On decay of large amplitude bubble of disoriented chiral condensate

The time evolution of initially formed large amplitude bubble of disoriented chiral condensate (DCC) is studied. It is found that the evolution of this object may have a relatively long pre-decay stage. Simple explanation of such delay of the DCC bubble decay is given. This delay is related to the existence of the approximate solutions of multi-soliton type of the corresponding radial sine-Gordon equation in (3+1) dimensions at large bubble radius.Comment: 6 pages, LaTeX, 5 PostScript figure

Metal-insulator transition induced by 16O -18O oxygen isotope exchange in colossal negative magnetoresistance manganites

The effect of 16O-18O isotope exchange on the electric resistivity was studied for (La(1-y)Pr(y))0.7Ca0.3MnO3 ceramic samples. Depending on y, this mixed perovskite exhibited different types of low-temperature behavior ranging from ferromagnetic metal (FM) to charge ordered (CO) antiferromagnetic insulator. It was found that at y=0.75, the substitution of 16O by 18O results in the reversible transition from a FM to a CO insulator at zero magnetic field. The applied magnetic field (H >= 2 T) transformed the sample with 18O again to the metallic state and caused the increase in the FM transition temperature Tc of the 16O sample. As a result, the isotope shift of Tc at H = 2 T was as high as 63 K. Such unique sensitivity of the system to oxygen isotope exchange, giving rise even to the metal-insulator transition, is discussed in terms of the isotope dependence of the effective electron bandwidth which shifts the balance between the CO and FM phases.Comment: 5 pages (RevTeX), 2 eps figures included, to appear in J. Appl. Phys. 83, (1998

ОПРЕДЕЛЕНИЕ СУММАРНОГО СОДЕРЖАНИЯ ФЕНОЛЬНЫХ АН-ТИОКСИДАНТОВ В МОДЕЛЬНЫХ СМЕСЯХ ПО МЕТОДУ ФОЛИНА-ЧОКАЛЬТЕУ И ПО МЕТОДУ FRAP

The total content of phenolic antioxidants (PhA) in tea, wine and other foodstuffs is usually determined without their separation. Active oxidizing agents, mainly Folin-Ciocalteu reagent (FC), are used as group reagents. The results obtained with the FC assay and later recalculated to the standard substance vary significantly from the results obtained with the other spectrophotometric assays such as the FRAP assay. In order to elucidate the real reason of the above-mentioned discrepancies, the authors have analyzed the water solutions with the known PhA total content (10-5–10-4 mol/dm3). The correct results were obtained only for one-component solutions. For the model mixtures containing 2 or 3 components, the results of cΣ  measurement with the standard FC procedure were distorted with significant systematic errors. When the universally used standard (gallic acid) has been applied, the error values (δс) were positive to the point of 50 % rel.; for the other standards the corresponding errors were much greater (by modulo). The main source of systematic errors during the PhA total content estimation was an intragroup selectivity of the signals. This effect could be related to the reaction stoichiometry features when FC reacts with the individual polyphenols. The subsidiary source of the systematic errors was the non-additivity of the light absorbance by the reaction products (reduced forms of the FC-reagent). For some mixtures, the deviations from the additivity were near 20% rel., this effect was detected for the first time. The substitution of the FC reagent with a less active oxidizing agent (FRAP reagent: Fe3+ + 2,2'-dipyridil) during cΣdetermination depressed the intragroup selectivity of the signals and totally prevented the non-additivity of the light absorbance. These effects assured more correct estimates of the total PhA content (δс 25 %).  In addition, the FPAP assay was more sensitive and more specific method to determine the total polyphenols than the widely used FC assay. Therefore, authors recommend replacing the FC assay with the FRAP assay in the food industry to improve the quality control performance of tea, wines and other foodstuffs.Keywords: phenolic antioxidants, total content of polyphenols, spectrophotometry, model mixtures, Folin-Ciocalteu assay, FRAP assay, systematic errorsDOI: http://dx.doi.org/10.15826/analitika.2019.23.3.008(Russian)V.I. Vershinin, E.V. Belova Dostoevsky Omsk State University, Mira str., 55a, Omsk, 644077, Russian FederationСуммарное содержание фенольных антиоксидантов (ФА) в пищевых продуктах обычно определяют без разделения смесей ФА, используя реактив Фолина-Чокальтеу (ФЧ) в качестве группового реагента. Как правило, результаты анализа, полученные методом ФЧ и выраженные в пересчете на стандартное вещество (Хст), намного выше результатов анализа тех же продуктов другими спектрофотометрическими методами, в частности методом FRAP (ferric reducing antioxidant power). Чтобы выяснить причины наблюдаемых расхождений, провели сопоставительный анализ водных растворов с известным содержанием ФА (10-5–10-4 моль/л). Методом ФЧ правильные результаты удается получить только в ходе анализа однокомпонентных растворов. Суммарное содержание ФА в модельных смесях методом ФЧ определяется с большими систематическими погрешностями (δс). При использовании галловой кислоты в качестве Хст значения δс доходят до 50 % отн., результаты анализа обычно завышены. Применение других Хст ведет к еще большим (по модулю) погрешностям. Установлено, что главным источником этих погрешностей является внутригрупповая селективность сигналов, вероятно обусловленная разной стехиометрией окисления индивидуальных ФА. Дополнительным источником погрешностей является неаддитивность светопоглощения продуктов восстановления реактива ФЧ смесями ФА; этот эффект выявлен впервые. Для некоторых смесей отклонения от аддитивности (ОА) доходят до 20 %. Таким образом, независимо от природы выбранного стандарта метод ФЧ не позволяет правильно оценить суммарное содержания ФА в неразделенных смесях. Переход к методу FRAP (система Fe3+ + 2,2'-дипиридил) обеспечил снижение внутригрупповой селективности и аддитивность сигналов. Анализ модельных смесей ФА по методу FRAP дает более правильные результаты (δс 25%). Кроме того, метод FRAP более чувствителен и более специфичен для данной группы аналитов. Поэтому замена метода ФЧ методом FRAP должна повысить надежность контроля качества чая, вин и других пищевых продуктов по показателю «суммарное содержание полифенолов».   Ключевые слова: фенольные антиоксиданты, суммарное содержание полифенолов, модельные смеси, спектрофотометрия, метод Фолина-Чокальтеу, метод FRAP, систематические погрешности.DOI: http://dx.doi.org/10.15826/analitika.2019.23.3.00

