study compared the effect of diets (cohorts in the USA and Kenya) on gastric half-emptying time and metabolic fuel utilization in healthy adults. Our findings showed that gastric emptying time was not different between cohorts and that diet did not influence gastric emptying time; however, calculated respiratory exchange ratio (RER) (which is a measure of metabolic fuel utilization at the cellular level, e.g. carbohydrate vs fat) and metabolic flexibility (which is the ability to switch between metabolic fuel sources upon demand or need) was higher for the Kenyan cohort. Multivariant models were developed and corrected for multicollinearity of some diet variables. Carbohydrate and protein in multivariate model 1; total fiber, added sugars and starch in multivariate model 2; and diet quality (measured as the Healthy Eating Index based on 2015-2020 dietary guidelines, or HEI-2015) in multivariate model 3, were significantly and independently correlated with RER and metabolic flexibility.   </p> <p>The second study assessed if slow gastric emptying and improve metabolic fuel utilization could be induced through SDC supplementation. The objective of this study was to determine if continual consumption of SDC for 21 days delayed the rate of gastric emptying, moderated postprandial glycemic response, decreased hunger, and/or improved metabolic fuel utilization in subjects with low diet quality (HEI-2015<65). Our results indicated that supplementation with SDC did not slow gastric emptying time or acute measures of metabolic fuel utilization; however, continuous consumption of SDC had a modest but significant effect on improving metabolic flexibility and decreasing hunger scores. </p> <p>The last two chapters of this thesis focused on the use of a low-cost, high-pressure, high temperature extruder suitable for processing in Africa of whole grain pearl millet (<em>Pennisetum glaucum</em>). In Africa, emerging, entrepreneurial companies are increasingly gaining share of local markets by manufacturing and distributing high-quality locally sourced processed foods made with indigenous grains. Whole pearl millet is particularly susceptible to development of rancidity. The objective of our third study was to assess the use of the extruder on the stability and sensory attributes of whole grain pearl millet extruded flours to be used for instant thin and thick porridges. Findings showed that extrusion fully gelatinized the starch in pearl millet and prevented hydrolytic rancidity in the instant flour products. However, extrusion cooking did not stop oxidative rancidity. We concluded that while extrusion cooking is a versatile technology for whole grain processing, refinement of extrusion conditions used in the experiment and the evaluation of other unit operations (e.g. steeping, germination) in combination with extrusion cooking may improve the sensory properties of final products.</p> <p>Finally, extrusion cooking has been showed to promote the formation of beneficial amylose-lipid complexes (ALCs). The objective of the last study was to evaluate the formation of ALCs in whole grain pearl millet extruded flours, characterize their composition, and assess their ability to slowly digest <em>in vitro</em>. Extrusion promoted the formation ALCs and these flours exhibited a slow enzymatic digestion <em>in vitro</em>. The findings from this thesis provide insights into the role of diets and metabolic fuel utilization, and improvement of processed pearl millet foods in Africa.</p>

Effects of a custom bite-aligning mouthguard on performance in college football players. J Strength Cond Res 30(5): 1409-1415, 2016 - Besides injury prevention, mouthguards can also be employed to improve physical performance. The effects of personalization of mouthguards have rarely been investigated. This 3-armed, randomized, controlled crossover trial investigated the difference of wearing (a) personalized or custom-made (CM, e.g., bite-aligned), (b) standard (BB, boil and bite), and (c) no (CON) mouthguards on general fitness parameters in experienced collegiate football players. A group of 10 upperclassmen (age, 19-22 years; mean ± SD: age 20.7 ± 0.8 years; body mass 83 ± 7.4 kg; height 179.1 ± 5.2 cm; body mass index 25.9 ± 2.2 kg·cm -2), National Collegiate Athletic Association Division II football players with at least 2 years of playing experience, were randomly assigned to the 3 mouthguard conditions: a randomized, within-subjects repeated-measures design was applied. All participants were randomly tested on strength and endurance performance Vo 2 max testing, with Bruce treadmill protocol including (a) time to fatigue, (b) blood lactate concentration in millimoles per liter at stage 2 and (c) at peak fatigue, (d) flexibility, (e) reaction time, (f) squat vertical jump, (g) countermovement vertical jump, and (h) 1 repetition maximum bench press. Repeated-measures analysis of variance showed no significant differences between the 3 conditions for each outcome variable (0.23 < p < 0.94; 0.007 < < 0.15). These data indicate that CM mouthguards did not superiorly affect general fitness parameters compared with BB and CON. In turn, protective BB or CM mouthpieces did not appear to impair general fitness performance vs. CON. The recommendation of a custom bite-aligning mouthguards for performance enhancement in young Division II football players is questioned. Further studies with larger sample sizes, gender comparison, and (sport) discipline-specific performance testing are needed.

