The contribution of the <$E roman Ca sup 2+>-induced <$E roman Ca sup 2+> release (CICR) mechanism in excitation-contraction coupling and the tightness of the coupling between <$E roman Ca sup 2+> influx and <$E roman Ca sup 2+> release have been still controversial in smooth muscle cells (SMC). In SMC isolated from the guinea-pig vas deferens or urinary bladder, a depolarizing stimulus initially induced spot-like increases in the intracellular <$E roman Ca sup 2+> concentration (<$E [ roman Ca sup 2+ ] sub i>), called "<$E roman Ca sup 2+> hot spots", at several superficial areas in the cell. When a weak stimulus (a small or a short depolarizing step) was applied, only a few <$E roman Ca sup 2+> hot spots appeared transiently in the superficial area but did not spread into other regions, to trigger global <$E [ roman Ca sup 2+ ] sub i> rise. Such depolarization-evoked local <$E roman Ca sup 2+> transients were distinctive from spontaneous <$E roman Ca sup 2+> sparks, since the former were susceptible to <$E roman Ca sup 2+> blockers, ryanodine, and inhibitors of the <$E roman Ca sup 2+> pump in the sarcoplasmic reticulum (SR), suggesting pivotal roles of <$E roman Ca sup 2+> influx through voltage-dependent <$E roman Ca sup 2+> channels (VDCC) and <$E roman Ca sup 2+> release from the SR through ryanodine receptors (RyR) for the activation of <$E roman Ca sup 2+> spots. Frequently discharging <$E roman Ca sup 2+> spark sites under resting conditions were located exactly in the same areas as <$E roman Ca sup 2+> hot spots evoked by depolarization, indicating the

existence of distinct local junction sites for tight coupling between VDCC in the plasmalemma and RyR in the SR. Co-localization of clusters of RyR and large-conductance <$E roman Ca sup 2+>-activated <$E roman K sup +> channels was also suggested. The fast and tight coupling for CICR in these junctional sites was triggered also by an action potential, whereas a slower spread of <$E roman Ca sup 2+> wave to the whole-cell areas suggests the loose coupling in propagating CICR to other cell areas. It can be, therefore, postulated that CICR may occur in two steps upon depolarization; the initial CICR in distinct junctional sites shows tight coupling between <$E roman Ca sup 2+> influx and release, and the following CICR may propagate slow <$E roman Ca sup 2+> waves to other areas. Ryanodine receptors form a multiprotein complex with molecules, such as calsequestrin, junctin, triadin, junctophilins, and FK506-binding proteins, which directly or indirectly regulate the RyR activity and the tight coupling. Moreover, an evoked <$E roman Ca sup 2+> spot may enhance <$E roman Ca sup 2+> uptake by neighboring mitochondria and their ATP production to increase energy supply to the <$E roman Ca sup 2+> pump of the SR in the microdomain.

Теорему про спільну нерухому точку, що була встановлена Чжаном і Суном у 2009 році, поширено на узагальнені <$E ( psi ,~phi ) sub {f , g}>-слабкі стискуючі відображення. Наведено приклад, що ілюструє основний результат. Одержано деякі результати про спільну нерухому точку для відображень, що задовольняють умову стиску інтегрального типу у повних метричних просторах.

The photoinduced domino effect for the phase transition dynamics in one-dimensional electron-lattice systems is investigated to clarify the dependence on the friction and interaction between neighboring sites. We find a novel photoinduced domino process in the case of strong intersite interaction and weak friction. In this domino motion, the photoexcited site is still in an excited electronic state, which is in striking contrast to the conventional domino. This mechanism explains the photoinduced phase transitions in systems which have a large-size nucleus of the developing new phase.

Освещен вопрос, касающийся решения проблемы обнаружения слабых аналоговых сигналов на фоне сильного шума с обеспечением гораздо большего выигрыша в отношении сигнал/шум в сравнении с уже существующими техническими решениями. Рассмотрено устройство обработки сигналов, описана сущность способа, условия достижения поставленной задачи получения максимального выигрыша в отношении сигнал/шум, превышающего 50 дБ, и преимущества рассмотренного устройства, которое является эффективным для систем обработки информации с малым уровнем мощности.

In this paper, we are interested in solving the Lagrange partial differential equation of the fourth order, which governs the deformation of a thin silicon square membrane, perfectly embedded and subjected to a uniform static pressure in the case of the weak disturbances. The proposed approach that consists of using the Galerkin method with trigonometrical basis functions is simple, easy to implement and ensures a good stability of the algorithm and a satisfactory accuracy.

