1,148 research outputs found
Bicyclobutanes as unusual building blocks for complexity generation in organic synthesis
No full textBicyclobutanes are among the most highly strained organic compounds and are intriguing building blocks in organic synthesis. This review provides an overview of the recent developments in bicyclobutane synthesis, their synthetic utility and their modes of reactivity
Liftings for noncomplete probability spaces
No full textThe current state of knowledge concerning liftings for noncomplete probability spaces is discussed. This is a somewhat expanded version of the author's talk given at the 1991 Summer Conference on General Topology and Applications in Honor of Mary Ellen Rudin and Her Work.PT: S; CR: BURKE MR, IN PRESS P AM MATH S BURKE MR, 1991, ISRAEL J MATH, V73, P33 BURKE MR, 1992, ISRAEL J MATH, V79, P289 CARLSON T, THEOREM LIFTING CHRISTENSEN JPR, 1974, TOPOLOGY BOREL STRUC FREMLIN DH, 1989, HDB BOOLEAN ALGEBRAS, P877 INOESCUTULCEA A, 1966, 5TH P BERK S MATH ST, V2 IONESCUTULCEA A, 1967, CONTRIBUTIONS PROB 1, P63 IONESCUTULCEA A, 1969, TOPICS THEORY LIFTIN JECH TJ, 1978, SET THEORY JOHNSON RA, 1980, P AM MATH SOC, V80, P234 JUST W, IN PRESS T AM MATH S KUPKA J, 1983, INDIANA U MATH J, V32, P717 LOSERT V, 1983, LNM, V1080, P95 MAHARAM D, 1958, P AM MATH SOC, V9, P987 SHELAH S, 1983, ISRAEL J MATH, V45, P90 TALAGRAND M, 1982, P AM MATH SOC, V84, P379 VONNEUMANN J, 1931, CRELLES J MATH, V165, P109; NR: 18; TC: 0; J9: ANN N Y ACAD SCI; PG: 4; GA: BZ86BSource type: Electronic(1
Assessing an Elusive 3,4‐Dimethyl‐Chloroborole
No full textAbstract
The attempted syntheses of 3,4‐dimethylborole derivatives further bearing bulky SiMe2t‐Bu groups in 2,5‐position are reported. Isolation of base‐stabilized adducts to the chloroborole were achieved. The respective free borole was found to be unstable and revealed 1,3‐hydrogen atom shift isomerization to a 1‐bora‐1,3‐butadiene with an s‐trans orientation and lacking cyclic conjugation of the π‐system. Computational probing indicates elevated C−H acidity of methyl groups attached to the butadiene backbone in boroles, exceeding the C−H acidity of respective boron‐bound methyl groups. Derivatization attempts of the new chloroborole are reported.A chloroborole with a new substitution pattern is presented. Methyl groups in the butadiene backbone are revealed to allow rearrangement to form non‐cyclo‐conjugate borabutadienes. The thermodynamic driving force is loss of anti‐aromatic destabilization. Computationally, methyl groups in the backbone of boroles are found to be more C−H acidic than methyl groups attached to the boron atom.
imageFonds der chemischen Industrie is acknowledged for funding (Liebig Fellowship)Boehringer Ingelheim Foundation
Photocatalytic Oxidative Activation of Bicyclo[1.1.0]butanes for Formal [2σ+2π] Cycloadditions
No full textWe report the discovery of an example of oxidative bicyclo[1.1.0]butane activation. This reactivity stands in contrast to well-established strain-release nucleophile addition and reductive activation and opens up further possibilities for exploiting bicyclo[1.1.0]butanes in synthesis. Using a strongly oxidizing acridinium organophotocatalyst, the formal [2σ+2π] cycloaddition between bicyclo[1.1.0]butanes and alkenes or aldehydes leads to the corresponding bicyclo[2.1.1]hexanes or oxabicyclo[2.1.1]hexanes. The subtle interplay between bicyclo[1.1.0]butane and alkene identity dictates the mechanism of the reaction, with regiodivergent pathways providing complementary reaction products in up to >20:1 regioselectivity. A mechanistic investigation including electrochemical, photophysical, radical trapping, and computational studies support the oxidative mechanisms proposed
PROBLEM OF A RATIO OF THE POINTS OF VIEW IN THE NOVEL “FOMA GORDEYEV” BY MAXIM GORKY
No full textVarious points of view of the characters of the novel “Foma Gordeyev” by Maxim Gorky come
to light and are analysed in the article, their complicated ratio supported by certain motives – work or business, dissociation, loneliness, enrichment and search of the place in life – is considered. It is proved that the
ratio of the characters’ points of view understood by the author as positions, from which events are considered, is among the bright artistic touches of early works of Maxim Gorky. This inclusion in the Fin de siècle
era, time of the overall overturn and of the new judgement of many concepts could be used in connection
