Search results for "16"
showing 10 items of 8074 documents
Structural and electronic elucidation of a N-heterocyclic silylene vanadocene adduct
2017
The solid and solution state structure of the vanadium(II) N‐ heterocyclic silylene (NHSi) complex, [(SiIPr)V(Cp)2] (1) is reported ( SiIPr: 1,3‐bis(2,6‐diisopropylphenyl)‐1,3‐diaza‐2‐silacyclopent‐4‐ en‐2‐ylidene). The electronic structure of 1 is probed using combination of magnetic measurements, EPR spectroscopy and computational studies. The V–Si bond strength and complex forming mechanism between vanadocene and NHSi ligand is elucidated using computational methods. peerReviewed
Skolotāja vecuma loma skolēnu sasniegumos starptautiskajā skolēnu pilsoniskās izglītības pētījumā: Latvijas piemērs IEA ICCS 2016
2018
Maģistra darba mērķis ir, pamatojoties uz zinātniskās literatūras izpēti un darba autores veikto starptautiskā pilsoniskās izglītības pētījuma IEA ICCS 2016 skolotāju aptaujas datu analīzi, noskaidrot skolotāju vecuma ietekmi uz skolēnu uzrādītajiem rezultātiem pilsoniskajā izglītībā. Pētnieciskā darba rezultātā tiek sniegta atbilde uz izvirzīto pētniecisko jautājumu - kāda ir skolotāju vecuma ietekme uz Latvijas skolēnu pilsoniskās izglītības sasniegumiem? Ir vērojama statistiski nozīmīga skolotāju vecuma negatīva ietekme uz skolēnu uzrādītajiem rezultātiem pilsoniskajā izglītībā, bet ar skolēnu sasniegumiem korelējošo aptaujas jautājumu atbilžu rādītājos tā tika konstatēta tikai vienā jau…
Plasma-wall interaction studies within the EUROfusion consortium: Progress on plasma-facing components development and qualification
2017
This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014-2018 under grant agreement No 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission.
Kohn-Sham Decomposition in Real-Time Time-Dependent Density-Functional Theory An Efficient Tool for Analyzing Plasmonic Excitations
2017
The real-time-propagation formulation of time-dependent density-functional theory (RT-TDDFT) is an efficient method for modeling the optical response of molecules and nanoparticles. Compared to the widely adopted linear-response TDDFT approaches based on, e.g., the Casida equations, RT-TDDFT appears, however, lacking efficient analysis methods. This applies in particular to a decomposition of the response in the basis of the underlying single-electron states. In this work, we overcome this limitation by developing an analysis method for obtaining the Kohn-Sham electron-hole decomposition in RT-TDDFT. We demonstrate the equivalence between the developed method and the Casida approach by a be…
Fracture and fatigue of titanium narrow dental implants: New trends in order to improve the mechanical response
2019
Sixty-four fractured commercially pure titanium (cp-Ti) narrow dental implants (NDIs) with similar macrogeometry and connection designs were studied after different implantation times in humans in order to determine their reliability and to evaluate the causes of the fracture. These NDIs were compared with other similar implants, made with alloyed titanium with 15% Zr and with 12% strained titanium. Original implants were tested under static and fatigue conditions, simulating the tri-axial loads in the mouth by means of a Bionix hydraulic test machine. Fractography was studied using field-emission scanning electron microscopy (FSEM). The results showed that cp-Ti NDI exhibits low strength f…
Self-Consistent Charge Density-Functional Tight-Binding Parametrization for Pt–Ru Alloys
2017
We present a self-consistent charge density-functional tight-binding (SCC-DFTB) parametrization for PtRu alloys, which is developed by employing a training set of alloy cluster energies and forces obtained from Kohn-Sham density-functional theory (DFT) calculations. Extensive simulations of a testing set of PtRu alloy nanoclusters show that this SCC-DFTB scheme is capable of capturing cluster formation energies with high accuracy relative to DFT calculations. The new SCC-DFTB parametrization is employed within a genetic algorithm to search for global minima of PtRu clusters in the range of 13-81 atoms and the emergence of Ru-core/Pt-shell structures at intermediate alloy compositions, consi…
PtII versus PdII-assisted [2+3] cycloadditions of nitriles and nitrone. Synthesis of nitrile-derived arylamido platinum(II) and Δ4-1,2,4-oxadiazoline…
2019
Abstract The reactions of bis(organonitrile) platinum(II) complexes trans-[PtCl2(N CR)2] (R = C6H4(p-HC O), CH2C6H4(p-CH3)) with pyrroline N-oxide −O+N CHCH2CH2CMe2 afford arylamido platinum(II) complexes trans-[PtCl2{(O CR)N CCH2CH2CMe2NH}2] (R = C6H4(p-HC O) (1), CH2C6H4(p-CH3) (2)). The spectral data of 1 and 2 show that the oxadiazoline rings in both cases have opened by a spontaneous N O bond cleavage to form (Z)-p-formyl-N-(5,5-dimethylpyrrolidin-2-ylidene)benzamide or (Z)-N-(5,5-dimethylpyrrolidin-2-ylidene)-2-p-tolylacetamide ligands, respectively, where the N-atoms of the benzamide or acetamide moieties coordinate to platinum(II) metal centre in trans positions. However, the reacti…
Bis(hydroxyammonium) hexachloridoplatinate(IV)–18-crown-6 (1/2)
2014
In the title complex, (NH3OH)2[PtCl6]·2C12H24O6, the PtIV atom is coordinated by six chloride anions in a slightly distorted octahedral geometry. The Pt—Cl bond lengths are comparable to those reported for other hexachloridoplatinate(IV) species. The hydroxyammonium groups act as linkers between the [PtCl6]2− anion and the crown ether molecules. The anion is linked to two hydroxyammonium cations via O—H...Cl hydrogen bonds and each hydroxyammonium moiety is linked to a crown ether molecule by hydrogen bonds between ammonium H atoms and 18-crown-6 O atoms. The crown ether molecules have the classic crown shape in which all O atoms are located in the inner part of the crown ether ring and all…
Non-conventional synthesis and photophysical studies of platinum(ii) complexes with methylene bridged 2,2′-dipyridylamine derivatives
2019
Methylene bridged 2,2′-dipyridylamine (dpa) derivatives and their metal complexes possess outstanding properties due to their inherent structural flexibility. Synthesis of such complexes typically involves derivatization of dpa followed by coordination on metals, and may not always be very efficient. In this work, an alternative synthetic approach, involving the derivatization step after – rather than prior to – coordination of dpa on metal center, is proposed and applied to synthesis of a number of platinum(II) complexes with substituted benzyldi(2-pyridyl)amines. Comparison with the more conventional synthetic route reveals greater efficiency and versatility of the proposed approach. The …