Universal mathematical model of power three-phase transformers and autotransformers

The substantiation of necessity in essential increase of completeness and reliability of modeling processes in energy systems has been shown. The results of synthesis of universal mathematical model of one of the main elements of energy systems - power transformers and autotransformers are given. The demanded quality of reproduction of processes is confirmed by experience of using the developed model in structure of all-mode multiprocessing modeling complexes of real time of the hybrid type. The examples illustrating quality of process modeling are shown

Exchange Coupling in GdM Compounds

The magnetic susceptibility of ferromagnetic GdM alloys (M=Cu$\text{}_{1-x}$Ga$\text{}_{x}$, Mg, Zn) has been investigated under helium gas pressure for temperatures above T$\text{}_{C}$. The evaluated pressure derivatives of the paramagnetic Curie temperature, dlnΘ/dP, appeared to be remarkably different for isovalent GdMg and GdZn compounds (-11.2 and -0.1 Mbar$\text{}^{-1}$, respectively). An analysis of the obtained dlnΘ/dP values for GdCu$\text{}_{1-x}$Ga$\text{}_{x}$ alloys and results of ab initio electronic structure calculations have revealed the essential role of 5d electrons as the mediators of exchange coupling in ferromagnetic GdM compounds. The pressure derivatives of T$\text{}_{C}$ were calculated by employing the modern mean-field theory, as well as the spin-fluctuation model. As a result, good agreement is found with the experimental values of dlnΘ/dP

Pressure Effect on Magnetic Properties of UGa3\text{}_{3}

The magnetic susceptibility, χ, of the itinerant antiferromagnetic compound UGa$\text{}_{3}$ was studied under pressure up to 2 kbar in the temperature range 64-300 K. The measured pressure derivative of the Néel temperature is found to be dT$\text{}_{N}$/dP=-1.1 K/kbar. In order to analyze the experimental magnetovolume effect values, d lnχ/d lnV, the volume dependent electronic structure of UGa$\text{}_{3}$ has been calculated ab initio in a paramagnetic phase by employing a relativistic full-potential linear muffin tin orbital method and including an external magnetic field self-consistently. The calculations revealed a predominance of itinerant uranium f-states at the Fermi energy, as well as a large orbital contribution to χ

Fluorescence Probing of Thiol-Functionalized Gold Nanoparticles: Is Alkylthiol Coating of a Nanoparticle as Hydrophobic as Expected?

Understanding the interaction of fluorescent dyes with monolayer-protected gold nanoparticles (AuNPs) is of fundamental importance in designing new fluorescent nanomaterials. Among a variety of molecular sensors and reporters, fluorescent probes based on a 3-hydroxychromone (3HC) skeleton appear to be very promising. They exhibit the phenomenon of dual band emission, resulting from excited-state intramolecular proton transfer (ESIPT), known to be highly sensitive to a nature of microenvironment surrounding a fluorophore. In this study, dodecanethiol-protected gold nanoparticles were synthesized, and, owing to the transmission electron micrograph imaging, their average diameter was found to be ∼1.4 nm. Fluorescence titrations of the 3HC ESIPT probes with AuNPs in toluene solutions demonstrate significant changes in the intensity ratio of their normal and tautomeric emission bands, suggesting that the probe molecules become noncovalently bound to a dodecanethiol layer of AuNPs. Despite expected fluorescence quenching induced by close proximity to the metal surface, no fluorescence lifetime decrease was observed, indicating that a bound-fluorophore is shielded from a nanoparticle core. Further spectral analysis revealed that the ratiometric fluorescence changes could be interpreted as a consequence of intermolecular hydrogen bonding between a probe and residual ethanol molecules, trapped into the dodecanethiol shell of AuNPs during the synthesis. Evidences for residual traces of ethanol in the ligand shell of the nanoparticles were also observed in NMR spectra, suggesting that alkylthiol-coated gold nanoparticles may not be as hydrophobic as one could expect. To elucidate structural features of dodecanethiol-stabilized gold nanoparticles at the supramolecular level, a molecular dynamics (MD) model of AuNP was developed. The model was based on the all-atom CHARMM27 force field parameters and parametrized according to available experimental data of the synthesized AuNPs. Our MD simulations show that in bulk toluene the 3HC probe molecule becomes weakly bound to a dodecanethiol monolayer, so that a fluorophore favors residence in an outer shell of AuNP. In addition, MD simulations of transfer of AuNP from bulk ethanol to toluene demonstrate that a small population of ethanol molecules are able to penetrate deeply into the dodecanethiol layer and may indeed be trapped into the ligand shell of alkylthiol-functionalized gold nanoparticles. The results of our fluorescence experiments and molecular dynamics simulation suggest that 3-hydroxychromones can be used as a noncovalent fluorescent labeling agent for alkylthiol-stabilized noble metal nanoparticles

Fluorescence Probing of Thiol-Functionalized Gold Nanoparticles: Is Alkylthiol Coating of a Nanoparticle as Hydrophobic as Expected?

Understanding the interaction of fluorescent dyes with monolayer-protected gold nanoparticles (AuNPs) is of fundamental importance in designing new fluorescent nanomaterials. Among a variety of molecular sensors and reporters, fluorescent probes based on a 3-hydroxychromone (3HC) skeleton appear to be very promising. They exhibit the phenomenon of dual band emission, resulting from excited-state intramolecular proton transfer (ESIPT), known to be highly sensitive to a nature of microenvironment surrounding a fluorophore. In this study, dodecanethiol-protected gold nanoparticles were synthesized, and, owing to the transmission electron micrograph imaging, their average diameter was found to be ∼1.4 nm. Fluorescence titrations of the 3HC ESIPT probes with AuNPs in toluene solutions demonstrate significant changes in the intensity ratio of their normal and tautomeric emission bands, suggesting that the probe molecules become noncovalently bound to a dodecanethiol layer of AuNPs. Despite expected fluorescence quenching induced by close proximity to the metal surface, no fluorescence lifetime decrease was observed, indicating that a bound-fluorophore is shielded from a nanoparticle core. Further spectral analysis revealed that the ratiometric fluorescence changes could be interpreted as a consequence of intermolecular hydrogen bonding between a probe and residual ethanol molecules, trapped into the dodecanethiol shell of AuNPs during the synthesis. Evidences for residual traces of ethanol in the ligand shell of the nanoparticles were also observed in NMR spectra, suggesting that alkylthiol-coated gold nanoparticles may not be as hydrophobic as one could expect. To elucidate structural features of dodecanethiol-stabilized gold nanoparticles at the supramolecular level, a molecular dynamics (MD) model of AuNP was developed. The model was based on the all-atom CHARMM27 force field parameters and parametrized according to available experimental data of the synthesized AuNPs. Our MD simulations show that in bulk toluene the 3HC probe molecule becomes weakly bound to a dodecanethiol monolayer, so that a fluorophore favors residence in an outer shell of AuNP. In addition, MD simulations of transfer of AuNP from bulk ethanol to toluene demonstrate that a small population of ethanol molecules are able to penetrate deeply into the dodecanethiol layer and may indeed be trapped into the ligand shell of alkylthiol-functionalized gold nanoparticles. The results of our fluorescence experiments and molecular dynamics simulation suggest that 3-hydroxychromones can be used as a noncovalent fluorescent labeling agent for alkylthiol-stabilized noble metal nanoparticles