Modelagem de Central Termelétrica à Vapor para Simulação Dinâmica

Centrais termelétricas a vapor são capazes de utilizar biomassa e fazer o reaproveitamento de resíduos agrícolas, resíduos urbanos ou subprodutos industriais para produzir energia elétrica, condicionadas aos seus projetos. Este trabalho tem como objetivos representar, por meio de modelos matemáticos, os principais componentes que constituem o circuito de vapor de uma planta de geração termelétrica a vapor, com foco em caldeira aquatubular, e apresentar uma avaliação dos diversos modelos encontrados na literatura de referência, visando dar suporte ao desenvolvimento de aplicações de simulação dinâmica. Os modelos apresentados abrangem a conversão da energia térmica em energia mecânica e a conversão da energia mecânica em energia elétrica. O conhecimento das características das respostas dinâmicas dos componentes de uma central termelétrica é importante para a análise de estabilidade e para o projeto do sistema de controle. A partir dos modelos dinâmicos do processo é possível a realização de testes de estratégias de controle que, interagindo com os modelos da planta, possibilitem identificar previamente o comportamento dinâmico esperado. Este trabalho também pode ser utilizado como uma referência básica para o desenvolvimento de um simulador com finalidade de treinamento de operadores, cuja aplicação possibilita que seja feita a integração total do operador aos procedimentos operacionais, antes mesmo da partida da planta, ampliando a sua capacidade de aprendizagem

Association of mutation patterns in gyrA/B genes and ofloxacin resistance levels in Mycobacterium tuberculosis isolates from East China in 2009

<p>Abstract</p> <p>Background</p> <p>This study aimed to analyze the association of mutation patterns in <it>gyrA </it>and <it>gyrB </it>genes and the ofloxacin resistance levels in clinical <it>Mycobacterium tuberculosis </it>isolates sampled in 2009 from East China.</p> <p>Methods</p> <p>The quinolone resistance-determining region of <it>gyrA/B </it>were sequenced in 192 <it>M. tuberculosis </it>clinical isolates and the minimal inhibitory concentrations (MICs) of 95 ofloxacin-resistant <it>M. tuberculosis </it>isolates were determined by using microplate nitrate reductase assays.</p> <p>Results</p> <p>Mutations in <it>gyrA </it>(codons 90, 91 and 94) and in <it>gyrB </it>(G551R, D500N, T539N, R485C/L) were observed in 89.5% (85/95) and 11.6% (11/95) of ofloxacin-resistant strains, respectively. The <it>gyrB </it>mutations G551R and G549D were observed in 4.1% (4/97) of ofloxacin-susceptible strains and no mutation was found in <it>gyrA </it>in ofloxacin-susceptible strains. The MICs of all ofloxacin-resistant strains showed no significant difference among strains with mutations at codons 90, 91 or 94 in <it>gyrA </it>(F = 1.268, <it>p </it>= 0.287). No differences were detected among strains with different amino acid mutations in the quinolone resistance-determining region of <it>gyrA </it>(F = 1.877, <it>p </it>= 0.123). The difference in MICs between ofloxacin-resistant strains with mutations in <it>gyrA </it>only and ofloxacin-resistant strains with mutations in both <it>gyrA </it>and <it>gyrB </it>genes was not statistically significant (F = 0.549, <it>p </it>= 0.461).</p> <p>Conclusions</p> <p>Although <it>gyrA/B </it>mutations can lead to ofloxacin resistance in <it>M. tuberculosis</it>, there were no associations of different mutation patterns in <it>gyrA/B </it>and the level of ofloxacin resistance in <it>M. tuberculosis </it>isolates from East China in 2009.</p

Structural Insights into the Quinolone Resistance Mechanism of Mycobacterium tuberculosis DNA Gyrase

