104 research outputs found

    Ventilation coefficient trends in the recent decades over four major Indian metropolitan cities

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    Thirty years radiosonde data (1971-2000) at 00 UTC for winter months over four major Indian metros, viz., Mumbai, Delhi, Kolkata and Chennai is analysed to study the trends and long term variations in ventilation coefficients and the consequences on the air quality due to these variations in the four metros. A decreasing trend in ventilation coefficient is observed in all the four metros during the 30 years period indicating increasing pollution potential and a degradation in the air quality over these urban centers. In Delhi, the ventilation coefficient decreased at the rate of 49 and 32 m2/s/year in the months of December and February, respectively during the 30-year period. In Mumbai, the average decrease in ventilation coefficient in winter months is about 15 m2/s/year whereas for Kolkata it is 14 and 17 m2/s/year in December and February, respectively. A decreasing trend in ventilation coefficient is observed in Chennai too although it is not significant. The decreasing ventilation coefficient increased the ground level pollution thereby deteriorating the air quality for the urban population. For Mumbai and Kolkata, decreasing mixing depths and decreasing wind speed contributed to the decreasing ventilation coefficient whereas for Delhi and Chennai decreasing wind speed was responsible for the decrease in ventilation coefficient. Further, the pollution potential was much higher in Delhi which is an inland station as compared to Mumbai, Kolkata and Chennai which are coastal stations under the influence of marine environment. Compared to Delhi, the pollution potential over these three metros was lower as the prevailing sea-breeze helped in the dispersal of pollutants thereby reducing their ground level concentration

    Carbon dioxide and water vapour characteristics on the west coast of Arabian Sea during Indian summer monsoon

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    Carbon dioxide, water vapour, air temperature and wind measurements at 10 Hz sampling rate were carried out over the coast of Arabian Sea, Goa (15°21'N, 73°51'E) in India. These observations were collected, in association with the surface layer turbulent parameters for the Arabian Sea Monsoon Experiment (ARMEX). In the summer monsoon period, concentration of CO 2 was in the range of 550-790 mg m -3 whereas the water vapour was in the range of 17.5-24.5 g m -3. The Fast Fourier Transform (FFT) analysis has been performed on these observations to investigate the spectral behaviour of CO 2 and water vapour. The relation between CO 2 and water vapour on various atmospheric scales has been proposed. CO 2 and water vapour observations confirmed the existence of periodicities of large (11, 8 days), meso (5 days) and micrometeorological (20 min) scales

    Total column ozone variations over oceanic region around Indian sub-continent during pre-monsoon of 2006

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    International audienceSpecial campaign mode ship-based sun photometric observations of total column ozone over the oceanic regions around the Indian sub-continent (56° E?6° E, 4° N?° N) during the pre-monsoon period (18 March?11 May) of 2006 have been used to investigate the spatial and temporal distributions. The overall mean ozone content over the sea region during this period is 298 DU with a variability of ±10 DU. There is a well defined diurnal (daytime) variation in total column ozone with maximum content around the noon-time hours. The amplitude of diurnal variation is higher over the Arabian Sea compared to that over Bay of Bengal. Spatial distribution of total ozone shows higher values over the Head Bay (North Bay of Bengal) and all along the west coast of India strongly pointing to continental origin of possible anthropogenic source. This is further corroborated from the spatial distribution of simultaneously measured aerosol optical thickness (AOT, at 1020 nm) and precipitable water. The overall mean AOT over the oceanic region is 0.09 and mean precipitable water (water vapor) over Indian Ocean region was 3.25 cm which is almost 1 cm higher than that observed over Bay of Bengal and Arabian Sea during the above pre-monsoon period

    AxSpA patients who also meet criteria for fibromyalgia:Identifying distinct patient clusters using data from a UK national register (BSRBR-AS)

