Thermotaxis or motion in the field of temperature gradient is a very common phenomenon and can be found in many events in nature, from biological ones to the migration of colloidal particles. In this paper, we suggest a deterministic model to describe the collective behavior of a microorganism population with a general form of stimuli gradient-based taxis in porous media. This population has the mass density slightly heavier than the water density and forms a suspension. The suspended cells are actively in motion with a thermotaxis behavior (temperature gradient follower). Based on an Eulerian framework, the model comprises basically the Darcy equation for the fluid motion in porous media, equation of cell conservation for the microorganism population and equation of conservation for the considered stimuli. To take into account the density effects, the Boussinesq's approximation will be used. Linear stability analysis shows that there are interesting effects of temperature on the bioconvection pattern of the thermotactic microorganisms.

Cadmium compounds are highly toxic substances characterized by mutagenic, genotoxic and carcinogenic effects, and having high cumulative properties. Application of cadmium nanoparticles (NPs) in medicine stimulates the study of their mechanism of action at the cellular level and at the level of organs and systems, determination of biomarkers of their action, particularly in comparison with the ionic form. The aim of the study was to compare the features of cytotoxic and genotoxic effects of cadmium sulfide (CdS) NPs of different sizes on cell cultures of different histogenesis with those of cadmium chloride (CdCl2). In this work, we used cadmium compounds in the nanoform: NPs CdS of 4 - 6 nm and of 9 - 11 nm in size; and in the ionic form: CdCl2. The studies were conducted in vitro in cell lines - IMR-32, HEK-293 and MAEC. To count viable cells we compared the results of three basic tests: MTT (methyl tetrasolium test), SRB (sulforhodamine B test) and NRU (neutral red uptake test). We evaluated the genotoxic effect of the substances studied in vitro using DNA comet assay in alkaline conditions. CdS NPs and CdCl2 demonstrated pronounced dose-dependent cytotoxic effect in MAEC, HEK-293 and IMR-32 cell lines, by impairing membrane permeability, functioning of mitochondria and lysosomes, and inhibiting the function of protein synthesis. Cytotoxic effect of CdCl2 was the most pronounced, this effect of CdS NPs of 9 - 11 nm in size being the least pronounced. The comet DNA assay in alkaline conditions revealed a statistically significant increase in DNA comet index when exposed to CdCl2 and CdS NPs in comparison with the negative control, which indicates their genotoxic effect. CdS NPs of 4 - 6 nm in size showed a more pronounced effect in comparison with those of 9 - 11 nm in size. Conclusion: elucidation of mechanisms underlying the implementation of toxic effects of cadmium NPs will help in assessing the potential risks associated with their use in industry and developing effective preventive measures. For instance, when planning in vivo studies for toxicological evaluation of nanomaterials and nano-substances containing NPs of cadmium, it is necessary to investigate the mutagenic and carcinogenic risks and to take into account the high likelihood of neurotoxic and cardiovasotoxic effects, along with nephrotoxic effects, since high cytotoxic activity of the investigated compounds of cadmium was detected on the cells of the MAEC line (endothelial origin) and IMR-32 (neuronal origin).

This paper deal with our on-going work on the electronic spectroscopy of tetrapyrrole molecules embedded in cryogenic hosts. Under nanosecond laser excitation of the free-base tetrabenzoporphin molecules in a nitrogen matrix at 8 K, increasing the laser pulse energy results in essential enhancement of the intensity of one or several vibronic emission lines to take place in the fine-structure fluorescence spectrum. The observed intense monochromatic radiation possesses characteristics of stimulated radiation being realized as a result of a transition from the purely electronic S1 level to a vibrational sublevel of the S0 state, corresponding to excitation of stretching C - C vibrations of the tetrapyrrole methane bridges. We also report on persistent spectral hole-burning effects. The analysis of the holes and antiholes formation gives some insight on the photochemical properties of tetrabenzoporphin in a nitrogen matrix.

