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Search Results: 1 - 10 of 22801 matches for " Elizabeth X. Kwan "
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Natural Polymorphism in BUL2 Links Cellular Amino Acid Availability with Chronological Aging and Telomere Maintenance in Yeast
Elizabeth X. Kwan,Eric Foss,Leonid Kruglyak,Antonio Bedalov
PLOS Genetics , 2011, DOI: 10.1371/journal.pgen.1002250
Abstract: Aging and longevity are considered to be highly complex genetic traits. In order to gain insight into aging as a polygenic trait, we employed an outbred Saccharomyces cerevisiae model, generated by crossing a vineyard strain RM11 and a laboratory strain S288c, to identify quantitative trait loci that control chronological lifespan. Among the major loci that regulate chronological lifespan in this cross, one genetic linkage was found to be congruent with a previously mapped locus that controls telomere length variation. We found that a single nucleotide polymorphism in BUL2, encoding a component of an ubiquitin ligase complex involved in trafficking of amino acid permeases, controls chronological lifespan and telomere length as well as amino acid uptake. Cellular amino acid availability changes conferred by the BUL2 polymorphism alter telomere length by modulating activity of a transcription factor Gln3. Among the GLN3 transcriptional targets relevant to this phenotype, we identified Wtm1, whose upregulation promotes nuclear retention of ribonucleotide reductase (RNR) components and inhibits the assembly of the RNR enzyme complex during S-phase. Inhibition of RNR is one of the mechanisms by which Gln3 modulates telomere length. Identification of a polymorphism in BUL2 in this outbred yeast population revealed a link among cellular amino acid availability, chronological lifespan, and telomere length control.
A Natural Polymorphism in rDNA Replication Origins Links Origin Activation with Calorie Restriction and Lifespan
Elizabeth X. Kwan,Eric J. Foss,Scott Tsuchiyama,Gina M. Alvino,Leonid Kruglyak,Matt Kaeberlein,M. K. Raghuraman,Bonita J. Brewer,Brian K. Kennedy,Antonio Bedalov
PLOS Genetics , 2013, DOI: 10.1371/journal.pgen.1003329
Abstract: Aging and longevity are complex traits influenced by genetic and environmental factors. To identify quantitative trait loci (QTLs) that control replicative lifespan, we employed an outbred Saccharomyces cerevisiae model, generated by crossing a vineyard and a laboratory strain. The predominant QTL mapped to the rDNA, with the vineyard rDNA conferring a lifespan increase of 41%. The lifespan extension was independent of Sir2 and Fob1, but depended on a polymorphism in the rDNA origin of replication from the vineyard strain that reduced origin activation relative to the laboratory origin. Strains carrying vineyard rDNA origins have increased capacity for replication initiation at weak plasmid and genomic origins, suggesting that inability to complete genome replication presents a major impediment to replicative lifespan. Calorie restriction, a conserved mediator of lifespan extension that is also independent of Sir2 and Fob1, reduces rDNA origin firing in both laboratory and vineyard rDNA. Our results are consistent with the possibility that calorie restriction, similarly to the vineyard rDNA polymorphism, modulates replicative lifespan through control of rDNA origin activation, which in turn affects genome replication dynamics.
Tratamento de suporte e quela??o de ferro em pacientes com síndromes mielodisplásicas
Souto, Elizabeth X.;
Revista Brasileira de Hematologia e Hemoterapia , 2006, DOI: 10.1590/S1516-84842006000300011
Abstract: myelodysplastic syndromes (mdss) are a heterogeneous group of hematological disorders which are more common in the elderly and related to chronic anemia dependent on blood transfusions. consequently, many of these patients develop iron overload which may lead to severe injury to tissues. transfusions and chelation therapy, when indicated, are important for survival and to maintain the quality of life. chelation therapy is indicated especially for mds subtypes with a better prognosis and a sufficiently long survival to develop clinically relevant iron overload. chelation therapy presents with some limitations in particular the long time required for deferoxamine infusion and the difficulties of patients to comply with treatment and to acquire an infusion pump. the clinical use of deferiprone, an oral chelator, is not indicated for mds patients because of the risk of neutropenia and agranulocytosis. deferasirox is a new oral chelator currently under clinical development that will probably be, in the future, an adequate option for mds patients with iron overload. additional studies in mds patients are necessary to establish better diagnostic and chelation therapy criteria.