Despite the abundance of research dealing with the impact of supply chain management on today's organisations, such research tended to emphasise discreet relationships. A cross-sectional sample of Portuguese organisations is used to test several hypotheses pertaining to organisational resources, competencies, different levels of supply chain integration and organisational performance. Based on the findings, the impact of information technology infrastructure flexibility exhibited mixed results on the constructs studied. Executive information technology competencies tended to positively influence the different types of supply chain integration. Internal integration was found to have a direct influence on organisational performance. Such internal integration is being encouraged by external entities including customers and suppliers. In this context, more integration might lead to more effective organisational performance. Therefore, it is concluded that organisations should integrate their resources, processes and in the process encourage effective utilisation of information.

Extensive analysis of the physical and chemical effects controlling the operation of combustion modes driven by auto-ignition is presented in this thesis. Specifically, the study integrates knowledge attained by analyzing the effects of fuel molecular structure on auto-ignition, quantity or quality of charge dilution, and in-cylinder temperature and pressure on burning characteristics in single and multiple injection strategies employed in compression ignition (CI), partially premixed combustion (PPC) and homogenous charge compression ignition (HCCI) engines. In the first section of the thesis, a multiple injection strategy aimed to produce heat at a constant pressure, commonly known as isobaric combustion, has been studied. Then, to eliminate the complexity of spray-to-spray interactions observed with isobaric combustion, the second section of the thesis is focused on compression ignition (CI) through single injection. In the final section, the presentation will move towards moderate conditions with high dilution, in which combustion becomes dominated by chemical kinetics. At these conditions, there is emerging evidence that certain fuels exhibit unusual heat release characteristics where fuel releases heat in three distinctive stages. Overall, the thesis discusses factors controlling the auto-ignition for CI, PPC and HCCI engines that can provide valuable insights to improve their operation. Isobaric combustion in CI engine involves large interactions between physical and chemical effects. Injection of spray jets into oxygen-deprived regions catalyzes the mechanism for soot production – urging to employ either multiple injectors, low reactivity fuel or an additional expansion stage. Fuels – regardless of their auto-ignition tendency – share the same combustion characteristics in the high load CI, where auto-ignition is controlled by only the injector’s physical specifications. Such observation is a showcase of the fuel flexible engines that has the potential of using sustainable fuels – without being restrained by the auto-ignition properties of the fuel. The thesis provides evidence from experiment and simulation that three-stage auto-ignition is indeed a phenomenon driven by chemical kinetics. Three-stage auto-ignition opens the perspective to overcome the limitation of the high-pressure rise rates associated with HCCI engine.

PTSD is a mental health condition that affects many people over the course of their life (National Comorbidity Survey, 2005), including veterans (Litz & Schlenger, 2009). However, many do not experience clinical levels of distress and some experience posttraumatic growth (PTG) resulting from such an event (Tedeschi, Park, & Calhoun, 1998). The Psychological Flexibility Model, of which Acceptance and Commitment Therapy (ACT; Hayes, Strosahl, & Wilson, 1999) is based, may help explain these phenomena. The purpose of this study was to examine these relationships utilizing a measure simultaneously assessing psychological flexibility and inflexibility. It was hypothesized that psychologically inflexible behaviors would predict PTSD symptom severity, while flexible behaviors would predict PTG. Furthermore, each of psychological inflexibility and flexibility would account for unique variance in PTSD symptom severity and PTG, respectively. Finally, the domains of ACT were examined to assess the strength each component has in the maintenance of these experiences. Results indicated that both psychological inflexibility and flexibility predicted PTSD symptoms and PTG, respectively, and each predicted unique variance in these experiences. Of the individual components, cognitive fusion, experiential avoidance, inaction, and lack of contact with the present moment all contributed to PTSD symptom severity, while values clarity, lack of contact with the present moment, and present moment awareness contributed to PTG. These results suggest the psychological flexibility model overall is consistent with the experience of PTSD symptoms and the posttraumatic growth. Though further experimental methods are needed, the application of psychological flexibility through ACT could enhance PTSD treatments.