The influence of X-ray and magnetic fields on the formation of radiation defects in silicon temperature sensors is investigated by the method of capacitance spectroscopy. It is shown that the defects which are generated by X-ray radiation are more sensitive to weak magnetic fields in comparison with structural defects. Effects of weak magnetic fields (B = 0,17 Tl) on the pattern changes VFC of barrier structures are opposite to the action of X-ray radiation.

It has been shown from the Poisson equation that the presence of deep levels in the semiconductor bandgap influences in a complicated manner upon distribution of the space charge, potential and electrical fields in the Schottky diode. Under high reverse bias, however, the diode characteristics become standard. To achieve semi-insulating conductivity in CdTe, it is impossible to widen considerably the depleted layer in the diode. Therefore, the region of the high electric field is only a small part of the substrate thickness. Too small capacitance value and its weak dependence on the bias voltage observed in the Schottky diode made of semi-insulating CdTe are a result of the effect of the substrate resistance and the wide space-charge region in the diode.

Наведено аналіз впливу вітрових турбін на електричничі мережі з малою пропускною здатністю та запропоновано рекомендації щодо їх використання під час розробки нових проектів.

Andreev reflection in contacts based on a magnetic superconductor Mo3Sb7 in magnetic field has been investigated by the point-contact method. It is found that the behavior of the order parameter in the magnetic field <$E DELTA (H)> is essentially dependent on the value of <$E DELTA>, which varies widely (<$E DELTA (0,~0)~symbol Ы~0,01~-~0,31> meV) for different contacts at practically invariant <$E T sub c>. At high <$E DELTA> the dependence <$E DELTA sub max (H)> deviates slightly from the theoretical prediction applicable under the point-contact conditions. As the order parameter decreases, the deviation starts to increase and becomes very large when <$E DELTA> approaches its minimum. Proceeding from the results obtained in this study and from the temperature measurements on Mo3Sb7 performed formely, we are inclined as before to assign the compound to the class of superconductors with the anisotropic gap function. So, it in no way can be considered as an conventional BCS-type superconductor. The upper critical field <$E H sub c2~symbol @~16,5> kOe found here is close to that obtained from magnetization measurements in other study. According to the estimation performed, the pair-breaking effect of the Pauli paramagnetism is rather weak in Mo3Sb7.

We search for marginal Fermi-liquid behavior in the two-band Hubbard model with one narrow band. We consider the limit of low electron densities in the bands and strong intraband and interband Hubbard interactions. We analyze the influence of electron - polaron effect and other mechanisms of mass-enhancement (related to momentum dependence of the self-energies) on effective mass and scattering times of light and heavy components in the clean case (electron - electron scattering and no impurities). We find the tendency towards phase-separation (towards negative partial compressibility of heavy particles) in a 3D case for large mismatch between the densities of heavy and light bands in a strong coupling limit. We also observe that for low temperatures and equal densities the resistivity in a homogeneous state R(T) ~ T<^>2 behaves in a Fermi-liquid fashion both in 3D and 2D cases. For temperatures higher then effective bandwidth for heavy electrons <$E T~>>~W sub h sup *> the coherent behavior of heavy component is totally destroyed. The heavy particles move diffusively in the surrounding of light particles. In the same time the light particles scatter on the heavy ones as if on immobile (static) impurities. In this regime the heavy component is marginal, while the light one is not. The resistivity goes on saturation for <$E T~>>~W sub h sup *> in the 3D case. In 2D the resistivity has a maximum and localization tail due to weak-localization corrections of Altshuler - Aronov type. Such behavior of resistivity in 3D could be relevant for some uranium-based heavy-fermion compounds like UNi2Al3

and in 2D for some other mixed-valence compounds possibly including the layered manganites. We also consider briefly the superconductive (SC) instability in the model. The leading instability is towards p-wave pairing and is governed by enhanced Kohn - Luttinger mechanism of SC at low electron density. The critical temperature corresponds to the pairing of heavy electrons via polarization of the light ones in 2D.

Індекс рубрикатора НБУВ: В317.23 + В317.242

Рубрики:

Квантова статистика

Теорія фазових переходів 2 роду

Шифр НБУВ: Ж14063 Пошук видання у каталогах НБУВ 
Повний текст  Наукова періодика України 

