235 research outputs found

    Complete nucleotide sequence and structural organization of pPB1, a small Lactobacillus plantarum cryptic plasmid that originated by modular exchange

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    A small cryptic plasmid designated pPB1 was isolated from Lactobacillus plantarum BIFI-38 and its complete 2899 bp nucleotide sequence was determined. Sequence analysis revealed four putative open reading frames. Based on sequence analysis two modules could be identified. First, the replication module consisted of a sequence coding for a replication protein (RepB) and its corresponding target site, and two putative repressor proteins (RepA and RepC). Sequence analysis indicated the possible synthesis of an antisense RNA that might regulate RepB production. A putative laggingstrand initiation site was also found, suggesting that pPB1 replicates via a rolling circle mechanism. The second module of pPB1 consisted of a sequence coding for a putative mobilization protein and its corresponding oriT site. Since the nucleotide sequence of the replication module showed 94.5% identity to the similar region on the Leuconostoc lactis plasmid pCI411, and the nucleotide sequence of the mobilization module had 97.5% identity to L. plantarum plasmid pLB4, it is concluded that pPB1 originated by modular exchange between two such plasmids by homologous recombination. Putative recombination sites where crossover might have taken place were also identifiedThis work was supported by Grant 07G/0035/2003 from the Comunidad de Madrid and RM03-002 from the Instituto Nacional de Investigación y Tecnologı´a Agraria y Alimentaria (INIA). We thank R. Gonza´lez and A.V. Carrascosa for their advice and critical reading of the manuscript. B. de las Rivas was a recipient of a postdoctoral fellowship and A. Marcobal of a predoctoral fellowship both from the Comunidad de Madrid.Peer reviewe

    Обоснование актуальности использования в трансмиссии геохода эксцентриково-циклоидального зацепления

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    Рассматривается состояние вопроса по темпам формирования подземного пространства в России. Проводится анализ недостатков имеющегося проходческого оборудования (щиты, комбайны). Отмечается, что перспективным способом проведения горных выработок является геовинчестерная технология, базовым функциональным элементом которой является геоход. Утверждается, что одной из ключевых систем геохода, определяющей его работоспособность, является трансмиссия. Отмечается, что реализованная в настоящее время в опытном образце геохода трансмиссия с гидроцилиндрами, имеет, как свои достоинства, так и недостатки. Это не позволяет считать трансмиссию с гидроцилиндрами оптимальным решением для её использования, при разработке геоходов нового поколения. Проводится обзор различных видов зубчатых зацеплений и делаются выводы о перспективности их применения в трансмиссии геохода

    Loss of Potential Aquatic-Terrestrial Subsidies Along the Missouri River Floodplain

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    The floodplains of large rivers have been heavily modified due to riparian development and channel modifications, both of which can eliminate shallow off-channel habitats. The importance of these habitats for aquatic organisms like fishes is well studied. However, loss of off-channel habitat also eliminates habitats for the production of emerging aquatic insects, which subsidize riparian consumers in terrestrial food webs. We used field collections of insect emergence, historical mapping, and statistical modeling to estimate the loss of insect emergence due to channel modifications along eight segments of the Missouri River (USA), encompassing 1566 river km, between 1890 and 2012. We estimate annual production of emerging aquatic insects declined by a median of 36,000 kgC (95% CrI: 3000 to 450,000) between 1890 and 2012 (a 34% loss), due to the loss of surface area in backwaters and related off-channel habitats. Under a conservative assumption that riparian birds obtain 24% of their annual energy budget from adult aquatic insects, this amount of insect loss would be enough to subsidize approximately 790,000 riparan woodland birds during the breeding and nesting period (May to August; 95% CrI: 57,000 to 10,000,000). Most of the loss is concentrated in the lower reaches of the Missouri River, which historically had a wide floodplain, a meandering channel, and a high density of off-channel habitats, but which were substantially reduced due to channelization and bank stabilization. Our results indicate that the loss of off-channel habitats in large river floodplains has the potential to substantially affect energy availability for riparian insectivores, further demonstrating the importance of maintaining and restoring these habitats for linked aquatic-terrestrial ecosystems

    Overview of ASDEX Upgrade results

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    Recent results from the ASDEX Upgrade experimental campaigns 2001 and 2002 are presented. An improved understanding of energy and particle transport emerges in terms of a 'critical gradient' model for the temperature gradients. Coupling this to particle diffusion explains most of the observed behaviour of the density profiles, in particular, the finding that strong central heating reduces the tendency for density profile peaking. Internal transport barriers (ITBs) with electron and ion temperatures in excess of 20 keV (but not simultaneously) have been achieved. By shaping the plasma, a regime with small type II edge localized modes (ELMs) has been established. Here, the maximum power deposited on the target plates was greatly reduced at constant average power. Also, an increase of the ELM frequency by injection of shallow pellets was demonstrated. ELM free operation is possible in the quiescent H-mode regime previously found in DIII-D which has also been established on ASDEX Upgrade. Regarding stability, a regime with benign neoclassical tearing modes (NTMs) was found. During electron cyclotron current drive (ECCD) stabilization of NTMs, βN could be increased well above the usual onset level without a reappearance of the NTM. Electron cyclotron resonance heating and ECCD have also been used to control the sawtooth repetition frequency at a moderate fraction of the total heating power. The inner wall of the ASDEX Upgrade vessel has increasingly been covered with tungsten without causing detrimental effects on the plasma performance. Regarding scenario integration, a scenario with a large fraction of noninductively driven current (≥50%), but without ITB has been established. It combines improved confinement (τE/τITER98 ≈ 1.2) and stability (βN ≤ 3.5) at high Greenwald fraction (ne/nGW ≈ 0.85) in steady state and with type II ELMy edge and would offer the possibility for long pulses with high fusion power at reduced current in ITER
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