Search results for "Meri"
showing 10 items of 7596 documents
Controlled radical polymerization of alkyl acrylates and styrene using a half-sandwich molybdenum(III) complex containing diazadiene ligands
2003
Abstract The half-sandwich molybdenum(III) complex CpMoCl 2 ( i Pr 2 -dad) ( i Pr 2 -dad= i Pr–NCH–CHN– i Pr) proved to be an effective metal catalyst for the controlled radical polymerization of methyl acrylate, butyl acrylate, and styrene. In conjunction with an alkyl iodide [R–I: CH 3 CH(COOEt)I] as an initiator and in the presence or absence of Al(O– i -Pr) 3 as a co-catalyst, the molybdenum-based system gave polymers with narrow molecular weight distributions. The in situ addition of styrene to a macroinitiator of poly(methylacrylate) afforded an AB-type block copolymer.
Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents
2014
Palladium-catalysed cross-coupling of secondary C(sp(3)) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation with organolithium reagents, herein we present a Pd-catalysed cross-coupling of secondary alkyllithium reagents with aryl and alkenyl bromides. The reaction proceeds at room temperature and on short timescales with high selectivity and yields. This methodology is also applicable to hindered aryl bromides, which are a major challenge in the field of metal catalysed cross-coupling reactions.
Spontaneous quantity discrimination of artificial flowers by foraging honeybees
2020
ABSTRACTMany animals need to process numerical and quantity information in order to survive. Spontaneous quantity discrimination allows differentiation between two or more quantities without reinforcement or prior training on any numerical task. It is useful for assessing food resources, aggressive interactions, predator avoidance and prey choice. Honeybees have previously demonstrated landmark counting, quantity matching, use of numerical rules, quantity discrimination and arithmetic, but have not been tested for spontaneous quantity discrimination. In bees, spontaneous quantity discrimination could be useful when assessing the quantity of flowers available in a patch and thus maximizing f…
Controlled time integration for the numerical simulation of meteor radar reflections
2016
We model meteoroids entering the Earth[U+05F3]s atmosphere as objects surrounded by non-magnetized plasma, and consider efficient numerical simulation of radar reflections from meteors in the time domain. Instead of the widely used finite difference time domain method (FDTD), we use more generalized finite differences by applying the discrete exterior calculus (DEC) and non-uniform leapfrog-style time discretization. The computational domain is presented by convex polyhedral elements. The convergence of the time integration is accelerated by the exact controllability method. The numerical experiments show that our code is efficiently parallelized. The DEC approach is compared to the volume …
Narkotiku nozīme Alena Ginsberga dzejolī "Kauciens" (1956)
2022
Šis darbs ir vērsts uz narkotiku nozīmes izpēti Alena Ginsberga dzejolī "Kauciens "(1956), kā arī Beat Paaudzi un narkotiku vēsturi Amerikas pēckara sabiedrībā un metaforu izmantošanu simbolikas literatūrā. Šī darba mērķis ir rūpīgi izpētīt teoriju par metaforām, kā arī teoriju par simboliku un izmantot šo teoriju, lai iegūtu metaforas, ko izmanto, lai runātu par narkotikām Alena Ginsberga dzejā, noteiktu šo metaforu nozīmi un izdarītu secinājumus. Analīze ir parādījusi, ka narkotikas "Kauciens" (1956) ir metafora augstākam redzējumam, apgaismotai realitātei, kuru cilvēks var sasniegt, lietojot vielas. Dzejolis parāda pilnu ceļojumu no pirmās narkotiku ekstazī līdz izmisīgajai vajadzībai pē…
Inchieste sociali e subalternità. Dal concetto gramsciano di "subalterno" alle storie di vita di Scotellaro e Montaldi. Rappresentazione e intervento…
2014
Una aproximación a la biblioteca del ilustrado valenciano Juan Bautista Muñoz (1745-1799)
1998
El presente estudio sobre la biblioteca del ilustrado valenciana Juan Bautista Muñoz (1745-1799) muestra las preocupaciones intelectuales que marcaron su trayectoria intelectual. Impulsor de la filosofía moderna en la Universidad de Valencia, fundador del Archivo General de Indias y autor de la Historia del Nuevo Mundo (1793), poseía una selecta y voluminosa biblioteca que contenía los libros más vanguardistas en las diversas disciplinas (filosofía, historia de América, religión, literatura, ciencias). Su biblioteca es paradigma de un hombre preocupado por integrar en su sociedad los valores de modernidad que circulaban por Europa.
Hyperbranched polyethylenimines as versatile precursors for the preparation of different type of unimolecular micelles
2007
Abstract Hyperbranched polyethylenimine (HPEI) was successfully employed as precursor for the preparation of unimolecular inverted and aqueous micelles. The unimolecular inverted micelles (UIMs) obtained by the amidation of HPEI with 1,1′-carbonyldiimidazole (CDI) activated palmitic acid exhibited high encapsulation efficiency for hydrophilic anionic dyes and the efficiency could be enhanced significantly by decreasing the degree of amidation or quaternizing the residual amines. The weight ratio of loaded guests to the amidated HPEIs was not dependent on the molecular weight of HPEI core when the degree of amidation was kept constant. Decreasing the length of the aliphatic chain from 16 to …
Resolution enhancement in quantitative phase microscopy
2019
Quantitative phase microscopy (QPM), a technique combining phase imaging and microscopy, enables visualization of the 3D topography in reflective samples, as well as the inner structure or refractive index distribution of transparent and translucent samples. Similar to other imaging modalities, QPM is constrained by the conflict between numerical aperture (NA) and field of view (FOV): an imaging system with a low NA has to be employed to maintain a large FOV. This fact severely limits the resolution in QPM up to 0.82λ/NA, λ being the illumination wavelength. Consequently, finer structures of samples cannot be resolved by using modest NA objectives in QPM. Aimed to that, many approaches, suc…
Synthesis, reactions and structural features of monofluorinated cyclopropanecarboxylates
2002
Abstract Monofluorinated cyclopropanecarboxylates are available in racemic or optically active form by transition metal-catalyzed reactions of vinylfluorides with diazoacetates. From α-fluorostyrene and tert-butyl diazoacetate in the presence of 2 mol% of an enantiopure bis(oxazoline) copper complex, a 81:19 mixture of tert-butyl trans- and cis-2-fluoro-2-phenylcyclopropanecarboxylates was obtained with high enantiomeric excess (ee) of 93 or 89%, respectively. The corresponding racemic ethylesters were used as starting materials for the synthesis of carboxamides, of the cis- and trans-isomers of analogues of tranylcypromine, an anti-depressive drug and several of its homologous fluorinated …