1,491 research outputs found
The digital transformation of Russia: digital skills and its potential
65 percent of children entering primary school today will work in employment that does
not yet exist; and by 2022 approximately 22 percent of employment in the global
economy will be created by digital technologies. 73 percent of company managers say
they have serious problems finding specialists qualified in such technologies,
compared with 10 percent in 2010. This shows the speed of the changes to which
digitalisation is fundamenta
Organic moderator-coolant in-pile irradiation loop for the MIT nuclear reactor : October 1, 1958 to October 1, 1959
Includes bibliographical references (leaf 34)First annual report; to October 1, 1958 to October 1, 1959Work performed under contract with Atomics International of North American Aviation, Inc. N9-S-514Division of Sponsored Research Project no. 8091Atomic Energy Commission contract no. AT(10-1)-106
Radiopyrolysis
Statement of responsibility on title-page reads: E.A. Mason, T.H. Timmins, D.T. Morgan, and W.N. Bley"Issued: October 1966.""MIT-334-70 Reactor Technology."Also issued by T.H. Timmins and supervised by E.A. Mason as an Sc. D. thesis , Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1967Includes bibliographical references (pages A6.1-A6.7)MIT DSR Project no. 79819Work performed for the Savannah River Operations Office, U.S. Atomic Energy Commission under Contract no. AT(38-1)-33
In-pile loop irradiation studies of organic coolant materials : progress report, October 1, 1965 - December 31, 1965
"Issued: April 1, 1966.""AEC Research and Development Report"--Cover"MIT-334-48 ,Reactor Technology, Standard TID 4500."Includes bibliographical references (leaf 28)Progress report; October 1, 1965 - December 31, 1965M.I.T. project no. DSR 9819U.S. Atomic Energy Commission, Savannah River Operations Office contract no. AT(38-1)-33
Crystal structures of Burkholderia cenocepacia dihydropteroate synthase in the apo-form and complexed with the product 7,8-dihydropteroate
<p>Abstract</p> <p>Background</p> <p>The enzyme dihydropteroate synthase (DHPS) participates in the <it>de novo </it>synthesis of folate cofactors by catalyzing the formation of 7,8-dihydropteroate from condensation of <it>p</it>-aminobenzoic acid with 6-hydroxymethyl-7,8-dihydropteroate pyrophosphate. DHPS is absent from humans, who acquire folates from diet, and has been validated as an antimicrobial therapeutic target by chemical and genetic means. The bacterium <it>Burkholderia cenocepacia </it>is an opportunistic pathogen and an infective agent of cystic fibrosis patients. The organism is highly resistant to antibiotics and there is a recognized need for the identification of new drugs against <it>Burkholderia </it>and related Gram-negative pathogens. Our characterization of the DHPS active site and interactions with the enzyme product are designed to underpin early stage drug discovery.</p> <p>Results</p> <p>An efficient recombinant protein expression system for DHPS from <it>B. cenocepacia </it>(<it>Bc</it>DHPS) was prepared, the dimeric enzyme purified in high yield and crystallized. The structure of the apo-enzyme and the complex with the product 7,8-dihydropteroate have been determined to 2.35 Å and 1.95 Å resolution respectively in distinct orthorhombic crystal forms. The latter represents the first crystal structure of the DHPS-pterin product complex, reveals key interactions involved in ligand binding, and reinforces data generated by other structural studies. Comparisons with orthologues identify plasticity near the substrate-binding pocket and in particular a range of loop conformations that contribute to the architecture of the DHPS active site. These structural data provide a foundation for hit discovery. An intriguing observation, an artifact of the analysis, that of a potential sulfenamide bond within the ligand complex structure is mentioned.</p> <p>Conclusion</p> <p>Structural similarities between <it>Bc</it>DHPS and orthologues from other Gram-negative species are evident as expected on the basis of a high level of sequence identity. The presence of 7,8-dihydropteroate in the binding site provides details about ligand recognition by the enzyme and the different states of the enzyme allow us to visualize distinct conformational states of loops adjacent to the active site. Improved drugs to combat infections by <it>Burkholderia sp. </it>and related Gram-negative bacteria are sought and our study now provides templates to assist that process and allow us to discuss new ways of inhibiting DHPS.</p
Friction factor and heat transfer correlation for irradiated organic coolants
"September 1965."Series statement handwritten on cover"MIT-334-23 Chemistry."Also written as an M.S. theses written by the first author and advised by the second author, Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1966Includes bibliographical references (pages 163-165)M.I.T. DSR Project no. 9819Work performed for the Savannah River Operations Office, U.S. Atomic Energy Commission under contract no. AT(38-1)-33
Hyporheic Exchange and Water Chemistry of Two Arctic Tundra Streams of Contrasting Geomorphology
The North Slope of Alaska’s Brooks Range is underlain by continuous permafrost, but an active layer of thawed sediments develops at the tundra surface and beneath streambeds during the summer, facilitating hyporheic exchange. Our goal was to understand how active layer extent and stream geomorphology influence hyporheic exchange and nutrient chemistry. We studied two arctic tundra streams of contrasting geomorphology: a high-gradient, alluvial stream with riffle-pool sequences and a low-gradient, peat-bottomed stream with large deep pools connected by deep runs. Hyporheic exchange occurred to ~50 cm beneath the alluvial streambed and to only ~15 cm beneath the peat streambed. The thaw bulb was deeper than the hyporheic exchange zone in both stream types. The hyporheic zone was a net source of ammonium and soluble reactive phosphorus in both stream types. The hyporheic zone was a net source of nitrate in the alluvial stream, but a net nitrate sink in the peat stream. The mass flux of nutrients regenerated from the hyporheic zones in these two streams was a small portion of the surface water mass flux. Although small, hyporheic sources of regenerated nutrients help maintain the in-stream nutrient balance. If future warming in the arctic increases the depth of the thaw bulb, it may not increase the vertical extent of hyporheic exchange. The greater impacts on annual contributions of hyporheic regeneration are likely to be due to longer thawed seasons, increased sediment temperatures or changes in geomorphology
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