44 research outputs found

    The effect of field-aligned currents and centrifugal forces on ionospheric outflow at Saturn

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    Ionospheric outflow is driven by an ambipolar electric field induced due to the separation of electrons and ions in a gravitational field when equilibrium along a magnetic field line is lost. A model of ionospheric outflow at Saturn was developed using transport equations to estimate the number of charged particles that flow from the auroral regions into the magnetosphere. The model evaluates the outflow from 1,400 km in altitude above the 1 bar level, to 3 RS along the field line. The main ion constituents evaluated are R+ and R+3. We consider the centrifugal force exerted on the particles due to a fast rotation rate, along with the effects of field‐aligned currents present in the auroral regions. The total number flux from both auroral regions is found to be 5.5–13.0×1027 s−1, which relates to a total mass source of 5.5–17.7 kg s−1. These values are on average an order of magnitude higher than expected without the additional effects of centrifugal force and field‐aligned currents. We find the ionospheric outflow rate to be comparable to the lower estimates of the mass loading rate from Enceladus and are in agreement with recent Cassini observations. This additional mass flux into the magnetosphere can substantially affect the dynamics and composition of the inner and middle magnetosphere of Saturn

    High-Throughput In Vivo Analysis of Gene Expression in Caenorhabditis elegans

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    Using DNA sequences 5′ to open reading frames, we have constructed green fluorescent protein (GFP) fusions and generated spatial and temporal tissue expression profiles for 1,886 specific genes in the nematode Caenorhabditis elegans. This effort encompasses about 10% of all genes identified in this organism. GFP-expressing wild-type animals were analyzed at each stage of development from embryo to adult. We have identified 5′ DNA regions regulating expression at all developmental stages and in 38 different cell and tissue types in this organism. Among the regulatory regions identified are sequences that regulate expression in all cells, in specific tissues, in combinations of tissues, and in single cells. Most of the genes we have examined in C. elegans have human orthologs. All the images and expression pattern data generated by this project are available at WormAtlas (http://gfpweb.aecom.yu.edu/index) and through WormBase (http://www.wormbase.org)

    An Integrated Strategy to Study Muscle Development and Myofilament Structure in Caenorhabditis elegans

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    A crucial step in the development of muscle cells in all metazoan animals is the assembly and anchorage of the sarcomere, the essential repeat unit responsible for muscle contraction. In Caenorhabditis elegans, many of the critical proteins involved in this process have been uncovered through mutational screens focusing on uncoordinated movement and embryonic arrest phenotypes. We propose that additional sarcomeric proteins exist for which there is a less severe, or entirely different, mutant phenotype produced in their absence. We have used Serial Analysis of Gene Expression (SAGE) to generate a comprehensive profile of late embryonic muscle gene expression. We generated two replicate long SAGE libraries for sorted embryonic muscle cells, identifying 7,974 protein-coding genes. A refined list of 3,577 genes expressed in muscle cells was compiled from the overlap between our SAGE data and available microarray data. Using the genes in our refined list, we have performed two separate RNA interference (RNAi) screens to identify novel genes that play a role in sarcomere assembly and/or maintenance in either embryonic or adult muscle. To identify muscle defects in embryos, we screened specifically for the Pat embryonic arrest phenotype. To visualize muscle defects in adult animals, we fed dsRNA to worms producing a GFP-tagged myosin protein, thus allowing us to analyze their myofilament organization under gene knockdown conditions using fluorescence microscopy. By eliminating or severely reducing the expression of 3,300 genes using RNAi, we identified 122 genes necessary for proper myofilament organization, 108 of which are genes without a previously characterized role in muscle. Many of the genes affecting sarcomere integrity have human homologs for which little or nothing is known

    Robust estimation of bacterial cell count from optical density

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    Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

    Healthcare Access and Quality Index based on mortality from causes amenable to personal health care in 195 countries and territories, 1990-2015 : a novel analysis from the Global Burden of Disease Study 2015