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    Background: Around 1 in 8 patients with axial spondyloarthritis (axSpA) also meet criteria for fibromyalgia and such patients have considerable unmet need. Identifying effective therapy is important but to what extent fibromyalgia-like symptoms relate to axSpA disease severity has not been established. The aim of the current analysis was to determine whether distinct clusters of axSpA patients exist and if so to determine a) whether they differ in terms of prevalence of fibromyalgia and b) the features of patients in clusters with high prevalence. Methods: The British Society for Rheumatology Biologics Register (BSRBR-AS) recruited axSpA patients from 83 centres 2012-2017. Clinical data, and information from patients was collected (including research criteria for fibromyalgia). Cluster analysis was undertaken using split samples for development and validation both in the whole population and the sub-group which met fibromyalgia criteria. Results: One thousand three hundred thirty-eight participants were included of whom 23% met research criteria for fibromyalgia. Four clusters were identified. Two exhibited very high disease activity, one which was primarily axial (n = 347) and a smaller cluster (n = 32) with axial and peripheral disease, and in both groups more than half of members met criteria for fibromyalgia. The remaining two clusters (n = 437, n = 462) had overall less severe disease however the one which showed greater disease activity and poorer quality of life had a higher proportion meeting fibromyalgia criteria (16% v. 4%). Within those meeting fibromyalgia criteria there were three clusters. The two main groups were defined by level of symptom severity with a smaller third cluster noted to have high average swollen and tender joint counts and high levels of comorbidity. Conclusions: The major feature defining clusters with a high proportion of persons meeting criteria for fibromyalgia is high axSpA disease activity although clusters with features of fibromyalgia in the absence of high disease activity also show moderately high prevalence. Management may be most successful with pharmacologic therapy to target inflammation but enhanced by the concurrent use of non-pharmacologic therapy in such patients

    Correlating activity and defects in (photo)electrocatalysts using in-situ transient optical microscopy

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    (Photo)electrocatalysts capture sunlight and use it to drive chemical reactions such as water splitting to produce H2. A major factor limiting photocatalyst development is their large heterogeneity which spatially modulates reactivity and precludes establishing robust structure-function relationships. To make such links requires simultaneously probing of the electrochemical environment at microscopic length scales (nm to um) and broad timescales (ns to s). Here, we address this challenge by developing and applying in-situ steady-state and transient optical microscopies to directly map and correlate local electrochemical activity with hole lifetimes, oxygen vacancy concentration and the photoelectrodes crystal structure. Using this combined approach alongside spatially resolved X-Ray absorption measurements, we study microstructural and point defects in prototypical hematite (Fe2O3) photoanodes. We demonstrate that regions of Fe2O3, adjacent to microstructural cracks have a better photoelectrochemical response and reduced back electron recombination due to an optimal oxide vacancy concentration, with the film thickness and carbon impurities also dramatically influencing activity in a complex manner. Our work highlights the importance of microscopic mapping to understand activity and the impact of defects in even, seemingly, homogeneous solid-state metal oxide photoelectrodes

    Three microarray platforms: an analysis of their concordance in profiling gene expression

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    BACKGROUND: Microarrays for the analysis of gene expression are of three different types: short oligonucleotide (25–30 base), long oligonucleotide (50–80 base), and cDNA (highly variable in length). The short oligonucleotide and cDNA arrays have been the mainstay of expression analysis to date, but long oligonucleotide platforms are gaining in popularity and will probably replace cDNA arrays. As part of a validation study for the long oligonucleotide arrays, we compared and contrasted expression profiles from the three formats, testing RNA from six different cell lines against a universal reference standard. RESULTS: The three platforms had 6430 genes in common. In general, correlation of gene expression levels across the platforms was good when defined by concordance in the direction of expression difference (upregulation or downregulation), scatter plot analysis, principal component analysis, cell line correlation or quantitative RT-PCR. The overall correlations (r values) between platforms were in the range 0.7 to 0.8, as determined by analysis of scatter plots. When concordance was measured for expression ratios significant at p-values of <0.05 and at expression threshold levels of 1.5 and 2-fold, the agreement among the platforms was very high, ranging from 93% to 100%. CONCLUSION: Our results indicate that the long oligonucleotide platform is highly suitable for expression analysis and compares favorably with the cDNA and short oligonucleotide varieties. All three platforms can give similar and reproducible results if the criterion is the direction of change in gene expression and minimal emphasis is placed on the magnitude of change

    The Reproducibility of Lists of Differentially Expressed Genes in Microarray Studies

