Search results for "Fig"
showing 10 items of 1359 documents
Anharmonic vibrational frequency calculations for solvated molecules in the B3LYP Kohn–Sham basis set limit
2012
Abstract The solvent dependence of harmonic and anharmonic vibrational wavenumbers of water, formaldehyde and formamide was studied using the B3LYP method. The results obtained with the hierarchy of Jensen's polarization-consistent basis sets were fitted with two-parameter formula toward the B3LYP Kohn–Sham complete basis set (CBS) limit. Anharmonic corrections have been obtained by a second order perturbation treatment (VPT2) and vibrational configuration interaction (VCI) method. The solvent environment was treated according to the self-consistent reaction field polarizable continuum model (SCRF PCM) approach.
Semiconducting Clathrates Meet Gas Hydrates: Xe24[Sn136]
2014
Semiconducting Group 14 clathrates are inorganic host–guest materials with a close structural relationship to gas hydrates. Here we utilize this inherent structural relationship to derive a new class of porous semiconductor materials: noble gas filled Group 14 clathrates (Ngx[M136], Ng=Ar, Kr, Xe and M=Si, Ge, Sn). We have carried out high-level quantum chemical studies using periodic Local-MP2 (LMP2) and dispersion-corrected density functional methods (DFT-B3LYP-D3) to properly describe the dispersive host–guest interactions. The adsorption of noble gas atoms within clathrate-II framework turned out to be energetically clearly favorable for several host–guest systems. For the energetically…
Recent advances in on-line solid-phase pre-concentration for inductively-coupled plasma techniques for determination of mineral elements
2012
Abstract We provide a critical survey on recent progress in on-line solid-phase pre-concentration for inductively-coupled plasma (ICP)-based techniques for trace-level determination of metals. We highlight some of the useful solid-phase materials suitable for on-line separation and enrichment prior to ICP determination. We discuss different applications of the methods developed along with their analytical figures of merit. Finally, we sketch out future prospects in this field.
Obraz Hrista v romane Čingiza Ajtmatova "Plaha"
2011
Aitmatov introduced a biblical motif into his novel – he chose Christ examination by Pilate. The writer extended the meaning of the scene, he altered its essence and “genre,” changing it into philosophical disputation. He also invented the story of Christ sailing with his mother on the Nile and their miraculous rescue by a crocodile. These scenes are presented in such a way that they remind the myth of the birth and death of Christ which allows rating Aitmatov's figure of Christ to the fifth category of literary embodiment of Christ proposed by T. Ziołkowski and called CHRIST AS A MYTH. A figure of Christ in the novel is a symbol of the highest perfection of humanity.
Fixed constructions in French and Chinese
2017
Languages are not just instruments of communication. Claude Hagège (2012: 181) reminds that all languages are rooted in a pool of knowledge, sensations, memories, images, dreams, which are the fabric of a speaker's competence. Languages are very complex and multidimensional phenomena. However, it is impossible to carry out a complete study of languages, without taking into account a generalized and pervasive phenomenon: the fixedness.In light of a great deal of progress which has been made by the research on phraseology, we realize that many gray areas still exist; indeed, some true mysteries remain to be unraveled. Contrastive studies have always helped to advance knowledge of language, es…
Wireless MAC processors: programming MAC protocols on commodity hardware
2012
Programmable wireless platforms aim at responding to the quest for wireless access flexibility and adaptability. This paper introduces the notion of wireless MAC processors. Instead of implementing a specific MAC protocol stack, Wireless MAC processors do support a set of Medium Access Control “commands” which can be run-time composed (programmed) through software-defined state machines, thus providing the desired MAC protocol operation. We clearly distinguish from related work in this area as, unlike other works which rely on dedicated DSPs or programmable hardware platforms, we experimentally prove the feasibility of the wireless MAC processor concept over ultra-cheap commodity WLAN hardw…
Total Synthesis of (±)-Oxalicumone C and Chiral Resolution and Elucidation of Its Absolute Configuration
2014
The racemic total synthesis, the chiral resolution, and the elucidation of the absolute configuration of the natural product oxalicumone C were investigated. The goal was achieved by a synthetic strategy beginning with the synthesis of a 5-hydroxy-7-methylchromone precursor. Further modification possibilities were achieved by introduction of a vinyl moiety into the chromone, which was based on a selective iodination step in the 3-position. Further transformations furnished the racemic natural product. To determinate the absolute configuration of naturally occurring oxalicumone C, both enantiomers were separated by chiral HPLC. Comparison of the calculated and experimental vibrational circul…
Labdane Diterpenes from Stachys plumosa
2000
Three new labdane diterpenoids were isolated from the aerial parts of Stachys plumosa. The first two (1, 2) were the dextrorotatory enantiomers of the known 6-deoxyandalusol and 13-epijabugodiol. Structures were determined using NMR and MS techniques. The absolute stereochemistry of the third compound (3) was not experimentally proved.
Peak deconvolution in one-dimensional chromatography using a two-way data approach.
2002
A deconvolution methodology for overlapped chromatographic signals is proposed. Several single-wavelength chromatograms of binary mixtures, obtained in different runs at diverse concentration ratios of the individual components, were simultaneously processed (multi-batch approach), after being arranged as two-way data. The chromatograms were modelled as linear combinations of forced peak profiles according to a polynomially modified Gaussian equation. The fitting was performed with a previously reported hybrid genetic algorithm with local search, leaving all model parameters free. The approach yielded more accurate solutions than those found when each experimental chromatogram was fitted in…
Flavans and other chemical constituents of Crinum biflorum (Amaryllidaceae)
2019
Abstract The ethyl acetate extract from the whole plant of Crinum biflorum Rottb. Showed a moderate activity against Enterococcus faecalis. Its phytochemical investigation led to the isolation of a new flavan-3-ol derivative namely (2R,3R)-3-hydroxy-7-methoxy-3′,4′-methylenedioxyflavan, together with (2S)-7-hydroxy-3′,4′-methylenedioxyflavan, (2R,3R)-7-methoxy-flavan-3-ol, (2S)-7-hydroxy-3′,4′-dimethoxyflavan, 3′,7-dihydroxy-4′-methoxyflavan, 4′,7-dimethoxy-3′-hydroxyflavan, farrerol, β-sitosterol, β-sitosterol-3-O-β-D-glucopyranoside, oleanolic acid, kaempferol, pancratistatin, lupeol, aurantiamide acetate, Narciprimine and 2,3-dihydroxypropyl palmitate. Their structures were elucidated ma…