Search results for "Taut"
showing 10 items of 916 documents
Starptautisko pārrunu procesa nozīme konfliktu risināšanā: Minskas Vienošanās un Minska II
2018
Šī bakalaura darba mērķis ir identificēt stratēģijas un taktikas noteiktā starptautisko pārrunu procesa posmā, lai piemērotu to analīzi abu Minskas līgumu pārrunu procesam. Tādā veidā noskaidrot, kā atbilstoša teorētiskā modeļa izmantošana var ietekmēt miera līguma rezultātus un tā ieviešanu, lai nodrošinātu mieru un atrisinātu konfliktu. Darba teorētiskajā ietvarā tiek analizēta starptautisko pārrunu koncepta attīstība un galvenās koncepta definīcijas, lai attiecīgi izstrādātu teorētisko pārrunu četru posmu modeli. Par darba teorētisko pamatu galvenokārt tiek izmantoti Annas Duglasas, Lindas Patnemas, Pītera Valenstīna, Viljama Zartamana, Daniela Drukmana, Džona Odela un Roja Levicki darbi…
Reaction between Indazole and Pd-Bound Isocyanides-A Theoretical Mechanistic Study
2018
The mechanism of the addition of indazole (Ind)&mdash
Critical Role of Substrate Conformational Change in the Proton Transfer Process Catalyzed by 4-Oxalocrotonate Tautomerase
2009
4-Oxalocrotonate tautomerase enzyme (4-OT) catalyzes the isomerization of 2-oxo-4-hexenedioate to 2-oxo-3-hexenedioate. The chemical process involves two proton transfers, one from a carbon of the substrate to the nitrogen of Pro1 and another from this nitrogen atom to a different carbon of the substrate. In this paper the isomerization has been studied using the combined quantum mechanical and molecular mechanical (QM/MM) method with a dual-level treatment of the quantum subsystem employing the MPW1BK density functional as the higher level. Exploration of the potential energy surface shows that the process is stepwise, with a stable intermediate state corresponding to the deprotonated subs…
Stereoelectronic Requirements for Optimal Hydrogen-Bond-Catalyzed Enolization
2011
Protein crystallographic analysis of the active sites of enolizing enzymes and structural analysis of hydrogen-bonded carbonyl compounds in small molecule crystal structures, complemented by quantum chemical calculations on related model enolization reactions, suggest a new stereoelectronic model that accounts for the observed out-of-plane orientation of hydrogen-bond donors (HBDs) in the oxyanion holes of enolizing enzymes. The computational results reveal that the lone-pair directionality of HBDs characteristic for hydrogen-bonded carbonyls is reduced upon enolization, and the enolate displays almost no directional preference for hydrogen bonding. Positioning the HBDs perpendicular to the…
Factors Governing the Chemical Stability and NMR Parameters of Uracil Tautomers and Its 5-Halogen Derivatives
2020
We report on the density functional theory (DFT) modelling of structural, energetic and NMR parameters of uracil and its derivatives (5-halogenouracil (5XU), X = F, Cl, Br and I) in vacuum and in water using the polarizable continuum model (PCM) and the solvent model density (SMD) approach. On the basis of the obtained results, we conclude that the intramolecular electrostatic interactions are the main factors governing the stability of the six tautomeric forms of uracil and 5XU. Two indices of aromaticity, the harmonic oscillator model of aromaticity (HOMA), satisfying the geometric criterion, and the nuclear independent chemical shift (NICS), were applied to evaluate the aromaticity of ur…
Equilibrium, Kinetic, and Computational Studies on the Formation of Cu2+ and Zn2+ Complexes with an Indazole-Containing Azamacrocyclic Scorpiand: Evi…
2015
Cu(2+) and Zn(2+) coordination chemistry of a new member of the family of scorpiand-like macrocyclic ligands derived from tris(2-aminoethyl)amine (tren) is reported. The new ligand (L1) contains in its pendant arm not only the amine group derived from tren but also a 6-indazole ring. Potentiometric studies allow the determination of four protonation constants. UV-vis and fluorescence data support that the last protonation step occurs on the indazole group. Equilibrium measurements in the presence of Cu(2+) and Zn(2+) reveal the formation of stable [ML1](2+), [MHL1](3+), and [ML1(OH)](+) complexes. Kinetic studies on the acid-promoted decomposition of the metal complexes were carried out usi…
Annular Tautomerism of 3(5)-Disubstituted-1H-pyrazoles with Ester and Amide Groups
2019
A series of disubstituted 1H-pyrazoles with methyl (1), amino (2), and nitro (3) groups, as well as ester (a) or amide (b) groups in positions 3 and 5 was synthesized, and annular tautomerism was investigated using X-ray, theoretical calculations, NMR, and FT-IR methods. The X-ray experiment in the crystal state showed for the compounds with methyl (1a, 1b) and amino (2b) groups the tautomer with ester or amide groups at position 3 (tautomer 3), but for those with a nitro group (3b, 4), tautomer 5. Similar results were obtained in solution by NMR NOE experiments in CDCl3, DMSO-d6, and CD3OD solvents. However, tautomer equilibrium was observed for 2b in DMSO. The FT-IR spectra in chloroform …
Biomimetic Synthesis of the Apoptosis-Inducing Thiazinoquinone Thiaplidiaquinone A
2012
A concise total synthesis of the apoptosis-inducing, marine metabolite thiaplidiaquinone A is described. The key ring forming steps are both based on biosynthetic considerations and involve the construction of the central benzo[c]chromene quinone unit by an extremely facile oxa-6π-electrocyclic ring closure reaction of an ortho-quinone intermediate, derived by tautomerization of a bis-benzoquinone, readily accessed from two simple phenolic precursors. This is followed by the installation of the 1,4-thiazine-dioxide ring by reaction of the benzo[c]chromene quinone with hypotaurine.
Skolotāju pedagoģiskās darbības salīdzinoša analīze latviešu un mazākumtautību sākumskolu klasēs: sociālā pedagoģija
2006
Latviešu tautas rakstu izmantošana reklāmā
2019
Bakalaura darbā tiek pētīti jautājumi par kultūrvērtību un datorprogrammām, ar kurām ērtāk un veiksmīgāk veidot jaunus ornamentus un rakstus, izvērtēti pirmie latviešu tautas rakstu un ornamentu pētnieki un viņu devums etnogrāfijas nozarē, veikta aptauja, lai noskaidrotu populārākos un atpazīstamākos latviešu tautas rakstus, noskaidrots, kā latviešu tautas raksti tiek izmantoti reklāmā. Radošais darbs – Bērnu deju ansambļa “Dzīpariņš” 25 gadu jubilejas koncerta afiša, buklets un scenogrāfija. Rezultātā iegūtas atziņas, ka latviešu tautai ir savi tautas raksti, latvju zīmes, kas norāda uz piederību šai valstij, ka vispopulārākās un atpazīstamākās zīmes ir Jumis, Auseklis un Saules zīme, ka l…