On the origin of tropospheric O₃ over the Indian Ocean during the winter monsoon: African biomass burning vs. stratosphere-troposphere exchange

This study investigates the origin of a commonly observed feature in the O₃ profiles: mid tropospheric O₃ maxima (300--500 hPa) over the tropical Indian Ocean. A comparison and analysis of model simulations, using a 3-D global climate-chemistry model, and measured O₃ profiles from the INDOEX campaign is presented. European Centre for Medium-Range Weather Forecast (ECMWF) meteorological analyses have been assimilated into the 3-D model to represent actual meteorology. The model realistically simulates the observed mid-tropospheric O₃ maxima. The analysis of the model simulations shows that the major source of the mid-tropospheric O₃maxima is advection of polluted air masses from continental biomass burning areas over Africa, with generally only a small contribution of stratospheric O₃. Previous studies hinted at stratosphere-troposphere exchange (STE) along the subtropical jet (STJ) as the primary source of the mid-tropospheric O₃ maxima over the Indian Ocean. Analysis of the model simulations shows that the mechanism causing the mid-tropospheric transport of African biomass burning pollution and stratospheric air masses are frontal zones or waves passing along the subtropical jets, causing advection of tropical air masses in the prefrontal (equatorward) zone. Furthermore, the frontal zones or waves also cause STE at the poleward side of the STJ. The model simulations also indicate that the contribution of STE in general is minor compared to advection and in situ tropospheric production of O₃ for the mid-tropospheric O₃ budget over the Indian Ocean region

Оппозиция концептов жизнь-смерть в смысловой организации петербургского текста русской культуры

Цель исследования – рассмотрение ведущей для организации Петербургского текста оппозиции концептов жизнь-смерть, члены которой получают репрезентацию в составляющих единство текстах А.С. Пушкина, Н.В. Гоголя, Ф.М. Достоевского, А.А. Блока, А.А. Ахматовой, О.Э. Мандельштама, Т.Н. Толстой и др. и участвуют в создании их общего смыслового пространства. Данные концепты оказываются ключевыми для понимания сверхтекста, герои которого вынуждены выбирать между смертью и жизнью, полной страданий.The article is devoted to the opposition of concepts life-death that plays the main part in Petersburg text’s organization. These concepts appear in texts written by A.S. Pushkin, N.V. Gogol, P.M. Dostoevsky, A.A. Blok, A.A. Ahmatova, O.E. Mandelshtam, T.N. Tolstaya etc. and help to unite their semantic space. The analysis of concepts life-death is necessary to understand the super-text which main characters have to choose between death and hard life

Engaging without over-powering: A case study of a FLOSS project

This is the post-print version of the published chapter. The original publication is available at the link below. Copyright @ 2010 IFIP International Federation for Information Processing.The role of Open Source Software (OSS) in the e-learning business has become more and more fundamental in the last 10 years, as long as corporate and government organizations have developed their educational and training programs based on OSS out-of-the-box tools. This paper qualitatively documents the decision of the largest UK e-learning provider, the Open University, to adopt the Moodle e-learning system, and how it has been successfully deployed in its site after a multi-million investment. A further quantitative study also provides evidence of how a commercial stakeholder has been engaged with, and produced outputs for, the Moodle community. Lessons learned from this experience by the stakeholders include the crucial factors of contributing to the OSS community, and adapting to an evolving technology. It also becomes evident how commercial partners helped this OSS system to achieve the transition from an “average” OSS system to a successful multi-site, collaborative and community-based OSS project

DNA methylation dynamics during intestinal stem cell differentiation reveals enhancers driving gene expression in the villus

Background: DNA methylation is of pivotal importance during development. Previous genome-wide studies identified numerous differentially methylated regions upon differentiation of stem cells, many of them associated with transcriptional start sites. Results: We present the first genome-wide, single-base-resolution view into DNA methylation dynamics during differentiation of a mammalian epithelial stem cell: the mouse small intestinal Lgr5+ stem cell. Very little change was observed at transcriptional start sites and our data suggest that differentiation-related genes are already primed for expression in the stem cell. Genome-wide, only 50 differentially methylated regions were identified. Almost all of these loci represent enhancers driving gene expression in the differentiated part of the small intestine. Finally, we show that binding of the transcription factor Tcf4 correlates with hypo-methylation and demonstrate that Tcf4 is one of the factors contributing to formation of differentially methylated regions. Conclusions: Our results reveal limited DNA methylation dynamics during small intestine stem cell differentiation and an impact of transcription factor binding on shaping the DNA methylation landscape during differentiation of stem cells in vivo

Quantitative analysis of chromatin interaction changes upon a 4.3 Mb deletion at mouse 4E2

BACKGROUND: Circular chromosome conformation capture (4C) has provided important insights into three dimensional (3D) genome organization and its critical impact on the regulation of gene expression. We developed a new quantitative framework based on polymer physics for the analysis of paired-end sequencing 4C (PE-4Cseq) data. We applied this strategy to the study of chromatin interaction changes upon a 4.3 Mb DNA deletion in mouse region 4E2. RESULTS: A significant number of differentially interacting regions (DIRs) and chromatin compaction changes were detected in the deletion chromosome compared to a wild-type (WT) control. Selected DIRs were validated by 3D DNA FISH experiments, demonstrating the robustness of our pipeline. Interestingly, significant overlaps of DIRs with CTCF/Smc1 binding sites and differentially expressed genes were observed. CONCLUSIONS: Altogether, our PE-4Cseq analysis pipeline provides a comprehensive characterization of DNA deletion effects on chromatin structure and function

A model perspective on total tropospheric O-3 column variability and implications for satellite observations

In recent years several methods have been developed that derive total tropospheric 03 columns from satellite measurements. However, one issue that has not been paid much attention to is the interpretation of (extratropical) total tropospheric O3 columns. Different processes contribute to the total tropospheric 03 column: stratosphere-troposphere exchange, tropospheric O 3 production and loss, transport and the height of the tropopause. Each process contributes differently to the total tropospheric O3 column variability depending on season, geographical location, and altitude. This paper investigates the contribution of these different processes on total tropospheric O3 column variability using a chemistry-climate model simulation of tropospheric 03, and reflects on the implications for total tropospheric 03 column measurements. On the basis of tropospheric 03 column (satellite) measurements and without other sources of information (e.g., model simulations, observations of other trace species) it is not possible to determine the separate contributions by the aforementioned processes to the extratropical total tropospheric 03 column variability. Furthermore, typical extratropical synoptic-scale (daily) total tropospheric 03 column variability is of the order of 10 DU (1-σ value), implying the errors in (satellite) measurements should be of the order of magnitude at maximum (~10 DU) for daily measurements. For tropical total tropospheric O3 column (satellite) measurements the requirements are less stringent because the most important variability occurs on seasonal timescales. Errors in tropical total tropospheric 03 column (TTOC) measurements should be of the order of 5 DU for monthly means. Copyright 2005 by the American Geophysical Union