3,222 research outputs found

    Seeing the Forest: Applying Latent Semantic Analysis to Smartphone Discourse

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    We apply latent semantic analysis (LSA) to understand how media discourse and cognition about smartphones evolved over time. LSA is a useful method to take advantage of large amounts of available text, discern meaning within the text, and see how meanings change over time, across the media coverage in the sector. We explain the theory of LSA, the process, and apply it to a dataset of over 83,000 media articles to create a semantic model of document and word meanings. We measure how groups of documents differ and then visualize how the discourse changes over time. We find that LSA is useful for measuring how discourse shifts across this broad set of data. In our empirical case, we find that smartphone discourse went through four distinct periods, with different dynamics of transition and stability. These characteristics suggested particular theoretical bases which LSA is also well suited to examine

    Estimating Propensity Parameters Using Google PageRank and Genetic Algorithms

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    Stochastic Boolean networks, or more generally, stochastic discrete networks, are an important class of computational models for molecular interaction networks. The stochasticity stems from the updating schedule. Standard updating schedules include the synchronous update, where all the nodes are updated at the same time, and the asynchronous update where a random node is updated at each time step. The former produces a deterministic dynamics while the latter a stochastic dynamics. A more general stochastic setting considers propensity parameters for updating each node. Stochastic Discrete Dynamical Systems (SDDS) are a modeling framework that considers two propensity parameters for updating each node and uses one when the update has a positive impact on the variable, that is, when the update causes the variable to increase its value, and uses the other when the update has a negative impact, that is, when the update causes it to decrease its value. This framework offers additional features for simulations but also adds a complexity in parameter estimation of the propensities. This paper presents a method for estimating the propensity parameters for SDDS. The method is based on adding noise to the system using the Google PageRank approach to make the system ergodic and thus guaranteeing the existence of a stationary distribution. Then with the use of a genetic algorithm, the propensity parameters are estimated. Approximation techniques that make the search algorithms efficient are also presented and Matlab/Octave code to test the algorithms are available at http://www.ms.uky.edu/~dmu228/GeneticAlg/Code.html

    On-Orbit Assembly of Flexible Space Structures with SWARM

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    On-orbit assembly is an enabling technology for many space applications. However, current methods of human assisted assembly are high in cost and risk to the crew, motivating a desire to automate the on-orbit assembly process using robotic technology. Construction of large space structures will likely involve the manipulation of flexible elements such as trusses or solar panels, and automation for assembly of flexible structures has significant challenges, particularly in control systems. This paper presents results of ground-based experiments on the assembly of a flexible space structures using the hardware developed under the Self-Assembling Wireless Autonomous Reconfigurable Modules (SWARM) program. Results are shown for a series of incremental tests that demonstrate control of a flexible structure, docking, and reconfiguration after docking. These results demonstrate the feasibility of the assembly of flexible structures using this methodology.United States. National Aeronautics and Space Administration. Small Business Innovation Program (Contract NNM07AA22C

    Heterogeneity Exhibited in Cells that Escape from Drug-Induced Senescence

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    Maintaining genomic integrity is key in the prevention of cancer. To limit the accumulation of mutations over time and stop damaged cells from continuing to proliferate and further gain subsequent mutations, intrinsic terminal cellular programs are activated. Senescence, an evolutionarily conserved stress state that traditionally has been viewed as an irreversible state of cell cycle arrest, acts as a tumour suppressive barrier. However, senescence acts as a double-edged sword, as senescent cells accumulate and contribute to age-associated diseases by altering tissue microenvironments and disrupting tissue homeostasis. Atrophied telomeres, mitotic errors, diminished DNA damage response and loss of nuclear envelope integrity all contribute to the increased rate of the formation of senescent cells during aging. In this study, I observed an age-associated accumulation of cytoplasmic DNA, in the form of micronuclei and chromatin bridges. I extended these finding to rare segmental accelerated aging diseases such as classical and non-classical Hutchinson-Gilford progeria syndrome, and Dyskeratosis Congentia. I further reveal that age-associated micronuclei and chromatin bridges undergo DNA damage and are recognized by cGAS that likely initiates an innate immune inflammatory response. My findings, along with recent reports showing chromosomal instability in senescent cells, led me to hypothesize that senescence may be reversible. To address this question, I utilized a drug-induced senescence model in BJ fibroblast and leukemia cells. Performing cloning experiments and monitoring single cells, I show that escape from a drug-induced senescent-like state occurs in a rare sub-population of cells for both transformed and normal cells. The escaped population displayed phenotypic heterogeneity, with respect to drug-response, gene expression, rate of proliferation and duration of arrest. RNA-sequencing highlighted the extensive transcriptional and metabolic reprogramming senescent cells undergo. Inhibition of lysosome function with FDA approved drug, chloroquine, specifically kills some senescent leukemia cells. By stratifying acute myeloid leukemia patients based on expression of senescent-associated gene signatures, I show that senescent gene signatures are associated with poorer overall survival. My findings provide evidence challenging the previous notion that senescence is a permanent state of cell cycle arrest and may be a mechanism which cancer cells exploit to survive therapy