Індекс рубрикатора НБУВ: В368.33 + В374.7

Рубрики:

Кріокристали

Спектроскопія твердих тіл

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

It is well known that an operator-valued function <$E THETA> from the Schur class S(M, N), where M and N are separable Hilbert spaces, can be realized as a transfer function of a simple conservative discrete time-invariant linear system. The known realizations involve the function <$E THETA> itself, the Hardy spaces or the reproducing kernel Hilbert spaces. On the other hand, as in the classical scalar case, the Schur class operator-valued function is uniquely determined by its so-called "Schur parameters". In this paper we construct simple conservative realizations using the Schur parameters only. It turns out that the unitary operators corresponding to the systems take the form of five diagonal block operator matrices, which are analogs of Cantero - Moral - Velazquez (CMV) matrices appeared recently in the theory of scalar orthogonal polynomials on the unit circle. We obtain new models given by truncated block operator CMV matrices for an arbitrary completely non-unitary contraction. It is shown that the minimal unitary dilations of a contraction in a Hilbert space and the minimal Naimark dilations of a semi-spectral operator measure on the unit circle can also be expressed by means of block operator CMV matrices.

The aim of the work is to investigate ZnAs2 electrical conductivity at cyclic pressure treatment in the range of 20 - 50 GPa, to determine concrete values of pressure, at which the changes take place in this material, and to reveal peculiarities of behaviour at pressures up to 50 GPa.

Purpose - the study of content features that are inherent in the rating process and methods for forming the rating, which allow ensuring the effectiveness of procedures for decision-making. Theoretical and practical research results were obtained using the following methods: synthesis, analysis - to identify the features of the rating formation and to analyse the evaluation methods; constructive and logical methods - to construct a model of decision-making in the rating management system; logic synthesis, economic and mathematical modeling - to develop a scientific and methodological approach to rating evaluation. It was established that the basis of rating process and rating management is the concept of decision-making by potential users through the use of ratings in the implementation of the basic management functions. On the basis of the analysis, the general classification of methods for forming the rating was carried out, which enables the secure assessment procedure, effectiveness of management decisions and builds the interconnection circuit of the stages of forming the techniques rating. Classification of methods and stages of ratings formation was designed, which makes it possible to take into account the features of rating calculation in decision-making. It was proved that the determining factor is the problem of development of the theory of rating management as well as the process of development and application of scientifically based models of the rating assessment. A scheme of interconnection of formation stages of rating methodologies was built that is provided as a flexible, integrated system that encompasses techniques, methods and models in the management based on rating and allows adopting effective management decisions.

Purpose. The objective of the paper is to study antilock brake systems (ABS) effect upon the basic parameters of hydrostatic mechanical transmission (HMT) in the process of emergency braking. Methodology. The research has involved current methods of solving differential equations of mathematical model of transport vehicle braking process as well as the comparing methods to analyze braking process involving ABS and emergency braking at the expense of braking system in terms of kinematic disconnection of engine from a driving wheel with HMT of various schematic designs. Findings. As a result of the complex theoretical research, the effect of ABS upon operating pressure differential within hydrostatic drive, angular velocity of hydraulic pump shaft, range of values of angular velocity and driving and driven clutch shafts, braking efficiency of a transport vehicle, and transport vehicle deviation from the specified trajectory have been determined. Originality. It is the first time when quantitative assessment of ABS effect upon HMT kinematic and power parameters has been performed; it allows increasing technical level of transmissions even at the wheeled vehicle design stage at the expense of timely considering of possible overload occurring while operating in the process of ABS braking. Practical value. The proposed methods and applied mathematical models have made it possible to develop the approach to determine and take into account possible HMT overloads arising in terms of wheel transport vehicle with ABS braking even within the design period.

The technique of thermal vacuum deposition of Ge onto GaAs substrates has been used for obtaining nanocrystalline Ge films. Nanocrystalline character of the films is confirmed by atomic force microscopy of their surface and by the data of Raman light scattering. The most probable size of the nanocrystallites forming the films decreases monoton ically with decreasing their thickness. Electro conductivity of such the films proves to be high enough (1 - 10 <$Eroman {Ohm~cdot~cm}> at room temperature) and has a character of variable range hopping conduction of Mott's type. The hops, presumably, take place through the localized states connected with the grain boundaries.

A common opinion is that the amplitudes of harmonics in nearly sinusoidal oscillators are inversely proportional to the absolute value of the feedback return difference characterising feedback structure of this type of oscillators. And because of this fact the factor mentioned is maximized to reduce the harmonic distortion in oscillators. However, note that this approach does not take into account the fact that the ratios of amplitudes of harmonic components to amplitude of the component at fundamental frequency can change under the above procedure. In connection to this, it has been shown in this paper that the feedback return difference can not serve as a measure of hatmonic distortion in sinusoidal oscillators, at least in general.

