Second order error correction in quantum computing

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2008.Includes bibliographical references (leaf 23).Error correction codes are necessary for the development of reliable quantum computers. Such codes can prevent the lost of information from decoherence caused by external perturbations. This thesis evaluates a five qubit code for correcting second order bit-flip errors. The code consists of encoding, decoherence, decoding, and error correction steps. This work analyzes the proposed code using geometric algebra methods and examines the state of the system after each step in the process.by Sarah Sheldon.S.B

Making Every Day Count: Boys & Girls Clubs' Role in Promoting Positive Outcomes for Teens Executive Summary

This executive summary highlights the main findings from P/PV's three-year study of the role Boys & Girls Clubs play in the lives of the youth they serve. Drawing on several sources of data -- surveys of a low-income, ethnically diverse sample of approximately 320 youth (starting when they were seventh and eighth graders and following them into the ninth and tenth grades), Club attendance records over a 30-month period, and in-depth interviews with a sample of ninth graders -- we investigated the relationship between participation and three outcome areas identified by Boys & Girls Clubs of America as central to its mission: good character and citizenship, academic success and healthy lifestyles

Making Every Day Count: Boys & Girls Clubs' Role in Promoting Positive Outcomes for Teens

The third in a series of reports from P/PV's three-year study of the role Boys & Girls Clubs play in the lives of the youth they serve, Making Every Day Count examines how Club participation is related to youth's positive and healthy development in three outcome areas identified by Boys & Girls Clubs of America as central to its mission: good character and citizenship, academic success and healthy lifestyles.The report draws on several sources of data -- surveys of a low-income, ethnically diverse sample of approximately 320 youth (starting when they were seventh and eighth graders and following them into the ninth and tenth grades), Club attendance records over a 30-month period, and in-depth interviews with a sample of ninth graders -- to investigate the relationship between participation and outcomes. The findings show that teens who had higher levels of participation in the Clubs experienced greater positive change on 15 of 31 outcomes examined, including increases in integrity (knowing right from wrong) and academic confidence, decreases in incidents of skipping school, and a lower likelihood of starting to carry a weapon or use marijuana or alcohol.Qualitative data bolster these findings, providing insights from youth and staff about the practices and strategies that support the influence of the Club, as a whole, on youth's lives. The data suggest that there is a confluence of things the Clubs are doing right to serve teens and sustain their connection to the Club as they transition from middle school to high school. Interviewed staff and the teens spoke about the overall Club environment, the safe place it provides and the role of interactions with supportive adults and peers as crucial -- and, in their view, more important than specific programming -- in helping promote teens' positive development.The findings from the evaluation offer a promising picture of the role Clubs can play in the lives of teens; they also point to valuable lessons for the larger out-of-school-time field, where there is increasing interest in the question of how to effectively engage teens -- a population that has been critically underserved in many low-income communities

Identification of small extracellular RNA fragments of Mycobacterium tuberculosis