Les mécanismes neuropsychologiques sous-jacents à l’expression symptomatique du trouble obsessionnel compulsif (TOC) sont encore mal connus. Nombreuses sont les études qui mettent en évidence des déficits exécutifs mais la diversité des méthodologies et la mixité des sous-types cliniques empêchent de dégager des constantes en terme de profil neurocognitif. Les études neuropsychologiques accordent toutefois une importance à l’inhibition et à flexibilité cognitive qui pourraient participer au caractère inflexible et répétitif des pensées et des actes communs à toutes les formes du TOC. L’objectif de cette thèse est l’étude des mécanismes d’inhibition et de la flexibilité chez des patients présentant un TOC. Deux études ont été réalisées. L’étude 1 est une étude de faisabilité d’un protocole de tests neuropsychologiques où 9 patients sont comparés à 9 sujets contrôles. L’étude a fait l’objet d’une bonne faisabilité. L’étude 2 compare 14 patients présentant un TOC à 16 patients présentant des troubles phobiques avec des tests informatisés d’inhibition, de flexibilité en plus des tests de l’étude 1. Les objectifs sont : vérifier l’hypothèse d’un déficit d’inhibition chez des patients TOC, étudier les relations entre la sévérité, l’ancienneté des troubles TOC et les résultats aux tests d’inhibition et de flexibilité. Les limites méthodologiques, entre autre, l’absence d’un groupe contrôle réduisent l’interprétation comparant les deux groupes cliniques ainsi que les résultats au sein du groupe de patients TOC. Les patients se sont différenciés sur deux épreuves de rapidité d’exécution en flexibilité mentale et d’attention. Au sein du groupe des patients présentant un TOC, les données ont montré une relation entre la sévérité des symptômes TOC et des perturbations aux tests d’inhibition. Ces observations sont discutées en lien avec le concept « impulsivité et TOC » / The nature of neuropsychological mechanisms underlying clinical picture of obsessive-compulsive disorders (OCD) has not, as yet, been clearly determined. Number of studies has emphasized the role of cognitive deficits, but diversity of methodology and overlapping of clinical sub-groups, did not allow establishing specific neuro-cognitive profile. Neuropsychological studies recognize, however, the place of inhibition and alteration of cognitive flexibility that could be at origins of inflexible and repetitive nature of thoughts and actions, typical of all obsessive-compulsive disorders. The aim of this thesis was to explore the mechanisms of inhibition and cognitive flexibility in patients with OCD. Two studies were carried out. In the first, pilot study, we wanted to verify the feasibility of neuropsychological tests comparing 9 OCD patients with 9 controls. The study demonstrated a good feasibility. In the second, 14 OCD patients were compared to 16 phobics, using computerized tests of inhibition and flexibility, in addition to a battery used in the first study. The objectives were to verify hypothesis of inhibition deficit in patients with OCD, to examine relationship between severity and length of OCD and the results on neuropsychological tests of inhibition and flexibility. Methodological limits with, amongst other, the absence of control group, diminish predictive value of the comparison of two clinical groups as well as between patients with OCD. However, we found differences between patients in two tests, the one of rapidity of execution in mental flexibility and the other of attention. In the group of patients with OCD, data indicated relationship between severity of symptoms of OCD and their results on tests of inhibition. These data are further discussed in terms of relationship between “impulsivity and OCD”