with unwillingness of Maxim Gorky’s open expression of his author’s opinion. Composing a fancy plot, bringing heroes together, the
writer offers the sooth at the reader’s discretion rather than making emphases. The narrator’s voice is dominating, beginning and finishing the epic narration, at the same time only framing various points of view of the characters. The polyphony of the novel and the
thought-over ratio between the author, the storyteller and the heroes allowed Maxim Gorky creating gallery of living, spatial characters,
emphasising dramatic bases of the Russian life of the represented period and reducing all voices to a uniform denominator. The ratio
of the heroes’ points of view becomes one of the bases of the work’s composition and leads to understanding of the reasons of failures
of many characters. The author of the article analyses ways of introducing the speaking people’s images to the artistic text, emphasises
existence of the special sayings for all occasions in the text designed to influence the recipient by the offer of “wisdom formulas” to it,
only to be taken stock of by the reader. Most likely, the ratio of the points of view in the novel as a special device had, on the one hand,
already been preconditioned, and, on the other hand, could affect a peculiar mosaicity of the upcoming Maxim Gorky’s personal artistic
method. Moreover, features of the narration and substantial aspects of composition allow us saying that in the novel “Foma Gordeyev”,
Maxim Gorky creatively masters and actively uses findings of the Russian classics of the second half of the 19th century
170226 ELDER CARE EVENT BEARD 007
No full textProfessor Laura Olson, a member of the Political Science department at Lehigh, listens to her audience on Wednesday, Feb. 22, 2017 in Williams Hall. Olson is the author of "Elder Care Journey: A View from the Front Lines" (Maxim Beard/B&W Staff
170226 ELDER CARE EVENT BEARD 003
No full textProfessor Laura Olson, author of "Elder Care Journey: A View from the Front Lines", talks during a Brown Bag Series on Wednesday, Feb. 22, 2017 in Williams Hall. Olson is a professor of Political Science at Lehigh. (Maxim Beard/B&W Staff
170226 ELDER CARE EVENT BEARD 005
No full textProfessor Laura Olson, author of "Elder Care Journey: A View from the Front Lines", speaks during a Brown Bag Series on Wednesday, Feb. 22, 2017 in Williams Hall. Olson passionately discussed her personal experience with the long-term care system in the U.S. (Maxim Beard/B&W Staff
An RNA interference knock-down of nitrate reductase enhances lipid biosynthesis in the diatom Phaeodactylum tricornutum
No full textWhen diatoms are stressed for inorganic nitrogen they remodel their intermediate metabolism and redirect carbon towards lipid biosynthesis. However, this response comes at a significant cost reflected in decreased photosynthetic energy conversion efficiency and growth. Here we explore a molecular genetics approach to restrict the assimilation of inorganic nitrogen by knocking down nitrate reductase (NR). The transformant strain, NR21, exhibited about 50% lower expression and activity of the enzyme but simultaneously accumulated over 40% more fatty acids. However, in contrast to nitrogen-stressed wild-type (WT) cells, which grow at about 20% of the rate of nitrogen-replete cells, growth of NR21 was only reduced by about 30%. Biophysical analyses revealed that the photosynthetic energy conversion efficiency of photosystem II was unaffected in NR21; nevertheless, the plastoquinone pool was reduced by 50% at the optimal growth irradiance while in the WT it was over 90% oxidized. Further analyses reveal a 12-fold increase in the glutamate/glutamine ratio and an increase NADPH and malonyl-CoA pool size. Transcriptomic analyses indicate that the knock down resulted in changes in the expression of genes for lipid biosynthesis, as well as the expression of specific transcription factors. Based on these observations, we hypothesize that the allocation of carbon and reductants in diatoms is controlled by a feedback mechanism between intermediate metabolites, the redox state of the plastid and the expression and binding of transcription factors related to stress responses.Peer reviewe
Contribution of Citizen Science to Biodiversity Data Mobilization in Russia
No full textPresentation for TDWG 2020 - A Virtual Conference
Session: CO03, 22 October 2020
Conference Abstract: https://doi.org/10.3897/biss.4.59197
video: https://youtu.be/dOp6j69qxT4Presenting author: Maxim Shashko
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