668 research outputs found
Measurements of the reaction of antiproton annihilation at rest at three hydrogen target densities
The proton-antiproton annihilation at rest into the final state
was measured for three different target densities: liquid hydrogen, gaseous
hydrogen at NTP and at a low pressure of 5 mbar. The yield of this reaction in
the liquid hydrogen target is smaller than in the low-pressure gas target. The
branching ratios of the channel were calculated on the basis of
simultaneous analysis of the three data samples. The branching ratio for
annihilation into from the protonium state turns out to be
about ten times smaller as compared to the one from the state.Comment: 10 pages, 3 Postscript figures. Accepted by Physics Letters
New data on OZI rule violation in bar{p}p annihilation at rest
The results of a measurement of the ratio R = Y(phi pi+ pi-) / Y(omega pi+
pi-) for antiproton annihilation at rest in a gaseous and in a liquid hydrogen
target are presented. It was found that the value of this ratio increases with
the decreasing of the dipion mass, which demonstrates the difference in the phi
and omega production mechanisms. An indication on the momentum transfer
dependence of the apparent OZI rule violation for phi production from the 3S1
initial state was found.Comment: 11 pages, 3 PostScript figures, submitted to Physics Letter
Review: Allelochemicals as multi-kingdom plant defence compounds: towards an integrated approach
© 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. The capability of synthetic pesticides to manage weeds, insect pests and pathogens in crops has diminished due to evolved resistance. Sustainable management is thus becoming more challenging. Novel solutions are needed and, given the ubiquity of biologically active secondary metabolites in nature, such compounds require further exploration as leads for novel crop protection chemistry. Despite improving understanding of allelochemicals, particularly in terms of their potential for use in weed control, their interactions with multiple biotic kingdoms have to date largely been examined in individual compounds and not as a recurrent phenomenon. Here, multi-kingdom effects in allelochemicals are introduced by defining effects on various organisms, before exploring current understanding of the inducibility and possible ecological roles of these compounds with regard to the evolutionary arms race and dose–response relationships. Allelochemicals with functional benefits in multiple aspects of plant defence are described. Gathering these isolated areas of science under the unified umbrella of multi-kingdom allelopathy encourages the development of naturally-derived chemistries conferring defence to multiple discrete biotic stresses simultaneously, maximizing benefits in weed, insect and pathogen control, while potentially circumventing resistance. © 2020 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry
High-Throughput Phenotypic Screening and Machine Learning Methods Enabled the Selection of Broad-Spectrum Low-Toxicity Antitrypanosomatidic Agents
Broad-spectrum anti-infective chemotherapy agents with activity against Trypanosomes, Leishmania, and Mycobacterium tuberculosis species were identified from a high-throughput phenotypic screening program of the 456 compounds belonging to the Ty-Box, an in-house industry database. Compound characterization using machine learning approaches enabled the identification and synthesis of 44 compounds with broad-spectrum antiparasitic activity and minimal toxicity against Trypanosoma brucei, Leishmania Infantum, and Trypanosoma cruzi. In vitro studies confirmed the predictive models identified in compound 40 which emerged as a new lead, featured by an innovative N-(5-pyrimidinyl)-benzenesulfonamide scaffold and promising low micromolar activity against two parasites and low toxicity. Given the volume and complexity of data generated by the diverse high-throughput screening assays performed on the compounds of the Ty-Box library, the chemoinformatic and machine learning tools enabled the selection of compounds eligible for further evaluation of their biological and toxicological activities and aided in the decision-making process toward the design and optimization of the identified lead
Um dia todos seremos Montag