In this paper we show that the definition of attractivity of an actual recursive digital filter can be derived from its forced-response stability, under the assumption that the attractivity property for the corresponding ideal filter is fulfilled. The statement holds for a class of input signals defined in the forced-response stability definition. The definitions of attractivity and forced-response stability are reformulated appropriatedy to take into account the effect of quantization (granularity).

Owing to the rapid multiplication of related information, the acceleration in its dissemination and the constant reduction in the costs of access to it, technology transfer processes have undergone significant transformation in recent years. Adaptation to the changing circumstances causes difficulties for several institutions even in countries with more developed economies and considerable traditions in innovation management. The transition economies of Central- and Eastern Europe, however, have to face the challenges of combating general economic fallback and establishing institutions that can enter the competition with the operating institutional system of modern economies. These latter ones also include effective technology transfer institutions. With the help of a case study, the present paper introduces how the main sources of technologies can be utilized and what basic measures universities should take in order to build up a successful technology transfer system.

The consumption of fossil fuel globally has been enormous and has reached an alarming rate resulting in fast depletion of the available resources and at the same time polluting the environment. Hence there is a growing need to take cognizance of abundant amount of inexpensive energy available in the nature especially solar energy. Development and commercialization of Photovoltaics has been in focus due to its low cost, high absorption coefficient and suitable direct band gap for solar energy conversion applications. An attempt has been made in this work to synthesize the CZTS thin films by Electro deposition and sol-gel method on indium tin oxide (ITO) glass and soda lime glass( SLG) substrates respectively. CZTS thin films have been prepared using a 3-stage electro chemical system wherein the precursors are deposited using platinum foil as a counter electrode and AgCl electrode as a reference electrode and sol-gel method. Surface morphology and optical properties have been studied using Atomic Force Microscopy, Scanning Electron Microscopy, X-ray Diffractometer and UV-Vis Spectroscopy.

This paper presents a novel approach of determining optimum intervals for aircraft maintenance. The Model of aircraft systems function state changing, offered by authors, makes possible to provide information to determine the volume, composition and execution intervals of aircraft maintenance and also enable to take into account changing components condition in an integrated manner, caused by either operating time, or service period, to determine requirements to aircraft maintenance work volume and content.

We consider in this paper the nature of the quality of the process of energy transformation in the electrical motors and also the indicators of its conversion We also show that the coefficients existing of the quality of energy transformation are effective indicators which take into account the links between the quality of energy transformation and the performances of the electric machines. In the same way the need for establishing the bond between the qualitative and quantitative characteristics of conversion was well proven.

Рассмотрена природа процесса качества преобразования энергии в электрических двигателях и показатели ее преобразования. Показано, что существующие коэффициенты качества преобразования энергии являются эффективными показателями, которые учитывают взаимосвязи между качеством преобразования энергии и работоспособностью электрической машины. Доказана необходимость учета взаимосвязей между качественными и количественными характеристиками преобразования.

Розглянуто природу процесу якості перетворення енергії в електричних двигунах і показники її перетворення. Показано, що існуючі коефіцієнти якості перетворення енергії є ефективними показниками, які враховують взаємозв'язки між якістю перетворення енергії та працездатністю електричної машини. Доведено необхідність урахування взаємозв'язків між якісними і кількісними характеристиками перетворення.

Linear correlation between the Emax (kcal/mol) of the visible electronic absorption band of four pyridazinium ylids and the empirical polarities Z (kcal/mol) defined by Kosower are established, proving the intramolecular charge transfer nature of this band. The slopes of the lines are smaller for the carbanion monosubstituted ylids, compared with those of the carbanion disubstituted ylids. This fact emphasizes the prevalence of the dipolar interactions in ylid solutions. The blue shifts recorded in the protic solvents suggest the hydrogen bond formation between the -OH of these solvents and the ylid carbanion. A linear dependence exists between the values of Emax (kcal/mol) recorded for two studied ylids. This fact demonstrates that the solvents can be arranged on the empirical scale describing their action on similar chemical compounds, in which electronic transitions of the same nature take place.

Interest into vertical take-off and landing aircraft has been renewed in recent years due to the rapid development of technology in the area and the numerous advantages іnterest into vertical take-off and landing aircraft have over traditional airplanes and helicopters. With the development of lightweight Micro-Electro-Mechanical System sensors it has become possible to construct autonomous models of Interest into vertical take-off and landing aircraft to efficiently and cost-effectively develop control concepts and compare design variations. This paper focuses on the design and construction of an autonomous quad rotor aircraft. A mathematical model of the system has been developed and used as the basis of a suitable controller designed. A Kalman filter has also been designed and incorporated into the control system. The filter is capable of determining craft attitude based on feedback from orthogonally positioned gyroscopes and accelerometers.