    Do Not Call Me Chief Information Officer, But Chief Integration Officer. A Summary of the 2011 Detroit CIO Roundtable

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    In 2011 a roundtable meeting of Chief Information Officers (CIOs) that was organized by the Manufacturing Information systems Center at the School of Business Administration at Wayne State University discussed the emergence of public cloud computing and how this is changing the role of the CIO for medium- and large-sized organizations. The nine CIOs represented a range of manufacturing and service industries in the Greater Detroit area. This article summarizes the key themes of that roundtable, namely, the continuing change in role of the CIO as public cloud computing becomes mainstream. Key among those changes is not as much technological, because private clouds have been around now for quite some time, but rather in the broader and more challenging scope of responsibilities the CIOs now have. The role of the CIO is evolving from providing and supporting information technology and systems toward one largely based on managing the integration of externally acquired standardized hardware, software, and services while retaining quality control and remaining within budget, as well as the need to be more acquainted with the legal side of contracting. This changing set of CIO responsibilities has not made the technical skills any less important, but it has added a host of additional skills that the CIOs and those serving under them now need to master

    Variable Rates Of Hybridization Among Contact Zones Between A Pair Of Topminnow Species, Fundulus Notatus And F. Olivaceus

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    Pairs of species that exhibit broadly overlapping distributions, and multiple geographically isolated contact zones, provide opportunities to investigate the mechanisms of reproductive isolation. Such naturally replicated systems have demonstrated that hybridization rates can vary substantially among populations, raising important questions about the genetic basis of reproductive isolation. The topminnows, Fundulus notatus and F. olivaceus, are reciprocally monophyletic, and co-occur in drainages throughout much of the central and southern United States. Hybridization rates vary substantially among populations in isolated drainage systems. We employed genome-wide sampling to investigate geographic variation in hybridization, and to assess the possible importance of chromosome fusions to reproductive isolation among nine separate contact zones. The species differ by chromosomal rearrangements resulting from Robertsonian (Rb) fusions, so we hypothesized that Rb fusion chromosomes would serve as reproductive barriers, exhibiting steeper genomic clines than the rest of the genome. We observed variation in hybridization dynamics among drainages that ranged from nearly random mating to complete absence of hybridization. Contrary to predictions, our use of genomic cline analyses on mapped species-diagnostic SNP markers did not indicate consistent patterns of variable introgression across linkage groups, or an association between Rb fusions and genomic clines that would be indicative of reproductive isolation. We did observe a relationship between hybridization rates and population phylogeography, with the lowest rates of hybridization tending to be found in populations inferred to have had the longest histories of drainage sympatry. Our results, combined with previous studies of contact zones between the species, support population history as an important factor in explaining variation in hybridization rates

    A Guide to Text Analysis with Latent Semantic Analysis in R with Annotated Code: Studying Online Reviews and the Stack Exchange Community

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    In this guide, we introduce researchers in the behavioral sciences in general and MIS in particular to text analysis as done with latent semantic analysis (LSA). The guide contains hands-on annotated code samples in R that walk the reader through a typical process of acquiring relevant texts, creating a semantic space out of them, and then projecting words, phrase, or documents onto that semantic space to calculate their lexical similarities. R is an open source, popular programming language with extensive statistical libraries. We introduce LSA as a concept, discuss the process of preparing the data, and note its potential and limitations. We demonstrate this process through a sequence of annotated code examples: we start with a study of online reviews that extracts lexical insight about trust. That R code applies singular value decomposition (SVD). The guide next demonstrates a realistically large data analysis of Stack Exchange, a popular Q&A site for programmers. That R code applies an alternative sparse SVD method. All the code and data are available on github.com