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    Background National levels of personal health-care access and quality can be approximated by measuring mortality rates from causes that should not be fatal in the presence of effective medical care (ie, amenable mortality). Previous analyses of mortality amenable to health care only focused on high-income countries and faced several methodological challenges. In the present analysis, we use the highly standardised cause of death and risk factor estimates generated through the Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) to improve and expand the quantification of personal health-care access and quality for 195 countries and territories from 1990 to 2015. Methods We mapped the most widely used list of causes amenable to personal health care developed by Nolte and McKee to 32 GBD causes. We accounted for variations in cause of death certification and misclassifications through the extensive data standardisation processes and redistribution algorithms developed for GBD. To isolate the effects of personal health-care access and quality, we risk-standardised cause-specific mortality rates for each geography-year by removing the joint effects of local environmental and behavioural risks, and adding back the global levels of risk exposure as estimated for GBD 2015. We employed principal component analysis to create a single, interpretable summary measure-the Healthcare Quality and Access (HAQ) Index-on a scale of 0 to 100. The HAQ Index showed strong convergence validity as compared with other health-system indicators, including health expenditure per capita (r= 0.88), an index of 11 universal health coverage interventions (r= 0.83), and human resources for health per 1000 (r= 0.77). We used free disposal hull analysis with bootstrapping to produce a frontier based on the relationship between the HAQ Index and the Socio-demographic Index (SDI), a measure of overall development consisting of income per capita, average years of education, and total fertility rates. This frontier allowed us to better quantify the maximum levels of personal health-care access and quality achieved across the development spectrum, and pinpoint geographies where gaps between observed and potential levels have narrowed or widened over time. Findings Between 1990 and 2015, nearly all countries and territories saw their HAQ Index values improve; nonetheless, the difference between the highest and lowest observed HAQ Index was larger in 2015 than in 1990, ranging from 28.6 to 94.6. Of 195 geographies, 167 had statistically significant increases in HAQ Index levels since 1990, with South Korea, Turkey, Peru, China, and the Maldives recording among the largest gains by 2015. Performance on the HAQ Index and individual causes showed distinct patterns by region and level of development, yet substantial heterogeneities emerged for several causes, including cancers in highest-SDI countries; chronic kidney disease, diabetes, diarrhoeal diseases, and lower respiratory infections among middle-SDI countries; and measles and tetanus among lowest-SDI countries. While the global HAQ Index average rose from 40.7 (95% uncertainty interval, 39.0-42.8) in 1990 to 53.7 (52.2-55.4) in 2015, far less progress occurred in narrowing the gap between observed HAQ Index values and maximum levels achieved; at the global level, the difference between the observed and frontier HAQ Index only decreased from 21.2 in 1990 to 20.1 in 2015. If every country and territory had achieved the highest observed HAQ Index by their corresponding level of SDI, the global average would have been 73.8 in 2015. Several countries, particularly in eastern and western sub-Saharan Africa, reached HAQ Index values similar to or beyond their development levels, whereas others, namely in southern sub-Saharan Africa, the Middle East, and south Asia, lagged behind what geographies of similar development attained between 1990 and 2015. Interpretation This novel extension of the GBD Study shows the untapped potential for personal health-care access and quality improvement across the development spectrum. Amid substantive advances in personal health care at the national level, heterogeneous patterns for individual causes in given countries or territories suggest that few places have consistently achieved optimal health-care access and quality across health-system functions and therapeutic areas. This is especially evident in middle-SDI countries, many of which have recently undergone or are currently experiencing epidemiological transitions. The HAQ Index, if paired with other measures of health-systemcharacteristics such as intervention coverage, could provide a robust avenue for tracking progress on universal health coverage and identifying local priorities for strengthening personal health-care quality and access throughout the world. Copyright (C) The Author(s). Published by Elsevier Ltd.Peer reviewe

    Story Comprehension in Children with ADHD

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    A wealth of research is available examining children\u27s story comprehension. However, little attention has been directed toward understanding the story comprehension of children with attention deficit hyperactivity disorder (ADHD). The present paper attempts to integrate the developmental literature on children\u27s story comprehension with the little that is known about the story comprehension processes of children with ADHD. This review is guided by a network model of story representation that emphasizes the structure of causal and enabling relations between story events. Examination of the available studies indicates that children with ADHD lag behind their peers in their understanding of causal relations, and that their attentional problems may contribute to difficulties in understanding factual information in the preschool years and causally related information in the elementary years. Some evidence also is presented suggesting that children with ADHD are less effective in taking advantage of story structure features in guiding their recall of story events. Suggestions for future research are offered that would elaborate our knowledge of the developmental progression in the processing of complex information by children with ADHD

    Can practice nurses take an increased role in chlamydia testing among young people in Australian general practice?