Purpose. Genetic algorithm is a kind of random search method evolved from the genetic mechanism, it has strong robustness and optimization ability. However, a large number of researches indicated that the traditional genetic algorithms have many deficiencies and limitations in global multimodal optimization, such as they are prone to premature convergence, high computational cost and weak local search abilities. The purpose is to overcome these disadvantages through the creation of a new algorithm for solving global multimodal optimization problems, which is self-adaptive dynamic niche genetic algorithm (SDNGA). Methodology. By studying the GA optimization and niche theory, we combine multi-groups and niche method to traditional genetic algorithm, which is used in the solution of global multimodal optimization problems. The proposed algorithm is applied to test functions to demonstrate its effectiveness and applicability. Findings. We adopted the niche technology to divide each generation of a group into several subgroups. Then, we choosed the best individual from each subgroup as the representative of such a subgroup, and then carried out the hybridization and mutation to produce a new generation within the population and between populations, thus enhancing the global optimization ability of the algorithm, and improving the convergence speed. Originality. We made a study of genetic algorithm and niche theory to apply in the global multimodal optimization problem. We discussed the ideas and the steps of proposed algorithm, made the qualitative analysis on the searching ability and the convergence speed. The research on this aspect has not been found at present. Practical value. We proposed a self-adaptive dynamic niche genetic algorithm, which can be used in global multimodal optimization problems. The test experimental results have shown that SDNGA has good searching ability, good performance and very strong robustness, which allows for solutions of higher quality.

The purpose of our work was to conduct biological and analytical studies of the peritoneal dialysis (PD) solutions containing glucose and sodium lactate and establish correlations between cell viability of the Vero cell line and values of analytical indexes of the tested solutions. The results of this study confirm the cytotoxicity of the PD solutions even compared with the isotonic solution of sodium chloride, which may be due to the low pH of the solutions, presence of glucose degradation products (GDPs) and high osmolarity of the solutions, and unphysiological concentrations of glucose and sodium lactate. However, it is not yet known what factors or their combination and to what extent cause the cytotoxicity of PD solutions. In the neutral red (NR) test the weak, almost middle (r = -0,496 and 0,498, respectively) and unexpected correlations were found between reduced viability of monkey kidney cells and increased pH of the PD solutions and between increased cell viability and increased absorbance at 228 nm of the tested PD solutions. These two correlations can be explained by a strong correlation (r = -0,948) between a decrease in pH and an increase in the solution absorbance at 228 nm. The opposite effect was observed in the MTT test. The weak, but expected correlations (r = 0,32 and -0,202, respectively) were found between increased cell viability and increased pH in the PD solutions and between decreased cell viability and increased absorbance at 228 nm of the tested PD solutions. The middle and weak correlations (r = 0,56 and 0,29, respectively) were detected between increased cell viaіbility and increased lactate concentration in the NR test and MTT test. The data of these correlations can be partially explained by the fact that a correlation with a coefficient r = -0,34 was found between decreased pH in the solutions and increased lactate concentration. The very weak correlations (0,138 and 0,196, respectively) were found between increased cell viability and increased glucose concentration in the NR test and MTT test. These experimental data indicate that pH is the dominating factor, which determines almost all of the established correlations. However, the character of the correlations is quite different: the higher the pH, the greater was the cell viability in the MTT test, and conversely, the higher the pH, the lower was the cell viability in the NR test. Secondly, the unexpected correlation coefficient was determined as -0,473 between decreased cell viability in the MTT test and increased cell viability in the NR test. Moreover, this phenomenon indicates that the mitochondrial enzyme succinate dehydrogenase is more vulnerable to the action of PD solutions than membrane permeability. Finally, we conclude that the NR test is not suitable for comparative studies of PD solutions which differ in pH, as it is pH dependent and does not enable the comparison of plausible cell viability.

Purpose. Stratified shale formation is prone to collapse in drilling. A method of precise calculation of collapse pressure should be developed to avoid severe wellbore instability of stratified shale. Methodology. Clay mineral components of stratified shale were measured by X-ray diffraction, and micro-structures of stratified shale were observed by scanning electron microscope. Shale cores had been drilled under different dip angles and then immersed in drilling fluids. Strength, cohesion and internal friction angle of stratifications and rock mass (vertical to the stratifications) were measured over different immersion time. The method suitable for calculating stratified shale strength has been developed. Based on the strength calculation method and circumferential stress distribution equation, the collapse pressure of stratified shale has been calculated. Findings. The stratified shale is mainly composed of illite and kaolinite; and stratifications are actually 500 nm - 30 <$Emu>m wide microcracks (stratified shale of Weizhou formation, Beibuwan basin, South China Sea). Cohesion and internal friction angle of stratification decrease in exponential rule with immersion time, while that of the rock mass decrease in linear rule with immersion time. The rock strength decreases firstly and then increases with the dip angle (<$E 0~-~90 symbol Р>); and the lowest value occurs at the dip angle 50 - 60; and single weak plane criterion is suitable for calculation of the strength of stratified shale. Contrasted to the drilling fluid density and wellbore stability situation while drilling stratified shale formation, it can be obtained that the numerical results of collapse pressure are quite precise. Originality. Stratifications are microcracks developed in shale, and free water could seep inward shale through stratifications under capillary force. The method of calculating collapse pressure of stratified shale taking into account the seepage effect has been developed. Practical value. The research results allow us to calculate precisely the collapse pressure of stratified shale under different deviation angles and azimuth angles. This contributes to optimization of drilling fluids density, wellbore trajectory and configuration while drilling in stratified shale.

