Cyclometallated 1,2,3-triazol-5-ylidene iridium(III) complexes: synthesis,structure, and photoluminescence properties

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Neutron emission during a nanosecond discharge in deuterium in a nonuniform electric field

Neutron emission during a nanosecond deuterium discharge formed at the nonuniform electric field is investigated. A stable neutron yield is observed when the cathode is made of metallic plates covered by a layer of deuterated zirconium and the anode is made of stainless steel in the form of a tube. It is shown that, when the deuterium pressure equals several Torr, neutrons are emitted from both deuterated and deuterium-free cathodes. The influence of the anode design on the neutron yield is studied.     

Effect of thermal stresses on the phase transition temperature in a ferroelectric-dielectric nanocomposite

The mechanism of an increase in the phase transition temperature of a ferroelectric-dielectric nanocomposite above the corresponding temperature of an unbounded homogeneous ferroelectric has been revealed. The significant thermal stresses induced in the composite material due to the difference in the thermal and elastic characteristics of its components affect the polarized state of the ferroelectric component via the electrostrictive coupling and can lead to an increase in the phase transition temperature of the composite.     

On the possible mechanism of increase in the phase transition temperature in a ferroelectric-insulator composite

The phase transition temperature of a small ferroelectric sample has been determined by solving the system of nonlinear equations of electrostatics and the equilibrium equation with a nonlinear boundary condition at the sample surface with the use of a method of finite elements. It has been shown that the phase transition temperature can be shifted to higher temperatures owing to the effect of the surface. The dependence of the phase transition temperature on the size and shape of the ferroelectric sample and on the properties of its surface has been found. The possibility of the experimental observation of this effect has been discussed.     

The Concept of Folic Acid in Health and Disease

Folates have a pterine core structure and high metabolic activity due to their ability to accept electrons and react with O-, S-, N-, C-bounds. Folates play a role as cofactors in essential one-carbon pathways donating methyl-groups to choline phospholipids, creatine, epinephrine, DNA. Compounds similar to folates are ubiquitous and have been found in different animals, plants, and microorganisms. Folates enter the body from the diet and are also synthesized by intestinal bacteria with consequent adsorption from the colon. Three types of folate and antifolate cellular transporters have been found, differing in tissue localization, substrate affinity, type of transferring, and optimal pH for function. Laboratory criteria of folate deficiency are accepted by WHO. Severe folate deficiencies, manifesting in early life, are seen in hereditary folate malabsorption and cerebral folate deficiency. Acquired folate deficiency is quite common and is associated with poor diet and malabsorption, alcohol consumption, obesity, and kidney failure. Given the observational data that folates have a protective effect against neural tube defects, ischemic events, and cancer, food folic acid fortification was introduced in many countries. However, high physiological folate concentrations and folate overload may increase the risk of impaired brain development in embryogenesis and possess a growth advantage for precancerous altered cells.     

exo- and endo-Complexes of Fe(0) with Carbon Allotropic Modifications on the Example of Fullerene С60: a Density Function Theory Study

Russian Journal of General Chemistry - Structures of exo- and endo-complexes of fullerene C60 with zero-valent Fe0, in which the metal is localized inside and outside fullerene molecule,...     

Study of the pd reaction at ultralow energies using hydrogen liner plasma

The pd reaction (pd → He + γ (5.5 MeV)) is studied in the astrophysical energy collision range of protons with deuterons using the hydrogen liner in the inverse Z-pinch configuration at the pulsed power generator MIG (HCEI, Tomsk). Fundamental characteristics of this and other light-nucleus reactions at ultralow energies are important for problems of basic physics and astrophysics. The knowledge of the energy distribution of the nuclei participating in these reactions is important due to their exponential type of dependence on the collision energy. Two experimental techniques were designed and tested for recovering the energy distribution of liner protons incident on the CD₂ target by using optical detectors and ion collectors. It is shown that the combined use of these two techniques could provide relevant information on the energy distribution of the accelerated protons in the liner. The estimates of the upper limits for the astrophysical S factor and effective cross section of the pd reaction in the proton-deuteron collision energy range of 2.7–16.7 keV are obtained: $\bar S_{pd} (E_{pd} = 10.2 keV) \leqslant 2.5 \times 10^{ - 7} MeV b;\overline \sigma _{pd} (2.7 \leqslant E_{pd} \leqslant 16.7 keV) \leqslant 4 \times 10^{ - 33} cm^2 $ .     

Vibrational spectra and structural features of carbene analogs ElII(OCH2CH2NMe2)2 and ClElIIOCH2CH2NMe2 (ElII = Ge, Sn, Pb)

Vibrational spectra of compounds of divalent Group 14 elements El^II(OCH₂CH₂NMe₂)₂ with El^II = Ge (1), Sn (2), Pb (3) and ClEl^IIOCH₂CH₂NMe₂ with El^II = Ge (4) and Sn (5) were measured for the first time and analyzed within the framework of DFT calclations. Monomeric compounds 1 and 2 whose molecules are stabilized only through intramolecular coordination were confirmed to be isostructural. Unlike 1 and 2, plumbylene 3 is a polymer in both solution and the crystalline state; the latter was confirmed by X-ray diffraction analysis. The ν^s _C-N stretching frequency in the CH₂NMe₂ fragment was shown to decrease by 80–100 cm⁻¹ owing to the formation of the coordination bond El←N. To elucidate the mechanism of a dynamic flip-flop process suggested earlier based on the broadening of some signals in the NMR spectra of compounds 1 and 4, the Raman spectra of solutions of compounds 1 and 2 in THF and Py were obtained. These experiments revealed no equilibrium with participation of a stable form with one coordination bond El←N cleaved along with the starting molecule. This is consistent with the results of the corresponding quantum chemical calculations of thermo-dynamic parameters. A somewhat different, more probable mechanism of the dynamic process was proposed, which involves an overturn of the CH₂NMe₂ fragment with cleavage of the El←N bond in the transition state only.     

Potassium-conducting solid electrolytes in the systems K2 ? 2xAl2 ? xMxO4 (M = Nb, Ta)

New potassium-monoaluminate-based solid electrolytes with high potassium-cationic conductance are synthesized, by partial substitution of penta-charged cations Nb⁵⁺ and Ta⁵⁺ for Al³⁺ cations, and studied. Both additives increased drastically the KAlO₂ conductivity over the entire studied temperature range. The reason for the increase in the potassium monoaluminate conductivity, on the introducing of the studied additives, is the formation of potassium vacancies as a result of the substitution reaction Al³⁺ → Nb⁵⁺(Ta⁵⁺) + 2V’c, as well as broadening of the region of existence of the KAlO₂ high-temperature γ-modification whose transport properties exceed those of the low-temperature β-form.