90 research outputs found

    The economic design of a potential tradable permit system for SO2 emissions in the European Union

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    This paper contains two main parts. The first develops the issues of the European acid policy, and sets out the general background of the related regulatory regime. It also gives an overview of the theoretical and actual features of emissions trading mechanisms. It then considers the potential attractiveness of SO2 trading in the EU. This background throws light on the more specific analyses and proposals described in the second part of the paper, which is devoted to a presentation of possible frameworks for SO2 trading in the power generation sector in the EU. In section 2.1., we look at some key design variables. In section 2.2., we present three alternative ways of designing a trading scheme. In section 2.3., we consider specific issues related to zoning and scaling.

    The economic design of a potential tradable permit system for SO2 emissions in the European Union

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    published in European Economy, (Reports and Studies Series) (1), DG 2 of European Commission, 1998,This paper contains two main parts. The first develops the issues of the European acid policy, and sets out the general background of the related regulatory regime. It also gives an overview of the theoretical and actual features of emissions trading mechanisms. It then considers the potential attractiveness of SO2 trading in the EU. This background throws light on the more specific analyses and proposals described in the second part of the paper, which is devoted to a presentation of possible frameworks for SO2 trading in the power generation sector in the EU. In section 2.1., we look at some key design variables. In section 2.2., we present three alternative ways of designing a trading scheme. In section 2.3., we consider specific issues related to zoning and scaling

    Variations in the total nuclear DNA content in African Coffea species (Rubiaceae)

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    La quantité d'ADN totale par noyau a été estimée pour soixante-quinze génotypes de #Coffea appartenant à seize espèces diploïdes (2n=22) et #C. arabica (tétraploïde 2n=44) par cytofluorométrie en flux. L'agent fluorochrome utilisé est l'iodure de propidium (intercalent). La valeur 2C du génome des caféiers varie de 0,9 pg d'ADN par noyau à 1,9 pg. Trois espèces, originaires d'Afrique de l'Est (#C. sessiliflora, C. racemosa et #C. pseudozanguebariae) ont le plus petit génome (environ 1 pg par noyau). A l'opposé, trois espèces de forêt tropicale humide (#C. humilis, C. sp. Moloundou et #C. liberica) correspondent aux valeurs les plus élevées (1,6 pg). L'espèce tétraploïde #C. arabica$, originaire d'Ethiopie, a un génome de 2,5 pg. Au sein des espèces diploïdes, on note une importante variation des valeurs 2C pouvant atteindre 25 % pour une espèce. Les résultats sont comparés aux données analogues chez d'autres Angiospermes et une tentative d'interprétation des variations observées est présentée. (Résumé d'auteur

    Inheritance and restriction fragment length polymorphism of chloroplast DNA in the genus Coffea L.

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    CpDNA variation among 52 tree samples belonging to 25 different taxa of #Coffea and two species of #Psilanthus was assessed by RFLP analysis on both the total chloroplast genome and the atpB-rbcL intergenic region. Twelve variable characters were distinguished allowing the identification of 12 different plastomes. The low sequence divergence observed might suggest that #Coffea is a young genus. The results were in contradiction with the present classification into two genera. Additionally, cpDNA inheritance was studied in interspecific hybrids between #C. arabica and #C. canephora, and in an intraspecific progeny of #C. canephora, using PCR-based markers. Both studies showed exclusively maternal inheritance of cpDNA. (Résumé d'auteur

    Nuclear DNA content in the subgenus Coffea (Rubiaceae) : inter and intra-specific variation in African species

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    La cytométrie en flux a été utilisée pour estimer la quantité d'ADN nucléaire chez 13 espèces de #Coffea (Rubiacea) originaires d'Afrique. Douze espèces diploïdes (#2n=22) et l'espèce tétraploïde #C. arabica (#2n=44) ont été analysées. Pour 77 génotypes, des populations de noyaux isolés ont été colorées par l'iodure de propidium (IP ; non spécifique des bases). Pour trente neuf génotypes, le 4',6-diamidino-2-phenylindole (DAPI; AT spécifique) a été également utilisé. Les quantités 2C d'ADN nucléaire, estimées avec l'IP, oscillent entre 0,95 et 1,78 pg. Trois groupes correspondant à des quantités croissantes d'ADN ont été mis en évidence. Les trois espèces #C. sessiliflora, C. racemosa et #C. pseudozanguebariae se classent dans le groupe des plus petites valeurs (groupe 1 : 0,90 à 1,30 pg). Les trois espèces #C. eugenioides, C. stenophylla et #C. sp. F. se rangent uniquement dans le groupe des valeurs intermédiaires (groupe 2 : 1,31 à 1,60 pg). Les autres espèces se répartissent entre le groupe 2 et le groupe des plus hautes valeurs (groupe 3 : 1,61 à 1,80 pg). Les valeurs déterminées pour les espèces de #Coffea$, sont comparées aux niveaux intra- et inter-spécifique à celles d'autres angiospermes. Les différences observées sont discutées en fonction de l'origine éco-géographique des espèces, leurs caractéristiques phénologiques et la fertilité de leurs hybrides F1 interspécifiques. (Résumé d'auteur