Mycobacterium tuberculosis DNA gyrase, an indispensable nanomachine involved in the regulation of DNA topology, is the only type II topoisomerase present in this organism and is hence the sole target for quinolone action, a crucial drug active against multidrug-resistant tuberculosis. To understand at an atomic level the quinolone resistance mechanism, which emerges in extensively drug resistant tuberculosis, we performed combined functional, biophysical and structural studies of the two individual domains constituting the catalytic DNA gyrase reaction core, namely the Toprim and the breakage-reunion domains. This allowed us to produce a model of the catalytic reaction core in complex with DNA and a quinolone molecule, identifying original mechanistic properties of quinolone binding and clarifying the relationships between amino acid mutations and resistance phenotype of M. tuberculosis DNA gyrase. These results are compatible with our previous studies on quinolone resistance. Interestingly, the structure of the entire breakage-reunion domain revealed a new interaction, in which the Quinolone-Binding Pocket (QBP) is blocked by the N-terminal helix of a symmetry-related molecule. This interaction provides useful starting points for designing peptide based inhibitors that target DNA gyrase to prevent its binding to DNA

Expression, maturation and turnover of DrrS, an unusually stable, DosR regulated small RNA in Mycobacterium tuberculosis

Mycobacterium tuberculosis depends on the ability to adjust to stresses encountered in a range of host environments, adjustments that require significant changes in gene expression. Small RNAs (sRNAs) play an important role as post-transcriptional regulators of prokaryotic gene expression, where they are associated with stress responses and, in the case of pathogens, adaptation to the host environment. In spite of this, the understanding of M. tuberculosis RNA biology remains limited. Here we have used a DosR-associated sRNA as an example to investigate multiple aspects of mycobacterial RNA biology that are likely to apply to other M. tuberculosis sRNAs and mRNAs. We have found that accumulation of this particular sRNA is slow but robust as cells enter stationary phase. Using reporter gene assays, we find that the sRNA core promoter is activated by DosR, and we have renamed the sRNA DrrS for DosR Regulated sRNA. Moreover, we show that DrrS is transcribed as a longer precursor, DrrS+, which is rapidly processed to the mature and highly stable DrrS. We characterise, for the first time in mycobacteria, an RNA structural determinant involved in this extraordinary stability and we show how the addition of a few nucleotides can lead to acute destabilisation. Finally, we show how this RNA element can enhance expression of a heterologous gene. Thus, the element, as well as its destabilising derivatives may be employed to post-transcriptionally regulate gene expression in mycobacteria in combination with different promoter variants. Moreover, our findings will facilitate further investigations into the severely understudied topic of mycobacterial RNA biology and into the role that regulatory RNA plays in M. tuberculosis pathogenesis

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

European Forest Accounts - Années 2014-2015.

AgroParisTech, représenté par le Laboratoire d’Economie Forestière (LEF) devenu le Bureau d’Economie Théorique et Appliquée (BETA) au 1er janvier 2018, réalise en collaboration avec l’IGN (institut national de l’information géographique et forestière) les comptes européens de la forêts (European Forest Accounts – EFA) pour le compte du Ministère en charge de l’Environnement. Ces EFA sont un ensemble cohérent de tableaux comptables sur la ressource forestière et la filière bois, qui intègrent économie et environnement. Ce rapportage est basé sur le volontariat et son format est défini au niveau européen. Le présent rapport d’étude porte sur les années 2014 et 2015. Il explicite les recommandations d’Eurostat, la méthode utilisée pour compléter les tableaux et une brève analyse des résultats

European Forest Accounts - Années 2016-2017. Rapport d’étude

European Forest Accounts - Années 2016-2017. Rapport d’étud

European Forest Accounts - Années 2014-2015.

AgroParisTech, représenté par le Laboratoire d’Economie Forestière (LEF) devenu le Bureau d’Economie Théorique et Appliquée (BETA) au 1er janvier 2018, réalise en collaboration avec l’IGN (institut national de l’information géographique et forestière) les comptes européens de la forêts (European Forest Accounts – EFA) pour le compte du Ministère en charge de l’Environnement. Ces EFA sont un ensemble cohérent de tableaux comptables sur la ressource forestière et la filière bois, qui intègrent économie et environnement. Ce rapportage est basé sur le volontariat et son format est défini au niveau européen. Le présent rapport d’étude porte sur les années 2014 et 2015. Il explicite les recommandations d’Eurostat, la méthode utilisée pour compléter les tableaux et une brève analyse des résultats

European Forest Accounts. Années 2013 et 2014. Note de méthode [Phase 3]

il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : REPORTEuropean Forest Accounts. Années 2013 et 2014. Note de méthode [Phase 3