A continuous-time multi-stage noise-shaping delta-sigma modulator with analog delay

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 73-75).A new continuous-time multi-stage noise-shaping delta-sigma modulator has been designed. This modulator provides high resolution and robust stability characteristics which are the primary advantages of the conventional multi-stage noise-shaping architecture. At the same time, previous critical challenges that degraded the overall performance of multi-stage noise-shaping delta-sigma modulators are eliminated through several unique techniques. Additionally, these techniques relax the requirements of each component of the proposed delta-sigma modulator. As a result, this new delta-sigma modulator architecture can provide several advantages that are not obtainable in other modulator architectures.by Do Yeon Yoon.S.M

Toward Green Synthesis of Graphene Oxide Using Recycled Sulfuric Acid via Couette-Taylor Flow

Developing eco-friendly and cost-effective processes for the synthesis of graphene oxide (GO) is essential for its widespread industrial applications. In this work, we propose a green synthesis technique for GO production using recycled sulfuric acid and filter-processed oxidized natural graphite obtained from a Couette-Taylor flow reactor. The viscosity of reactant mixtures processed from Couette-Taylor flow was considerably lower (???200 cP at 25 ??C) than that of those from Hummers' method, which enabled the simple filtration process. The filtered sulfuric acid can be recycled and reused for the repetitive GO synthesis with negligible differences in the as-synthesized GO qualities. This removal of sulfuric acid has great potential in lowering the overall GO production cost as the amount of water required during the fabrication process, which takes a great portion of the total production cost, can be dramatically reduced after such acid filtration. The proposed eco-friendly GO fabrication process is expected to promote the commercial application of graphene materials into industry shortly

A scientometric study of the limnological societies: inferences of research collaboration and core topics based on publication networks

Scientometric analysis of limnological societies and related publications revealed complex relationships among research topics and research collaborations. We applied scientometric analysis, word networks, bibliographic coupling, and author networks analysis, to 34 777 publications related to limnology and monsoon research. We analyzed usage frequencies of limnology-related words in a Google corpus and found that usage frequencies of most limnological terms peaked during the 1980s. Social interest in the term “limnology” showed a gradually decreasing trend after the late 1990s. Monsoon research was focused in the Asian–Indian region but not in the European, African, and American regions. Word networks of limnological studies related to monsoons were mainly grouped into 3 clusters (Indian monsoons, East Asian monsoons, and monsoon assessment clusters). In the citation network of limnology journals, water quality, plankton, and invertebrate research groups generally showed strong internal citation networks. An author connection map of the limnological societies revealed strong modulators in the international societies, whereas research collaboration was rather limited to small groups within the entire network. This retrospective analysis will provide meaningful information to further develop and enhance international collaboration within limnological studies

Favorable response to doxorubicin combination chemotherapy does not yield good clinical outcome in patients with metastatic breast cancer with triple-negative phenotype

<p>Abstract</p> <p>Background</p> <p>We analyzed the responses to first line treatment and clinical outcomes of metastatic breast cancer patients treated with palliative doxorubicin/cyclophosphamide (AC) according to molecular cancer subtype.</p> <p>Methods</p> <p>A retrospective analysis was performed for 110 metastatic breast cancer patients selected on the basis of palliative AC treatment and the availability of immunohistochemical data for estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2/neu) status.</p> <p>Results</p> <p>Of the 110 patients analyzed, 71 (64.5%) were hormone receptor positive (HR+), 14 (12.7%) were HER2+, and 25 (22.7%) were triple negative (TN). There were no differences in age, stage at diagnosis, total number of cycles of palliative chemotherapy, incidence of visceral metastasis, and metastatic sites with the exception of liver among breast cancer subtypes. The overall response rates to AC were 55.9% for the HR+ subgroup, 42.9% for the HER2+ subgroup, and 56.5% for the TN subgroup. The progression-free survival (PFS) in patients with HER2+ and TN were significantly shorter than in the HR+ (median PFS, 9.1 <it>vs </it>8.1 <it>vs </it>11.5 months, respectively; p = 0.0002). The overall survival (OS) was 25.4 months in the TN subgroup and 27.3 months in HER2+ subgroup. The median OS for these two groups was significantly shorter than for patients in the HR+ subgroup (median, 38.5 months; 95% CI, 30.1-46.9 months; p < 0.0001).</p> <p>Conclusions</p> <p>The response to palliative AC chemotherapy did not differ among breast cancer subtypes. Despite chemosensitivity for palliative AC, the TN subtype has a shorter overall survival than non-TN subtypes. Innovative treatment strategies should be developed to slow the course of disease.</p