    Type I Interferons Regulate Cytolytic Activity of Memory CD8+ T Cells in the Lung Airways during Respiratory Virus Challenge

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    SummaryMemory CD8+ T cells in the lung airways provide protection from secondary respiratory virus challenge by limiting early viral replication. Here, we demonstrate that although airway-resident memory CD8+ T cells were poorly cytolytic, memory CD8+ T cells recruited to the airways early during a recall response showed markedly enhanced cytolytic ability. This enhanced lytic activity did not require cognate antigen stimulation, but rather was dependent on STAT1 transcription factor signaling through the interferon-α receptor (Ifnar1), resulting in the antigen-independent expression of granzyme B protein in both murine and human virus-specific T cells. Signaling through Ifnar1 was required for the enhanced lytic activity and control of early viral replication by memory CD8+ T cells in the lung airways. These findings demonstrate that innate inflammatory signals act directly on memory T cells, enabling them to rapidly destroy infected host cells once they enter infected tissues

    Association of the Frequency of Respiratory Illness in Early Childhood with a Change in the Distribution of Blood Lymphocyte Subpopulations

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    Little is known about the distribution of lymphocyte phenotypes in young children and the association specific phenotypes may have with respiratory illnesses. The objective of this study was to describe lymphocyte distributions in children at approximately 2 years of age and to test for associations with the frequency of respiratory illness during the first 2 years of life. We hypothesized that an increased frequency of illness would be associated with those phenotypes that reflect previous antigen exposure and/or immune activation. Seventy-three children were followed during their first 2 years of life with daily symptom diaries and twice-monthly telephone calls to ascertain the incidence of respiratory illness. After the children reached 2 years of age, the phenotypes of circulating blood lymphocytes were measured by flow cytometry. Associations between illness and phenotypes were adjusted for education level of parents; hours per week in day care; hours per week exposed to environmental tobacco smoke, mould, or water damage in bedroom; and parental history of allergy and asthma. The resulting median lymphocyte count was 4.0 Ă— 109 per litre (standard deviation, 1.3) with a CD4/CD8 count of 2.28, consistent with published values. Illness rates were positively associated with the percentage of CD8+ CD38+ T cells (unadjusted p = .03, adjusted p = .014), CD8+ CD45RO+ T cells (unadjusted p = .06, adjusted p = .036), and CD4+ CD45RO+ T cells (unadjusted p = .01, adjusted p = .005). Our conclusions is that there is an association between the distribution of lymphocyte phenotypes and the incidence of respiratory illness early in life. Future research is recommended to determine the directionality of this association

    The bacterial gut microbiome of probiotic-treated very-preterm infants: changes from admission to discharge

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    Background: Preterm birth is associated with the development of acute and chronic disease, potentially, through the disruption of normal gut microbiome development. Probiotics may correct for microbial imbalances and mitigate disease risk. Here, we used amplicon sequencing to characterise the gut microbiome of probiotic-treated premature infants. We aimed to identify and understand variation in bacterial gut flora from admission to discharge and in association with clinical variables. Methods: Infants born <32 weeks gestation and <1500 g, and who received probiotic treatment, were recruited in North Queensland Australia. Meconium and faecal samples were collected at admission and discharge. All samples underwent 16S rRNA short amplicon sequencing, and subsequently, a combination of univariate and multivariate analyses. Results: 71 admission and 63 discharge samples were collected. Univariate analyses showed significant changes in the gut flora from admission to discharge. Mixed-effects modelling showed significantly lower alpha diversity in infants diagnosed with either sepsis or retinopathy of prematurity (ROP) and those fed formula. In addition, chorioamnionitis, preeclampsia, sepsis, necrotising enterocolitis and ROP were also all associated with the differential abundance of several taxa. Conclusions: The lower microbial diversity seen in infants with diagnosed disorders or formula-fed, as well as differing abundances of several taxa across multiple variables, highlights the role of the microbiome in the development of health and disease. This study supports the need for promoting healthy microbiome development in preterm neonates
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