Luminescent, quantum dot-based anti-reflective coatings for crystalline silicon photovoltaics

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 107-116).This thesis demonstrates and evaluates the potential application of luminescent quantum dot/polymer solutions on crystalline silicon photovoltaics. After spin coating the QD/polymer onto silicon photodiodes, an increase of 3% in current density was observed. This performance improvement was used to determine the impact application would have on the crystalline silicon photovoltaic supply chain. Supply chain costs were modeled to estimate the segment costs for Sharp's NUU230F3 230W module. The benefits realized by use of cells coated with the QD/polymer solution were then estimated at both the module and the cell segments. Finally, an installation cost model for the residential market was built to determine the impact an increase in efficiency had on total system costs.by Garrett Bruer.M.Eng

Time–Data Tradeoffs by Aggressive Smoothing

This paper proposes a tradeoff between sample complexity and computation time that applies to statistical estimators based on convex optimization. As the amount of data increases, we can smooth optimization problems more and more aggressively to achieve accurate estimates more quickly. This work provides theoretical and experimental evidence of this tradeoff for a class of regularized linear inverse problems

Dysregulation of synaptic pruning as a possible link between intestinal microbiota dysbiosis and neuropsychiatric disorders

The prenatal and early postnatal stages represent a critical time window for human brain development. Interestingly, this window partly overlaps with the maturation of the intestinal flora (microbiota) that play a critical role in the bidirectional communication between the central and the enteric nervous systems (microbiota-gut-brain axis). The microbial composition has important influences on general health and the development of several organ systems, such as the gastrointestinal tract, the immune system, and also the brain. Clinical studies have shown that microbiota alterations are associated with a wide range of neuropsychiatric disorders including autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, and bipolar disorder. In this review, we dissect the link between these neuropsychiatric disorders and the intestinal microbiota by focusing on their effect on synaptic pruning, a vital process in the maturation and establishing efficient functioning of the brain. We discuss in detail how synaptic pruning is dysregulated differently in the aforementioned neuropsychiatric disorders and how it can be influenced by dysbiosis and/or changes in the intestinal microbiota composition. We also review that the improvement in the intestinal microbiota composition by a change in diet, probiotics, prebiotics, or fecal microbiota transplantation may play a role in improving neuropsychiatric functioning, which can be at least partly explained via the optimization of synaptic pruning and neuronal connections. Altogether, the demonstration of the microbiota's influence on brain function via microglial-induced synaptic pruning addresses the possibility that the manipulation of microbiota-immune crosstalk represents a promising strategy for treating neuropsychiatric disorders

Thermal Conductivity, Heat Sources and Temperature Profiles of Li-ion Secondary Batteries

We measure and report the thermal conductivity of several commercial and non-commercial Li-ion secondary battery electrode materials, with and without electrolyte solvents. We also measure the Tafel potential, the ohmic resistance, reaction entropy and external temperature of a commercial pouch cell secondary Li-ion battery. Finally we combine all the experimentally obtained data in a thermal Fourier model and discuss the corresponding internal and external temperature profiles during charging and discharging. Electrochemical accumulators and power sources can be both very effective and efficient energy converters. However, as one seeks to intensify both volumetric and specific capacity the heat of these is an inevitable topic in engineering. Moreover, in order to increase performance, the electrodes are necessarily made porous, so that the active specific surface can be increased. In doing so, the thermal conductivity can be lowered by several orders of magnitude. Literature describing thermal conductivity of this property of different Li-ion electrodes is scarse, according to recent reviews e.g. [1], although it is very important. For the ex-situ thermal conductivity measurements we chose commercial electrode materials and for the temperature profile measurements and the electrochemical characterisation we chose a commercial Li-ion pouch cell battery. The electrode materials that we investigated with respect to thermal conductivity were a commercial cathode material (LiCoO 3 ) and a commercial anode material (SLP50). These materials were measured with in an already established procedure [2], both as dry pristine electrode and with a surplus of an electrolyte solvent. The commercial battery was characterised by classical charge and discharge cycling at different current rates.. These experiments were performed in a temperature regulated cabinet with a thermocouple on the battery surface and another in the ambient air. Thus all information required to model the battery's internal and external temperature profiles were collected for the modelling part. The thermal conductivity of dry and soaked electrode material was found to be 0.30 ±0.01 and 0.89±0.04 W K -1 m -1 for the anode material and 0.36±0.003 and 1.10±0.06 for the cathode material. For all materials examined it was found that adding electrolyte solvent increased the thermal conductivity by at least a factor of three. Measuring and combining the surface and the ambient temperatures of an air cooled commercial pouch cell battery at ±2°C, the electric heat sources, and the thermal conductivity of the electrode components made it possible to estimate internal and external temperature profiles at any current density. At 12C charging rate (corresponding to 5 minutes complete charging) the internal temperature differences was estimated to be in the range of 3-4 K, depending on the electrode thermal conductivity. The external temperature drop in air flowing (by forced convection) at the battery surface was estimated to nearly 70K. Thus it is clear that though it is the external temperature gradients that need the most attention with respect to engineered cooling, also internal temperatures become significant at large current rates

