Test results of the prototype for frequency step tunable 105-170 GHz lMW Gyrotro

The report presents results of investigation of the possibility to optimise numerically and experimentally helical electron beam formation system and processes of mode interaction in the electron beam-cavity system for the prototype of 105-170 GHz 1 MW step tunable gyrotron with different operating mode. Parameters are optimized to achieve maximum efficiency of the gyrotron with an acceptable Ohmic load on the cavity. The influence of mode competition, electron beam potential depression and beam energy recovery is investigated also. Possibility to optimize mode converter system for dif;.ferent operating modes is discussed.conference pape

Conformations of certain ethylene ketals with vicinal C-Hal bonds

The g⇌t equilibrium is displaced toward the less polar gauche form in the ethylene ketals of 2-chlorocyclohexanone and 2-bromocyclohexanone, and in the chloro- and bromoacetaldehydes. © 1978 Plenum Publishing Corporation

Metabolic Pathway of Topramezone in Multiple-Resistant Waterhemp (Amaranthus tuberculatus) Differs From Naturally Tolerant Maize

Waterhemp [Amaranthus tuberculatus (Moq.) Sauer] is a problematic dicot weed in maize, soybean, and cotton production in the United States. Waterhemp has evolved resistance to several commercial herbicides that inhibit the 4-hydroxyphenylpyruvate-dioxygenase (HPPD) enzyme in sensitive dicots, and research to date has shown that HPPD-inhibitor resistance is conferred by rapid oxidative metabolism of the parent compound in resistant populations. Mesotrione and tembotrione (both triketones) have been used exclusively to study HPPD-inhibitor resistance mechanisms in waterhemp and a related species, A. palmeri (S. Wats.), but the commercial HPPD inhibitor topramezone (a pyrazolone) has not been investigated from a mechanistic standpoint despite numerous reports of cross-resistance in the field and greenhouse. The first objective of our research was to determine if two multiple herbicide-resistant (MHR) waterhemp populations (named NEB and SIR) metabolize topramezone more rapidly than two HPPD inhibitor-sensitive waterhemp populations (named SEN and ACR). Our second objective was to determine if initial topramezone metabolite(s) detected in MHR waterhemp are qualitatively different than those formed in maize. An excised leaf assay and whole-plant study investigated initial rates of topramezone metabolism (<24 h) and identified topramezone metabolites at 48 hours after treatment (HAT), respectively, in the four waterhemp populations and maize. Results indicated both MHR waterhemp populations metabolized more topramezone than the sensitive (SEN) population at 6 HAT, while only the SIR population metabolized more topramezone than SEN at 24 HAT. Maize metabolized more topramezone than any waterhemp population at each time point examined. LC-MS analysis of topramezone metabolites at 48 HAT showed maize primarily formed desmethyl and benzoic acid metabolites, as expected based on published reports, whereas SIR formed two putative hydroxylated metabolites. Subsequent LC-MS/MS analyses identified both hydroxytopramezone metabolites in SIR as different hydroxylation products of the isoxazole ring, which were also present in maize 48 HAT but at very low levels. These results indicate that SIR initially metabolizes and detoxifies topramezone in a different manner than tolerant maize

The powerful microwave sources for materials processing

At present, gyrotron systems are finding increasing use in research into processing of materials with the millimeter-wave energy. A 3.5 kW, 24 GHz compact gyrotron system for laboratory research with extended functional capabilities has been developed. The design of the transmission lines features high efficiency and prevents influence of the radiation reflected from an applicator on the gyrotron operation. The applicator is designed for both volumetric heating of materials and surface treatment by a focused wave beam. The manual and automatic modes of PC-based control of the microwave processing are available. Experiments performed up to the present have demonstrated the multifunctional operating capabilities of the system. The efficiency of 50% at a 24-30 GHz 10-30 kW CW power level was obtained in gyrotrons operated on fundamental and second harmonics of electron cyclotron resonance. Frequency-broadband gyro-BWO are currently under development. In the experiment was obtained a pulse output power about 5 kW with smooth frequency tuning within a frequency range of 23.5-25 GHz.conference pape

Insertion of Isocyanides into N-Si Bonds: Multicomponent Reactions with Azines Leading to Potent Antiparasitic Compounds.

Trimethylsilyl chloride is an efficient activating agent for azines in isocyanide-based reactions, which then proceed through a key insertion of the isocyanide into a N-Si bond. The reaction is initiated by N activation of the azine, followed by nucleophilic attack of an isocyanide in a Reissert-type process. Finally, a second equivalent of the same or a different isocyanide inserts into the N-Si bond leading to the final adduct. The use of distinct nucleophiles leads to a variety of α-substituted dihydroazines after a selective cascade process. Based on computational studies, a mechanistic hypothesis for the course of these reactions was proposed. The resulting products exhibit significant activity against Trypanosoma brucei and T. cruzi, featuring favorable drug-like properties and safety profiles

Conversion of Isatins to Tryptanthrins, Heterocycles Endowed with a Myriad of Bioactivities

International audienceThe numerous bioactivities exhibited by tryptanthrins led chemists to develop synthetic approaches towards this important scaffold. In particular, conversion of isatins into tryptanthrins has been the subject of several studies. In this context, by using iodine and potassium hydroxide at room temperature, we have discovered a simple way to convert isatin and seven of its 5-substituted derivatives (Bu, F, Cl, Br, I, OMe and OCF 3 ) into the corresponding tryptanthrins. Furthermore, a mechanism was proposed to explain this original reactivity. Finally, we evaluated the antibacterial, antifungal, antioxidant and cytotoxic properties of the synthesized tryptanthrins. The unprecedented inhibition of human 20S constitutive proteasome was finally evaluated

Neue Synthesen stickstoffhaltiger Heterocyclen aus Isocyaniden

Die direkte kupfer(I)-katalysierte Synthese 2,3,4-trisubstituierter und 3,4-disubstituierter Pyrrole aus substituierten Methylisocyaniden und akzeptor-substituierten Acetylenen sowie ein neu gefundener Zugang zu 2,3-disubstituierten Pyrrolen aus substituierten Methylisocyaniden und nicht aktivierten Acetylenen wurden untersucht. 2-Substituierte Phenylisocyanide wurden bei Halogen-Lithium Austausch Reaktion des ortho-Bromphenylisocyanids und folgendem Abfangen des so gebildeten ortho-Lithiophenylisocyanides mit Elektrophilen hergestellt. Diese Strategie wurde für die neue dreistufige Eintopfsynthese substituierter 3H-Quinazolin-4-one (-thione) einschließlich der natürliche vorkommenden Alkaloide Deoxyvasicinon und Tryptanthrin effiktiv eingesetzt. Die Reaktionen von ortho-Lithiophenylisocyanid und anderen ortho-Lithiohetarylisocyaniden mit Aldehyden, Ketonen und Kohlenstoffdioxid ergaben außer erwarteten Isocyanoalkoholen, 4H-3,1-Benzoxazine, und 4H-Benzoxazin-4-one, Iminophthalanes bzw. Indolin-2-one bei zwei neuen Umlagerungen von intermediären 2-Lithio-4H-3,1-Benzoxazinen. Die neue kupfer-katalysierte Synthese von Benzimidazolen aus ortho-Bromoarylisocyaniden und primären Aminen wurde entwickelt. Diese neue sequenzielle Reaktion liefert einen bequemen Zugang zu 1-substituierten Benzimidazolen und ähnlichen 3-substituierten 3H-Thieno[2,3-d]imidazolen in mittleren bis zu guten Ausbeuten