The New Jersey 2011 Adequate Yearly Progress report revealed that 53% (n = 75) of state schools that failed to meet standards were put on a 'priority school' list. The 2015 priority school list consisted of 66 schools. In response, New Jersey created Regional Achievement Centers to provide collaborative professional development (PD) for effective instruction in the lowest performing schools. The purpose of this transcendental phenomenological study was to explore the lived experiences of priority schoolteachers regarding experiences with past PD initiatives and PD under the current Elementary and Secondary Education Act flexibility waiver focusing on collaborative approaches that include job-embedded coaching and teacher networks. The research questions were germane to attempts to address failing schools through PD. The conceptual framework guiding the study was Fullan's educational change theory in which teachers learn by collaborating with other teachers and coaches. Through snowball sampling, 8 priority schoolteachers participated in semistructured in-depth interviews using an online conferencing tool. Data were analyzed by Moustakas' modified version of van Kaam's method. Participants did not perceive that past PD attempts addressed the needs of failing schools. Key findings regarding job-embedded coaching and teacher networks were that support given by coaches strengthened the participants' instructional practice, and teacher networks enabled the participants to collaboratively learn from each other. Positive social change may occur as district and school officials include teachers in PD planning. Adapting PD in this manner may improve implementation of PD initiatives for classroom instruction to increase student achievement.

Dans un environnement compétitif et incertain, l'industrie automobile est confrontée à de nouveaux défis pour répondre aux exigences des clients, qui sont en constante évolution. La personnalisation de masse a augmenté considérablement la diversité des produits et par conséquent, a mis à l’épreuve la capacité des systèmes de production existants à faire face à cette nouvelle conjoncture. La convertibilité traduit la capacité du système de production à produire une diversité de produits à moindre coût. Cette thèse analyse la définition et les dimensions de la convertibilité et examine les inducteurs de la convertibilité des systèmes de production et plus particulièrement celle des lignes d'assemblage automobile. En se basant sur les pratiques industrielles, un nouveau concept, baptisé AutoConvert, autour de la convertibilité du système d’assemblage automobile est explicité. Celui-ci met en exergue l'impact de l’introduction d’une nouvelle variante du produit sur les trois éléments principaux qui composent un système d’assemblage, à savoir les produits, les processus et les ressources. Ensuite, trois indicateurs technologiques sont construits pour quantifier la convertibilité du système d’assemblage et fournir, à la fois aux concepteurs des produits et des lignes d’assemblage, un outil d'aide à la décision pour appuyer leurs orientations et leurs choix. Aussi, une étude de coûts est également menée afin de compléter et consolider les indicateurs technologiques. La pertinence de l'approche est expérimentée sur des cas réels de l'industrie automobile. / : In a highly competitive and uncertain environment, the automotive industry is facing new challenges to meet customer requirements that are constantly changing. Mass customization caused that product variety increased drastically and consequently, tested the capacity of the existing production systems to cope with this new situation. Convertibility is the ability of the assembly system to cope with product variety with minimum cost. This thesis analyzes the definition and dimensions of convertibility and investigates the change drivers that make convertibility important for the case of automotive assembly lines.Based on industrial practices, a new concept is developed, named AutoConvert, regarding the automotive assembly line convertibility. It analyzes the impact of the introduction of a new variant on the three main elements which compose an assembly system, namely Products, Processes and Resources. Then, three technological indicators’ are built to quantify assembly line convertibility and provide both assembly line and product designers’ with efficient decision-making support tools to support their orientations and choices. A cost study is also conducted in order to complete and consolidate the technological indicators. The relevance of the approach is experimented in real cases from the automotive industry.

abstract: In nature, it is commonly observed that animals and birds perform movement-based thermoregulation activities to regulate their body temperatures. For example, flapping of elephant ears or plumage fluffing in birds. Taking inspiration from nature and to explore the possibilities of such heat transfer enhancements, augmentation of heat transfer rates induced by the vibration of solid and well as novel flexible pinned heatsinks were studied in this research project. Enhancement of natural convection has always been very important in improving the performance of the cooling mechanisms. In this research, flexible heatsinks were developed and they were characterized based on natural convection cooling with moderately vibrating conditions. The vibration of heated surfaces such as motor surfaces, condenser surfaces, robotic arms and exoskeletons led to the motivation of the development of heat sinks having flexible fins with an improved heat transfer capacity. The performance of an inflexible, solid copper pin fin heat sink was considered as the baseline, current industry standard for the thermal performance. It is expected to obtain maximum convective heat transfer at the resonance frequency of the flexible pin fins. Current experimental results with fixed input frequency and varying amplitudes indicate that the vibration provides a moderate improvement in convective heat transfer, however, the flexibility of fins had negligible effects. / Dissertation/Thesis / Masters Thesis Mechanical Engineering 2019