Вивчено обмеженість слабких розв'язків для недіагональної параболічної системи сингулярних квазілінійних диференціальних рівнянь з матрицею коефіцієнтів, що задовольняє спеціальні структурні умови. Для цього застосовується техніка, що базується на оцінці лінійних комбінацій невідомих.

<$E L sup inf>-оцінки слабких розв'язків встановлено для квазілінійної недіагональної параболічної системи сингулярних рівнянь, матриця коефіцієнтів якої задовольняє спеціальні структурні умови. Використано техніку, що базується на оцінці лінійних комбінацій невідомих.

For overdoped cuprates, it is believed that the normal state behaves as an ordinary Fermi liquid while the superconducting state conforms to the BCS theory. We have put these beliefs to the test by a comprehensive experiment in which over two thousand cuprate films were synthesized by molecular beam epitaxy and studied in great detail and precision. Here, we compare our key experimental results to various proposed explanations based on BCS theory extended to dirty d-wave superconductors, including the cases of strong (unitary) and weak (Born) scattering on impurities. The discrepancies seem insurmountable, and point to the need to develop the theory further, likely beyond the canonical BCS paradigm.

In this work, the influence of weak magnetic field on structure-dependent properties of micro-structured Si was determined. The researches of EPR-spectra inherent to micro-structured Si showed the presence of the spectral line at H ~ 3500 Oe that appears from centers with the g-factor g ~ 2,0010 (pB-centers). Intensity of the determined spectral line decreases twice after magnetic processing. The observed redox processes and evolution of defect structure are interpreted as the influence of magnetic field on micro-structured Si. Calculations made using the data of X-ray diffractometric researches showed an essential decrease of internal strains and respective increase of the lattice parameter in micro-structured Si samples after magnetic processing in the weak magnetic field.

Індекс рубрикатора НБУВ: В379.273

Рубрики:

Магнітні властивості напівпровідників

Шифр НБУВ: Ж16425 Пошук видання у каталогах НБУВ 
Повний текст  Наукова періодика України 

We consider the charge and spin effects in low dimensional superconducting weak links. The first part of the review deals with the effects of electron - electron interaction in Superconductor/Luttinger liquid/Superconductor junctions. The experimental realization of this mesoscopic hybrid system can be the individual single wall carbon nanotube that bridges the gap between two bulk superconductors. The dc Josephson current through a Luttinger liquid is evaluated in the limits of perfectly and poorly transmitting junctions. The relationship between the Josephson effect in a long SNS junction and the Casimir effect is discussed. In the second part of the paper we review the recent results concerning the influence of the Zeeman and Rashba interactions on the thermodynamical properties of ballistic S - QW - S junction fabricated in two dimensional electron gas. It is shown that in magnetically controlled junction there are conditions for resonant Cooper pair transition which results in giant supercurrent through a tunnel junction and a giant magnetic response of a multichannel SNS junction. The supercurrent induced by the joint action of the Zeeman and Rashba interactions in 1D quantum wires connected to bulk superconductors is predicted.

The Raman optical activity (ROA) of magnons in rutile-structure antiferromagnetic FeF2 (<$E T sub N ~=~78> K) has been studied as a function of temperature and applied magnetic field. For exciting light incident along the с axis, ROA is observed for magnons but not for phonons. In zero field, a small splitting (0,09 <$E roman cm sup -1>) of the two acoustic - magnon branches is observed for the first time by inelastic light scattering. The splitting in applied magnetic field is found to reduce with increasing temperature in accordance with theory. No ROA was detected for two-magnon excitations. In optical absorption measurements performed over thirty years ago, a very small circular dichroism (CD) was observed in the magnon sidebands of other simple rutile antiferromagnetic fluorides (MnF2 and CoF2). The origin of this CD was not understood at the time. The Raman studies of the one-magnon Raman scattering in FeF2 have demonstrated that in zero field the degeneracy of the antiferromagnetic magnon branches is lifted by a weak magnetic dipole - dipole interaction, as predicted by Pincus and Loudon and by White four decades ago. The source of the observed CD in the magnon sidebands can now be traced to this same magnetic - dipole induced splitting.