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    Reproducibility is a fundamental requirement in scientific experiments and clinical contexts. Recent publications raise concerns about the reliability of microarray technology because of the apparent lack of agreement between lists of differentially expressed genes (DEGs). In this study we demonstrate that (1) such discordance may stem from ranking and selecting DEGs solely by statistical significance (P) derived from widely used simple t-tests; (2) when fold change (FC) is used as the ranking criterion, the lists become much more reproducible, especially when fewer genes are selected; and (3) the instability of short DEG lists based on P cutoffs is an expected mathematical consequence of the high variability of the t-values. We recommend the use of FC ranking plus a non-stringent P cutoff as a baseline practice in order to generate more reproducible DEG lists. The FC criterion enhances reproducibility while the P criterion balances sensitivity and specificity

    Influence of co-morbid fibromyalgia on disease activity measures and response to tumour necrosis factor inhibitors in axial spondyloarthritis: Results from a UK national register

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    Objective: To quantify the extent to which co-morbid FM is associated with higher disease activity, worse quality of life (QoL) and poorer response to TNF inhibitors (TNFis) in patients with axial SpA. Methods: A prospective study recruiting across 83 centres in the UK. Clinical information and patient-reported measures were available, including 2011 criteria for FM. Multivariable linear regression was used to model the effect of meeting the FM criteria on disease activity, QoL and response to TNFis. Results: A total of 1757 participants were eligible for analyses, of whom 22.1% met criteria for FM. Those with co-morbid FM criteria had higher disease activity [BASDAI average difference FM+ - FM- 1.04 (95% CI 0.75, 1.33)] and worse QoL [Ankylosing Spondylitis Quality of Life score difference 1.42 (95% CI 0.88, 1.96)] after adjusting for demographic, clinical and lifestyle factors. Among 291 participants who commenced biologic therapy, BASDAI scores in those with co-morbid FM were 2.0 higher at baseline but decreased to 1.1 higher at 12 months. There was no significant difference in the likelihood of meeting Assessment of SpondyloArthritis international Society 20 criteria at 12 months. Less improvement in disease activity and QoL over 3 months of TNFi therapy was most strongly related to high scores on the FM criteria symptom severity scale component. Conclusion: Fulfilling criteria for FM has a modest impact on the assessment of axial SpA disease activity and QoL and does not significantly influence response to biologic therapy. Those with a high symptom severity scale on FM assessment may benefit from additional specific management for FM

    The balance of reproducibility, sensitivity, and specificity of lists of differentially expressed genes in microarray studies

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    <p>Abstract</p> <p>Background</p> <p>Reproducibility is a fundamental requirement in scientific experiments. Some recent publications have claimed that microarrays are unreliable because lists of differentially expressed genes (DEGs) are not reproducible in similar experiments. Meanwhile, new statistical methods for identifying DEGs continue to appear in the scientific literature. The resultant variety of existing and emerging methods exacerbates confusion and continuing debate in the microarray community on the appropriate choice of methods for identifying reliable DEG lists.</p> <p>Results</p> <p>Using the data sets generated by the MicroArray Quality Control (MAQC) project, we investigated the impact on the reproducibility of DEG lists of a few widely used gene selection procedures. We present comprehensive results from inter-site comparisons using the same microarray platform, cross-platform comparisons using multiple microarray platforms, and comparisons between microarray results and those from TaqMan – the widely regarded "standard" gene expression platform. Our results demonstrate that (1) previously reported discordance between DEG lists could simply result from ranking and selecting DEGs solely by statistical significance (<it>P</it>) derived from widely used simple <it>t</it>-tests; (2) when fold change (FC) is used as the ranking criterion with a non-stringent <it>P</it>-value cutoff filtering, the DEG lists become much more reproducible, especially when fewer genes are selected as differentially expressed, as is the case in most microarray studies; and (3) the instability of short DEG lists solely based on <it>P</it>-value ranking is an expected mathematical consequence of the high variability of the <it>t</it>-values; the more stringent the <it>P</it>-value threshold, the less reproducible the DEG list is. These observations are also consistent with results from extensive simulation calculations.</p> <p>Conclusion</p> <p>We recommend the use of FC-ranking plus a non-stringent <it>P </it>cutoff as a straightforward and baseline practice in order to generate more reproducible DEG lists. Specifically, the <it>P</it>-value cutoff should not be stringent (too small) and FC should be as large as possible. Our results provide practical guidance to choose the appropriate FC and <it>P</it>-value cutoffs when selecting a given number of DEGs. The FC criterion enhances reproducibility, whereas the <it>P </it>criterion balances sensitivity and specificity.</p
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