Quadruple 9-mer-based protein binding microarray with DsRed fusion protein

<p>Abstract</p> <p>Background</p> <p>The interaction between a transcription factor and DNA motif (<it>cis</it>-acting element) is an important regulatory step in gene regulation. Comprehensive genome-wide methods have been developed to characterize protein-DNA interactions. Recently, the universal protein binding microarray (PBM) was introduced to determine if a DNA motif interacts with proteins in a genome-wide manner.</p> <p>Results</p> <p>We facilitated the PBM technology using a DsRed fluorescent protein and a concatenated sequence of oligonucleotides. The PBM was designed in such a way that target probes were synthesized as quadruples of all possible 9-mer combinations, permitting unequivocal interpretation of the <it>cis</it>-acting elements. The complimentary DNA strands of the features were synthesized with a primer and DNA polymerase on microarray slides. Proteins were labeled via N-terminal fusion with DsRed fluorescent protein, which circumvents the need for a multi-step incubation. The PBM presented herein confirmed the well-known DNA binding sequences of Cbf1 and CBF1/DREB1B, and it was also applied to elucidate the unidentified <it>cis</it>-acting element of the OsNAC6 rice transcription factor.</p> <p>Conclusion</p> <p>Our method demonstrated PBM can be conveniently performed by adopting: (1) quadruple 9-mers may increase protein-DNA binding interactions in the microarray, and (2) a one-step incubation shortens the wash and hybridization steps. This technology will facilitate greater understanding of genome-wide interactions between proteins and DNA.</p

An 18-year experience of tracheoesophageal fistula and esophageal atresia

PurposeTo determine the clinical manifestations and outcomes of patients with tracheoesophageal fistula (TEF) and esophageal atresia (EA) born at a single neonatal intensive care unit.MethodsA retrospective analysis was conducted for 97 patients with confirmed TEF and EA who were admitted to the neonatal intensive care unit between 1990 and 2007.ResultsThe rate of prenatal diagnosis was 12%. The average gestational age and birth weight were 37+2 weeks and 2.5±0.7 kg, respectively. Thirty-one infants were born prematurely (32%). Type C was the most common. The mean gap between the proximal and distal esophagus was 2 cm. Esophago-esophagostomy was performed in 72 patients at a mean age of 4 days after birth; gastrostomy or duodenostomy were performed in 8 patients. Forty patients exhibited vertebral, anorectal, cardiac, tracheoesophageal, renal, limb (VACTERL) association with at least 2 combined anomalies, and cardiac anomaly was the most common. The most common post-operative complications were esophageal stricture followed by gastroesophageal reflux. Balloon dilatation was performed for 1.3 times in 26 patients at a mean age of 3 months. The mortality and morbidity rates were 24% and 67%, respectively, and the most common cause of death was sepsis. The weight of approximately 40% patients was below the 10th percentile at 2 years of age.ConclusionMortality and morbidity rates of patients with TEF and EA are high as compared to those of infants with other neonatal surgical diseases. Further efforts must be taken to reduce mortality and morbidity and improve growth retardation

A Case of Infected Left Atrial Myxoma With Concomitant Mitral Valve Endocarditis

Myxoma is the most common primary tumor in the heart. Cardiac myxomas can present in various manners including embolization and fever, sometimes simulating endocarditis. However, they are rarely infected. We report here a case of an infected left atrial myxoma that seeded a normal mitral valve and atypically presented with multiple embolic events in the lower extremities along with multiple splenic and a cerebellar infarction