To the evaluation of the potential biologic resources of the world ocean

An approach to the evaluation of the potential bio-productivity on the basis of mathematical modelling is discussed. To determine the potential productivity of biomass of this species that may be removed annually from the area of its habitation during an indefinitely long period. Over the long term, this catch of marine organisms will act on the natural substance circulation in the sea at increasing spatial scales. It is proposed to model the bioproduction processes by successive evaluation of biogenic substance resources which take part in these cisculations

Search for long-lived states in antiprotonic lithium

The spectrum of the (L_i^3 + p-bar + 2e) four-body system was calculated in an adiabatic approach. The two-electron energies were approximated by a sum of two single-electron effective charge two-center energies as suggested in [6]. While the structure of the spectrum does not exclude the existence of long-lived states, their experimental observability is still to be clarified

Parametric instability of surface waves at the second harmonic of ion cyclotron frequency

Parametric instability of surface waves at the second harmonic of ion cyclotron frequency (SWCF) in plasma filled dielectric planar waveguide is examined in a kinetic approximation. SWCF are extraordinary polarized modes propagating across the external steady magnetic field. Simple analytical expressions for the SWCF frequencies, their damping rates due to collisions between plasma particles and interactions between plasma particles and plasma interface, increments of the parametrical instabilities are found. Increments of the SWCF parametric instabilities are slightly dependent on the transverse dimensions of the plasma layer and they strongly decrease with the SWCF wavelength. The obtained results can be used in controlled fusion researches in order to avoid undesirable regime of the plasma periphery heating in fusion devices during.Параметрична нестійкість поверхневих хвиль на другій гармоніці іонної циклотронної частоти (ПЦХ) в діелектричних хвилеводах з плазмовим заповненням досліджена в кінетичному наближенні. ПЦХ є незвичайно поляризованими модами, що поширюються поперек зовнішнього сталого магнітного поля. Знайдено прості аналітичні вирази для частот ПЦХ, їх декрементів загасання, обумовлених зіткненнями частинок плазми між собою та їх взаємодією з межею плазми, а також інкрементів їх параметричної нестійкості. Інкременти параметричної нестійкості ПЦХ слабко залежать від поперечних розмірів плазми та сильно зменшуються із збільшенням довжини хвилі ПЦХ. Здобуті результати можна використовувати в термоядерних дослідження для визначення небажаних режимів нагрівання периферії плазми, яких слід уникати при ІЦРН.Параметрическая неустойчивость поверхностных волн на второй гармонике ионной циклотронной частоты (ПЦВ) в диэлектрических волноводах с плазменным заполнением исследована в кинетическом приближении. ПЦВ являются необыкновенно поляризованными модами, распространяющимися поперек внешнего постоянного магнитного поля. Найдены простые аналитические выражения для частот ПЦВ, их декрементов затухания, обусловленных столкновениями частиц плазмы между собой и их взаимодействием с границей плазмы, а также инкрементов их параметрической неустойчивости. Инкременты параметрической неустойчивости ПЦВ слабо зависят от поперечных размеров плазмы и сильно уменьшаются при увеличении длины волны ПЦВ. Полученные результаты могут быть использованы в исследованиях по термоядерному синтезу для определения нежелательных режимов нагревания периферии плазмы, которых следует избегать при ИЦРН

Self-consistency and collective effects in semiclassical pairing theory

A simple model, in which nuclei are represented as homogeneous spheres of symmetric nuclear matter, is used to study the effects of a self-consistent pairing interaction on the nuclear response. Effects due to the finite size of nuclei are suitably taken into account. The semiclassical equations of motion derived in a previous paper for the time-dependent Hartree-Fock-Bogoliubov problem are solved in an improved (linear) approximation in which the pairing field is allowed to oscillate and to become complex. The new solutions are in good agreement with the old ones and also with the result of well-known quantum approaches. The role of the Pauli principle in eliminating one possible set of solutions is also discussed. The pairing-field fluctuations have two main effects: they restore the particle-number symmetry which is broken in the constant-$\Delta$ approximation and introduce the possibility of collective eigenfrequencies of the system due to the pairing interaction. A numerical study with values of parameters appropriate for nuclei, shows an enhancement of the density-density strength function in the region of the low-energy giant octupole resonance, while no similar effect is present in the region of the high-energy octupole resonance and for the giant monopole and quadrupole resonances.Comment: 31 pages, 6 eps figure

Effect of macrostructure on the thermoelectric properties of biomorphous SiC/Si ceramics