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    Chlamydia is Australia’s most commonly notifiable sexually transmissible infection and a significant public health problem for young people. To interrupt transmission of chlamydia and prevent complications, regular testing and timely treatment is required. General practice is an important setting in which to increase testing as most young people attend general practice annually and it is where most chlamydia diagnoses are made. However, despite clinical guidelines recommending annual testing of sexually active young adults, testing rates are low. The aim of this thesis is to provide new knowledge about the acceptability and feasibility of an increased role for practice nurses (PNs) in chlamydia testing of young people in Australian general practice, using quantitative and qualitative methods. Four studies were undertaken. The first, a survey of PNs and GPs, found gaps in PNs’ chlamydia knowledge and awareness, but willingness of PNs to take an increased role in chlamydia testing. Studies 2 and 3 involved in-depth interviews with PNs and GPs and found that both health professionals supported the PN role in chlamydia testing. Furthermore, they identified many benefits to PN involvement for patients, GPs and PNs themselves. Factors such as time constraints and GP attitudes were raised as possible barriers by PNs, whilst GPs raised concerns around PNs’ existing workload and funding for their role. Both GPs and PNs identified the provision of education as an essential facilitator to PN testing. The fourth study involved a before and after evaluation of a chlamydia education program tailored for PNs. Among those who participated in education, the quantitative survey demonstrated statistically significant improvements in PNs’ knowledge of chlamydia epidemiology, recommended testing practices and willingness to be involved in testing. In conclusion, research reported in this thesis identified that an increased role for PNs in chlamydia testing in Australia is acceptable to PNs and GPs and education programs are important. However, barriers exist that may impede feasibility and development of that role; some barriers are modifiable, while others may require strategies to overcome; such as new models of funding, changes to pathology ordering requirements and promotion of the PN role in sexual health

    Story Comprehension in Children with ADHD

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    A wealth of research is available examining children\u27s story comprehension. However, little attention has been directed toward understanding the story comprehension of children with attention deficit hyperactivity disorder (ADHD). The present paper attempts to integrate the developmental literature on children\u27s story comprehension with the little that is known about the story comprehension processes of children with ADHD. This review is guided by a network model of story representation that emphasizes the structure of causal and enabling relations between story events. Examination of the available studies indicates that children with ADHD lag behind their peers in their understanding of causal relations, and that their attentional problems may contribute to difficulties in understanding factual information in the preschool years and causally related information in the elementary years. Some evidence also is presented suggesting that children with ADHD are less effective in taking advantage of story structure features in guiding their recall of story events. Suggestions for future research are offered that would elaborate our knowledge of the developmental progression in the processing of complex information by children with ADHD

    Comprehension of Televised Stories by Preschool Children With ADHD

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    Investigated visual attention to and story comprehension of televised stories in 4- to 6-year-old children with attention deficit hyperactivity disorder (ADHD) and comparison children. Half of the children in each group watched the program with toys in the room, and the other half watched without toys. Visual attention to the television was recorded, and story comprehension was assessed by performance on cued recall questions. All children attended significantly less when toys were present, but the difference when toys were present was greater for children with ADHD. The groups did not differ on recall of factual information when toys were absent. When toys were present, the comparison children showed no decrement in performance on factual questions, whereas the performance of children with ADHD was significantly worse. On questions testing causal connections, the children with ADHD performed more poorly than comparison children regardless of whether toys were present. Implications of these results for understanding and treating the academic and social difficulties of children with ADHD are discussed
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