Growing better brains? Pregnancy and neuroscience discourses in English social and welfare policies

In recent years, English welfare and health policy has started to include pregnancy within the foundation stage of child development. The foetus is also increasingly designated as ‘at risk’ from pregnant women. In this article, we draw on an analysis of a purposive sample of English social and welfare policies and closely related advocacy documents to trace the emergence of neuroscientific claims-making in relation to the family. In this article, we show that a specific deterministic understanding of the developing brain that only has a loose relationship with current scientific evidence is an important component in these changes. We examine the ways in which pregnancy is situated in these debates. In these debates, maternal stress is identified as a risk to the foetus; however, the selective concern with women living in disadvantage undermines biological claims. The policy claim of neurological ‘critical windows’ also seems to be influenced by social concerns. Hence, these emerging concerns over the foetus’ developing brain seem to be situated within the gendered history of policing women’s pregnant bodies rather than acting on new insights from scientific discoveries. By situating these developments within the broader framework of risk consciousness, we can link these changes to wider understandings of the ‘at risk’ child and intensified surveillance over family life

Practicing a Musical Instrument in Childhood is Associated with Enhanced Verbal Ability and Nonverbal Reasoning

Background: In this study we investigated the association between instrumental music training in childhood and outcomes closely related to music training as well as those more distantly related. Methodology/Principal Findings: Children who received at least three years (M = 4.6 years) of instrumental music training outperformed their control counterparts on two outcomes closely related to music (auditory discrimination abilities and fine motor skills) and on two outcomes distantly related to music (vocabulary and nonverbal reasoning skills). Duration of training also predicted these outcomes. Contrary to previous research, instrumental music training was not associated with heightened spatial skills, phonemic awareness, or mathematical abilities. Conclusions/Significance: While these results are correlational only, the strong predictive effect of training duration suggests that instrumental music training may enhance auditory discrimination, fine motor skills, vocabulary, and nonverba

Nutrition education: a questionnaire for assessment and teaching

It is generally recognized that there is a need for improved teaching of nutrition in medical schools and for increased education of the general population. A questionnaire, derived in part from a study of physician knowledge, was administered to first year medical students in order to assess their knowledge of various aspects of nutrition and metabolism, and as a teaching tool to transmit information about the subject. The performance of first year students was consistent with a generally educated population but there were surprising deficits in some fundamental areas of nutrition. Results of the questionnaire are informative about student knowledge, and immediate reinforcement from a questionnaire may provide a useful teaching tool. In addition, some of the subject matter can serve as a springboard for discussion of critical issues in nutrition such as obesity and markers for cardiovascular disease. A major barrier to improved teaching of nutrition is the lack of agreement on some of these critical issues and there are apparent inconsistencies in recommendations of government and health agencies. It seems reasonable that improved teaching should address the lack of knowledge of nutrition, rather than knowledge of official guidelines. Student awareness of factual information should be the primary goal

How to achieve synergy between medical education and cognitive neuroscience? An exercise on prior knowledge in understanding

A major challenge in contemporary research is how to connect medical education and cognitive neuroscience and achieve synergy between these domains. Based on this starting point we discuss how this may result in a common language about learning, more educationally focused scientific inquiry, and multidisciplinary research projects. As the topic of prior knowledge in understanding plays a strategic role in both medical education and cognitive neuroscience it is used as a central element in our discussion. A critical condition for the acquisition of new knowledge is the existence of prior knowledge, which can be built in a mental model or schema. Formation of schemas is a central event in student-centered active learning, by which mental models are constructed and reconstructed. These theoretical considerations from cognitive psychology foster scientific discussions that may lead to salient issues and questions for research with cognitive neuroscience. Cognitive neuroscience attempts to understand how knowledge, insight and experience are established in the brain and to clarify their neural correlates. Recently, evidence has been obtained that new information processed by the hippocampus can be consolidated into a stable, neocortical network more rapidly if this new information fits readily into a schema. Opportunities for medical education and medical education research can be created in a fruitful dialogue within an educational multidisciplinary platform. In this synergetic setting many questions can be raised by educational scholars interested in evidence-based education that may be highly relevant for integrative research and the further development of medical education

Neuroscience and education: prime time to build the bridge

As neuroscience gains social traction and entices media attention, the notion that education has much to benefit from brain research becomes increasingly popular. However, it has been argued that the fundamental bridge toward education is cognitive psychology, not neuroscience. We discuss four specific cases in which neuroscience synergizes with other disciplines to serve education, ranging from very general physiological aspects of human learning such as nutrition, exercise and sleep, to brain architectures that shape the way we acquire language and reading, and neuroscience tools that increasingly allow the early detection of cognitive deficits, especially in preverbal infants. Neuroscience methods, tools and theoretical frameworks have broadened our understanding of the mind in a way that is highly relevant to educational practice. Although the bridge’s cement is still fresh, we argue why it is prime time to march over it