2014 Fall.Includes bibliographical references.In 2012, the World Health Organization reported 8.6 million estimated incident cases of tuberculosis, 1 million deaths among HIV-negative people, and 0.3 million deaths from HIV-associated tuberculosis. The Stop TB Partnership has a 2015 goal of reducing the 1990 prevalence rates by half. In order to accomplish this goal, there is a large effort to develop new vaccines, diagnostics, treatment, and therapeutics. Understanding how the pathogen, Mycobacterium tuberculosis, interacts with the host is critical to the development of these goals. An emerging area of interest is how host cells respond to bacterial nucleic acids; there are several bacteria that produce nucleic acids that impact pathogenesis through recognition by host pattern recognition receptors. Previous work by Obregón-Henao et al. found that the culture filtrate (CF) of M. tuberculosis was able to induce apoptosis in monocytes, and the material was identified as small stable RNAs. Through cloning, the M. tuberculosis small RNA present in the CF was found to predominantly consist of tRNA and rRNA with lengths between 30 and 70 bases. The goal of this work was to further understand the composition of the small, stable, extracellular RNA of M. tuberculosis. The first step in further elucidating the extracellular RNA population was to develop an RNA isolation method, allowing for the reliable purification of RNA from the CF of M. tuberculosis H37Rv. The method developed previously was not optimized for RNA purification, and a more streamlined method was needed. Available commercial kits did not fit the specific needs of the project as a method was needed to isolate small RNAs from large volumes of CF. The method developed resulted primarily in small RNAs and allowed for isolation of extracellular RNA free of contaminants that could interfere with biological assays, including DNA, protein, LAM, and LPS. The kinetics of RNA release into the CF was examined, comparing the rate of RNA release to that of protein. The RNA and protein were found to have parallel release rates, which could indicate active release rather than passive release of the RNA. Once a reliable RNA isolation method was developed, the composition of the extracellular RNA was interrogated utilizing Next Generation Sequencing as a high-throughput method. A pilot study was developed to determine the optimal concentration of extracellular RNA for sequencing. The Next Generation Sequencing provided a better understanding of the components of the secreted or released RNA. Ribosomal RNA and transfer RNA fragments were found to be present in the extracellular RNA, correlating to what was found by Obergón-Henao et al. A third group of small RNAs were also identified in this study, many of which corresponded to small RNAs previously reported in the literature, however novel small RNA sequences were also identified. The possibility of bias in the sequencing technology was investigated using synthesized tRNA DNA oligonucleotides (stDNA oligos) added at specific concentrations. The quantitation bias study indicated that some bias occurs, although the cause is unknown. All of the stDNA oligos in the sample were identified, giving some confidence in the qualitative nature of this technology. However, based on the possibility of bias, it may be too generous to state that the technology is truly quantitative. Based on these studies, it is possible to say with confidence that what is identified is present, but not that things are not missed. The long-term goals of this work are to fully understand how the extracellular RNA interacts with the host at a molecular level and to understand the mechanism of RNA release. In order to accomplish these goals, it will be necessary to evaluate more M. tuberculosis extracellular RNA using Next Generation Sequencing. A time course study with Next Generation Sequencing should also be done to see if the RNA composition changes over time, as well as for comparison to intracellular small RNAs. It would also be important to develop an assay to confirm fragments found using the Next Generation Sequencer, as well as to evaluate selective release from M. tuberculosis

Blinded by magic: Electrophysiological correlates of change blindness

Magicians can often hide their method for a trick in plain sight by effecting a phenomenon known as change blindness. The purpose of this study was to find the reason for why an individual is induced with change blindness. Alpha oscillations are known to impair detection of visual stimuli, but it is unclear if this is due to increased guess rate or decreased fidelity of the mental representation. Here we estimated fidelity and guess rate as a function of pre-stimulus alpha oscillations using a change blindness task. In this study, each trial began with an array of 6 Gabor patches with a fixated dot that subjects were instructed to keep their eyes on. As the array traveled to the center of the screen, it either changed direction vertically at 90 degrees or continued horizontally. When the array switched direction, one of the Gabor patches rotated 30 degrees simultaneously. Subjects were then asked to identify which patch rotated. EEG (electroencephalography) data was simultaneously recorded with eye-tracking as subjects performed the task. Twenty-eight participants performed this task, which included six blocks of forty-eight trials. There were two different types of trials: flexion, in which the array changed direction, and control, in which the array did not change direction. Reaction time tended to be slower in flexion trials, and we found that the change in direction affected the subject’s ability to see the Gabor patch rotation. Based on the event-related potential results, which are an average of EEG signals aligned to the start of a trial, we could see that the P300 differed between correct flexion, incorrect flexion, and control trials. The P300 can be interpreted as a marker of consciousness. This difference demonstrates that the subject’s attention is automatically drawn to a larger change in stimuli