Kink-antikink interactions in the double sine-Gordon equation and the problem of resonance frequencies

We studied the kink-antikink collision process for the "double sine-Gordon" (DSG) equation in 1+1 dimensions at different values of the potential parameter $R>0$. For small values of $R$ we discuss the problem of resonance frequencies. We give qualitative explanation of the frequency shift in comparison with the frequency of the discrete level in the potential well of isolated kink. We show that in this region of the parameter $R$ the effective long-range interaction between kink and antikink takes place.Comment: 9 pages, LaTeX, 4 figures (eps

Development of Hydrometallurgical Process of Non-Ferrous and Rare Metals Recovery from Untraditional Mineral Raw Materials and Natural Brines

In connection with gradual lowering of supplies of tradit- ional ore raw materials involving non-ferrous and rare metals, winch is treated by well-known technologies, invo-lving into the production of untraditional, secondary and technogeneous raw materials appears to be actual task

Self-diffusion in a triple-defect A-B binary system : Monte Carlo simulation

In this comprehensive and detailed study, vacancy-mediated self-diffusion of A- and B-elements in triple-defect B2-ordered ASB1-S binaries is simulated by means of a kinetic Monte Carlo (KMC) algorithm involving atomic jumps to nearest-neighbour (nn) and next-nearest-neighbour (nnn) vacancies. The systems are modelled with an Ising-type Hamiltonian with nn and nnn pair interactions completed with migration barriers dependent on local configurations. Self-diffusion is simulated at equilibrium and temperature-dependent vacancy concentrations are generated by means of a Semi Grand Canonical MC (SGCMC) code. The KMC simulations reproduced the phenomena observed experimentally in Ni-Al intermetallics being typical representatives of the 'triple-defect' binaries. In particular, they yielded the characteristic ‘V’-shapes of the isothermal concentration dependencies of A- and B-atom diffusivities, as well as the strong enhancement of the B-atom diffusivity in B-rich systems. The atomistic origins of the phenomenon, as well as other features of the simulated self-diffusion such as temperature and composition dependences of tracer correlation factors and activation energies are analyzed in depth in terms of a number of nanoscopic parameters that are able to be tuned and monitored exclusively with atomistic simulations. The roles of equilibrium and kinetic factors in the generation of the observed features are clearly distinguished and elucidated

The bubbles of matter from multiskyrmions

The multiskyrmions with large baryon number B given by rational map (RM) ansaetze can be described reasonably well within the domain wall approximation, or as spherical bubbles with energy and baryon number density concentrated at their boundary. A special class of profile functions is considered approximating the true profile and domain wall behaviour at the same time. An upper bound is obtained for the masses of RM multiskyrmions which is close to the calculated masses, especially at large B. The gap between rigorous upper and lower bounds for large B multiskyrmions is less than 4%. The basic properties of such bubbles of matter are investigated, some of them being of universal character, i.e. they do not depend on baryon number of configuration and on the number of flavors. As a result, the lagrangian of the Skyrme type models provides field theoretical realization of the bag model of special kind.Comment: 7 pages, no figure