Partindo de conversa comum em que a menção de Guernica causou constrangimento, pois as pessoas nĂŁo conheciam o quadro, discutimos o caráter educacional especializado, em que os campos gerais do conhecimento nĂŁo sĂŁo valorizados. Isto denota falta de leitura que, quando praticada, Ă© mero consumo. A escola tenta desenvolver esta prática, mas erra na concepção do ler e no nĂŁo atendimento Ă s necessidades do aluno. O professor nĂŁo cumpre o papel de mediador, nem mostra a leitura como superação de dogmas. É urgente rever a polĂtica curricular, presa Ă cultura hegemĂ´nica. Assim, a escola deve abrir-se ao multiculturalismo, revelar a flutuação dos conceitos culturais. Na arte, tem de ensinar como esta nĂŁo se faz cumprindo regras, mas rompendo-as, ao lado do que, o aluno aprenderá que cultura Ă© crise. Percebendo isso, terá conhecimento de sua subjetividade como processo em construção e cultura como interdependĂŞncia. Arte nĂŁo Ă© sagrada. Desmistificando mitos, o aluno está em condições de ser o modelador de sua histĂłria, nĂŁo apenas consumidor de alheias. Verá a angĂşstia como deflagradora de criatividade, impulso Ă superação de limites. Como a literatura perde espaço na sociedade, torna-se esotĂ©rica, recomendamos seu abandono, em nome de outras narrativas que ensinarĂŁo a sociedade como trançado de discursos. Sensibilizado e consciente disto, o aluno entĂŁo pode trabalhar o literário como relação especial entre os discursos sociais
Minimizing plasma temperature for antimatter mixing experiments
The ASACUSA collaboration produces a beam of antihydrogen atoms by mixing pure positron and antiproton plasmas in a strong magnetic field with a double
cusp geometry. The positrons cool via cyclotron radiation inside the cryogenic trap. Low positron temperature is essential for increasing the fraction of antihydrogen atoms which reach the ground state prior to exiting the trap. Many experimental groups observe that such plasmas reach equilibrium at a temperature well above the temperature of the surrounding electrodes. This problem is typically attributed to electronic noise and plasma expansion, which heat the plasma. The present work reports anomalous heating far beyond what can be attributed to those two sources. The heating seems to be a result of the axially open trap geometry, which couples the plasma to the external (300 K) environment via microwave radiation
Upgrade of the positron system of the ASACUSA-Cusp experiment
The ASACUSA-Cusp collaboration has recently upgraded the positron system to
improve the production of antihydrogen. Previously, the experiment suffered
from contamination of the vacuum in the antihydrogen production trap due to the
transfer of positrons from the high pressure region of a buffer gas trap. This
contamination reduced the lifetime of antiprotons. By adding a new positron
accumulator and therefore decreasing the number of transfer cycles, the
contamination of the vacuum has been reduced. Further to this, a new rare gas
moderator and buffer gas trap, previously used at the Aarhus University, were
installed. Measurements from Aarhus suggested that the number of positrons
could be increased by a factor of four in comparison to the old system used at
CERN. This would mean a reduction of the time needed for accumulating a
sufficient number of positrons (of the order of a few million) for an
antihydrogen production cycle. Initial tests have shown that the new system
yields a comparable number of positrons to the old system.Comment: 10 pages, 5 figures, under consideration for the Special Collection
"Non-Neutral Plasmas: Achievements and Perspectives" in JP
Targeting Class A and C Serine \u3b2-Lactamases with a Broad-Spectrum Boronic Acid Derivative
Production of \u3b2-lactamases (BLs) is the most widespread resistance mechanism adopted by bacteria to fight \u3b2-lactam antibiotics. The substrate spectrum of BLs has become increasingly broad, posing a serious health problem. Thus, there is an urgent need for novel BL inhibitors. Boronic acid transition-state analogues are able to reverse the resistance conferred by class A and C BLs. We describe a boronic acid analogue possessing interesting and potent broad-spectrum activity vs class A and C serine-based BLs. Starting from benzo(b)thiophene-2-boronic acid (BZBTH2B), a nanomolar non-\u3b2-lactam inhibitor of AmpC that can potentiate the activity of a third-generation cephalosporin against AmpC-producing resistant bacteria, we designed a novel broad-spectrum nanomolar inhibitor of class A and C BLs. Structure-based drug design (SBDD), synthesis, enzymology data, and X-ray crystallography results are discussed. We clarified the inhibitor binding geometry responsible for broad-spectrum activity vs serine-active BLs using double mutant thermodynamic cycle studies
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