In this work, effect of porous macrostructure on the thermoelectric properties of biomorphous SiC/Si ceramics prepared by the liquid silicon infiltration process has been investigated. Temperature dependences of the conductivity and thermal e.m.f. have been measured within the range 20-700 °C. It has been shown that electrical resistivity of the samples decreases drastically as temperature increases over the entire temperature range, indicating semiconductor behavior. All the samples demonstrate a negative thermal e.m.f. confirming the electronic mechanism of charge transfer. It is ascertained that anisotropy of porous macrostructure of the ceramics influences considerably on their electric and thermoelectric properties. The figure of merit maximum value of 1.2×10⁻⁵ K⁻¹ at 700 °C was obtained

Biomorphic SiC from peas and beans

Biomorphic porous SiC ceramics produced by impregnation with liquid or vapor silicon of carbon matrices derived from peas (Pisum sativum L.) and beans (Phaseolus) precursors were investigated. Optical and scanning electron microscopy was used to study the structure of ceramics. It was shown that SiC ceramics made from endosperm of peas and beans seeds has inherited the alveolate structure and possesses many hierarchical pores with diameters varying between 20 to 100 µm. Raman spectroscopy investigations showed that the 3C polytype is formed at a synthesis temperature of about 1550 ⁰C, and that both 3C and 6H-SiC are formed at temperatures of about 1800 ⁰C. It is shown possibilities of production of ceramic articles of various forms from seeds

Effect of Si Infiltration Method on the Biomorphous SiC Microstructure Properties

Two types of wood-based biomorphous SiC composites with different microstructure are obtained by infiltration of carbon template with liquid or vapour silicon. The oak, pine, lilac, walnut, acacia woods available in Ukraine are used as the biological template in this work. The SEM, optical and EPR data indicate that biomorphous SiC obtained by melt infiltration consists of crystalline 3C-SiC phase while that obtained by vapour infiltration consists of both crystalline and amorphous 3C-SiC phase.Були одержані два типи деревного біоморфного SiC-композиту з різною мікроструктурою просочення вуглецевого шаблону газоподібним або рідким кремнієм. Деревина дуба, сосни, бузку, волоського горіха, акації, які поширені в Україні, використовувалися як біологічний шаблон у цій роботі. Дані оптичні, СЕМ і ЕПР показали, що одержані просоченням розтопом біоморфні композити SiC складаються із кристалічної й аморфної фаз 3C-SiC.Были получены два типа древесного биоморфного SiC-композита с различной микроструктурой пропитки углеродистого шаблона газообразным или жидким кремнием. Древесина дуба, сосны, сирени, грецкого ореха, акации, распространенные в Украине, использовались как биологический шаблон в этой работе. Данные оптические, СЭМ и ЭПР показали, что полученные пропиткой расплавом биоморфные композиты SiC состоят из кристаллической и аморфной фаз 3C-SiC

Effect of Si infiltration method on the properties of biomorphous SiC

Two types of wood-based biomorphous SiC composites with different microstructure were obtained by infiltration of carbon template with liquid or vapour silicon. The oak, pine, lilac, walnut, acacia woods available in Ukraine were used as the biological template in this work. SEM, optical and AFM data indicated that biomorphous SiC obtained by melt infiltration consists of crystalline phase of 3C-SiC, while that of vapor infiltration results in formation of crystalline and amorphous phases of 3C-SiC. The same results were obtained for infiltration of carbon fibers. Thus, it was suggested that the mechanism of SiC formation is governed by the infiltration method

Interaction of the single-particle and collective degrees of freedom in non-magic nuclei: the role of phonon tadpole terms

A method of a consistent consideration of the phonon contributions to mass and gap operators in non-magic nuclei is developed in the so-called g^2 approximation, where g is the low-lying phonon creation amplitude. It includes simultaneous accounting for both the usual non-local terms and the phonon tadpole ones. The relations which allow the tadpoles to be calculated without any new parameters are derived. As an application of the results, the role of the phonon tadpoles in the single-particle strength distribution and in the single-particle energies and gap values has been considered. Relation to the problem of the surface nature of pairing is discussed.Comment: 22 pages, 7 figure

Synthesis and luminescent properties of SrTiO₃:Pr³⁺ phosphors prepared by sol-gel method

New red SrTiO₃:Pr³⁺ phosphor for the field emission displays application was prepared using the sol-gel method. The reaction between starting materials SrCl₂, Ti-(Oi-C₃H₇)₄ and PrCl₃ resulted in a mix of compounds transformed to single-phase SrTiO₃:Pr after its annealing in air. Optimal technological conditions for preparation of efficiently radiating SrTiO₃:Pr³⁺ phosphors were found. Both photoluminescence and cathodoluminescence spectra showed the high intensity red peaks at the wavelength λmax = 617 nm. The high luminance of 300 cd/m² was obtained at the anode voltage of 10 kV