    A search for small noncoding RNAs in Staphylococcus aureus reveals a conserved sequence motif for regulation

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    Bioinformatic analysis of the intergenic regions of Staphylococcus aureus predicted multiple regulatory regions. From this analysis, we characterized 11 novel noncoding RNAs (RsaA‐K) that are expressed in several S. aureus strains under different experimental conditions. Many of them accumulate in the late-exponential phase of growth. All ncRNAs are stable and their expression is Hfq-independent. The transcription of several of them is regulated by the alternative sigma B factor (RsaA, D and F) while the expression of RsaE is agrA-dependent. Six of these ncRNAs are specific to S. aureus, four are conserved in other Staphylococci, and RsaE is also present in Bacillaceae. Transcriptomic and proteomic analysis indicated that RsaE regulates the synthesis of proteins involved in various metabolic pathways. Phylogenetic analysis combined with RNA structure probing, searches for RsaE‐mRNA base pairing, and toeprinting assays indicate that a conserved and unpaired UCCC sequence motif of RsaE binds to target mRNAs and prevents the formation of the ribosomal initiation complex. This study unexpectedly shows that most of the novel ncRNAs carry the conserved C−rich motif, suggesting that they are members of a class of ncRNAs that target mRNAs by a shared mechanis

    A search for small noncoding RNAs in Staphylococcus aureus reveals a conserved sequence motif for regulation

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    Bioinformatic analysis of the intergenic regions of Staphylococcus aureus predicted multiple regulatory regions. From this analysis, we characterized 11 novel noncoding RNAs (RsaA‐K) that are expressed in several S. aureus strains under different experimental conditions. Many of them accumulate in the late-exponential phase of growth. All ncRNAs are stable and their expression is Hfq-independent. The transcription of several of them is regulated by the alternative sigma B factor (RsaA, D and F) while the expression of RsaE is agrA-dependent. Six of these ncRNAs are specific to S. aureus, four are conserved in other Staphylococci, and RsaE is also present in Bacillaceae. Transcriptomic and proteomic analysis indicated that RsaE regulates the synthesis of proteins involved in various metabolic pathways. Phylogenetic analysis combined with RNA structure probing, searches for RsaE‐mRNA base pairing, and toeprinting assays indicate that a conserved and unpaired UCCC sequence motif of RsaE binds to target mRNAs and prevents the formation of the ribosomal initiation complex. This study unexpectedly shows that most of the novel ncRNAs carry the conserved C−rich motif, suggesting that they are members of a class of ncRNAs that target mRNAs by a shared mechanism

    Cartography of Methicillin-Resistant S. aureus Transcripts: Detection, Orientation and Temporal Expression during Growth Phase and Stress Conditions

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    BACKGROUND: Staphylococcus aureus is a versatile bacterial opportunist responsible for a wide spectrum of infections. The severity of these infections is highly variable and depends on multiple parameters including the genome content of the bacterium as well as the condition of the infected host. Clinically and epidemiologically, S. aureus shows a particular capacity to survive and adapt to drastic environmental changes including the presence of numerous antimicrobial agents. Mechanisms triggering this adaptation remain largely unknown despite important research efforts. Most studies evaluating gene content have so far neglected to analyze the so-called intergenic regions as well as potential antisense RNA molecules. PRINCIPAL FINDINGS: Using high-throughput sequencing technology, we performed an inventory of the whole transcriptome of S. aureus strain N315. In addition to the annotated transcription units, we identified more than 195 small transcribed regions, in the chromosome and the plasmid of S. aureus strain N315. The coding strand of each transcript was identified and structural analysis enabled classification of all discovered transcripts. RNA purified at four time-points during the growth phase of the bacterium allowed us to define the temporal expression of such transcripts. A selection of 26 transcripts of interest dispersed along the intergenic regions was assessed for expression changes in the presence of various stress conditions including pH, temperature, oxidative shocks and growth in a stringent medium. Most of these transcripts showed expression patterns specific for the defined stress conditions that we tested. CONCLUSIONS: These RNA molecules potentially represent important effectors of S. aureus adaptation and more generally could support some of the epidemiological characteristics of the bacterium
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