A Complete Image Compression Scheme Based on Overlapped Block Transform with Post-Processing
Kwan C,Li B,Xu R,Li X
EURASIP Journal on Advances in Signal Processing , 2006,
Abstract: A complete system was built for high-performance image compression based on overlapped block transform. Extensive simulations and comparative studies were carried out for still image compression including benchmark images (Lena and Barbara), synthetic aperture radar (SAR) images, and color images. We have achieved consistently better results than three commercial products in the market (a Summus wavelet codec, a baseline JPEG codec, and a JPEG-2000 codec) for most images that we used in this study. Included in the system are two post-processing techniques based on morphological and median filters for enhancing the perceptual quality of the reconstructed images. The proposed system also supports the enhancement of a small region of interest within an image, which is of interest in various applications such as target recognition and medical diagnosis
Inference making while reading narrative and expository texts: an ERP study
Baretta, Luciane;Tomitch, Lêda Maria Braga;MacNair, Nicolas;Lim, Vanessa Kwan;Waldie, Karen Elizabeth;
Psychology & Neuroscience , 2009, DOI: 10.3922/j.psns.2009.2.005
Abstract: much of the recent research on discourse comprehension has centered on the readers' ability to construct coherent mental representations of texts. in order to form a unified representation of a given text, a reader must be able to join the information presented in the text with his/her background knowledge to construe the meaning that may not be explicitly stated, through the generation of inferences. in this study, the process of inference making by native speakers of english while reading two different types of text was investigated using electroencephalography (eeg). subjects read narrative and expository paragraphs, and judged the plausibility of the final sentence of each four-sentence long paragraph by reference to the previous information. the analysis of data focused on the n400 component and on accuracy of behavioral responses. n400 amplitudes revealed that exposition was more demanding than narration in terms of semantic processing, whereas the behavioral data showed that subjects were more prone to generate inferences when reading exposition. overall, this study suggests that these two types of text are processed differently by the brain, as revealed by the changes in the n400 component across the last sentences of the paragraphs.
INFERENCE MAKING WHILE READING NARRATIVE AND EXPOSITORY TEXTS: AN ERP STUDY
ciane Baretta, Le?da Maria Braga Tomitch, Nicolas MacNair, Vanessa Kwan Lim, Karen Elizabeth Waldie
Psychology & Neuroscience , 2009,
Abstract: Much of the recent research on discourse comprehension has centered on the readers’ ability to construct coherent mental representations of texts. In order to form a unified representation of a given text, a reader must be able to join the information presented in the text with one’s background knowledge to construe the meaning that may not be explicitly stated, through the generation of inferences. In this study, the process of inference making by native speakers of English while reading two different types of text was investigated using electroencephalography (EEG). Subjects read narrative and expository paragraphs, and judged the plausibility of the final sentence of each four- sentence long paragraph by reference to the previous information. The analysis of data focused on the N400 component and on accuracy of behavioral responses. N400 amplitudes revealed that exposition was more demanding than narration in terms of semantic processing, whereas the behavioral data showed that subjects were more prone to generate inferences when reading exposition. Overall, this study suggests that these two types of text are processed differently by the brain, as revealed by the changes in the N400 component across the last sentences of the paragraphs.
Ultra Fast Computing Using Photonic Crystal Based Logic Gates
X. Susan Christina,A. P. Kapilan,P. Elizabeth Caroline
International Journal of Computer Science and Information Security , 2010,
Abstract: A Novel design of all-optical fundamental NAND and XNOR logic gates based on two dimensional photonic crystals hasbeen presentedin this paper. In a photonic crystal self collimated beams are partially transmitted and partially reflected with a phase lag at line defect in Γ-X direction. By employing a appropriate phase shifter, the reflected and transmitted inputbeams areinterferedconstructivelyor destructively to obtain therequired logic outputs.The operation of the logic gates is simulated using two dimensional Finite Difference Time Domain (FDTD) method.
Intensive Diabetes Treatment and Cardiovascular Disease in Patients with Type 1 Diabetes
Janice Kwan
University of Toronto Medical Journal , 2006, DOI: 10.5015/utmj.v83i2.311
Abstract:
From Cherry Picking to Convergence – Migrating E-Learning Delivery to an LMS (Learning Management System) – the COLeLIO Experience
Angela Kwan
International Journal of Advanced Corporate Learning (iJAC) , 2012, DOI: 10.3991/ijac.v5i3.2174
Abstract: The Commonwealth of Learning e-learning for International Organizations (COLeLIO) (www.col.org/colelio) Initiative engages appropriate technology to custom design and deliver just-in-time (JIT) workplace e-learning for adult learners based in field offices and headquarters of international organizations spread all over the world. To ensure reliable and easy access to learning, COLeLIO chooses appropriate technologies to underpin course design, development and delivery taking into consideration bandwidth and access issues. Responding to constantly changing learning environments and learners' needs, eLIO learning materials have evolved from print to digital over the last decade. In recent years, eLIO saw the need to streamline the delivery operation for their 1,000 learners annually, involving 40 tutors and teams of course administrators. Recognizing that the conduits supporting online learning have mushroomed in recent years and that more affordable and robust open source learning management platforms are available to support and sustain online learning for transparency, accountability and quality results, COLeLIO spent 12 months searching for and adapting a technology solution to create a one-stop access to resources, support, discussions, and records for learners, tutors and administrators. This paper captures the story of change management by eLIO and shares some key lessons learned.
Sarcopenia, a Neurogenic Syndrome?
Ping Kwan
Journal of Aging Research , 2013, DOI: 10.1155/2013/791679
Abstract:
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