An Access Control List is an ordered list of rules which specify the action to take for any packet which is tested and matched against it. The list is arranged in order of decreasing priority, therefore if a match is made on a particular rule the packet is either permitted or denied and no further rules are evaluated. When configuring firewall rules it is possible to specify varying levels of granularity when examining the fields of a packet header. The most basic form of checking is on the source Layer 3 address. However there are more complex forms of the rule which enables further fields to be checked. This paper investigates the effect on the performance of a router when using these complex rules. In particular it concentrates on the checking of the port number field in TCP/UDP. A specialized simulator was built to help understand the process undertaken by the router. There are results of the investigations and a recommendation on how to improve performance in certain areas.

Purpose. The purpose of image feature classification is to divide an image into several meaningful regions according to certain features, making these features the same or similar in a certain region but significantly different in different regions. In this paper, we will investigate the role of neural network and particle swarm optimization (PSO) in the image feature classification. Methodology. We propose the image feature classification method that combines PSO with neural network. BP neural network has been extensively applied in feature classification and it can classify specific objects or features through early learning, however, BP neural network algorithm also has many defects, including slow convergence speed and easiness to be trapped in local optimum. PSO optimized neural network fully exhibits its global search ability and parallel operation ability. Findings. Firstly, we take the gray image with specific object as the object to be segmented, study the samples with PSO neural network and get the training network. Secondly, we take the pixel matrix of the image as the input vector and put in the well-trained network for classification. Finally, the image feature classification can be realized. Originality. We made a study of image feature classification based on the particle swarm optimization neural network. We discussed the theory of image feature classification, basic principles of PSO and neural network. Practical value. We have also conducted the simulation experiment to confirm that the method suggested in this paper is a feasible one. We have proved that it has higher convergence speed and stronger robustness. Through the highly-efficient processing, this method can obtain important information and achieve excellent effect when used in the segmentation of the objects in complicated scenes.

Purpose. Creation of a mathematical model of conditions and factors of stability of the established motion of a machine unit whose working machine is a drum, permanently rotating around the horizontal axis, with a fluid fill of the chamber. Methodology. A filled drum is considered to be a system with permanent composition with variable inertial parameters whose variability is due to the redistribution at relative motion of masses of fluid fill of the chamber on the body of the drum. Based on the application of the principle of hardening of a mechanical system, the drum rotation equations take into account the whole mass of the fill, regardless of the nature of its interaction with the surface of the chamber. We employed methods of the mechanics of relative motion for the mathematical description of the undisturbed motion of the system. The principle of establishing a hierarchy of variables was applied. A hypothesis is accepted about proximity of the system's motion to the rotation with a slowly changing angular velocity. It is believed that dynamic and inertial pa- rameters of the filled drum are determined by the quasi-static dependences on the rotation velocity. We used a second-order Lagrange equation for a system with variable inertial parameters in order to determine the transitional motion. A direct Lyapunov method is applied to search for conditions of the motion stability. Findings. Dynamic and inertial parameters of the filled drum are formalized using differential equations of undisturbed steady and transitional rotation. We obtained a condition of asymptotic stability of the established motion of a tumbling mill machine unit. Instability factors of the system's motion are determined. Originality. Regularities of steady rotation of a drum mill are identified. It was established that factors of instability in the established, rotational around the horizontal axis, motion of the drum filled with a fluid medium, are the variations of variable inertial parameters - the axial moment of inertia and the moment of resistance of the fill to rotation. It is shown that the failure to comply with conditions of the motion stability could be caused by achieving the extreme negative values of derivatives from the inertial parameters of the inchamber fill by the angular velocity of drum rotation. Practical value. The developed mathematical model allows us to qualitatively determine conditions of steady rotational motion of the drum with a fluid fill of the chamber. Conditions for the occurrence of unstable motion have considerable practical significance because they cause self-excitation of auto-oscillations of the filled drum and determine improvement of effectiveness of grinding process in tumbling mills with traditional design solutions.

Let U be an open subset of a real, separable Banach space E, and denote by <$E OMEGA sub U> the set of all functions f, which take continuously values in U during a certain time interval <$E ]s(f),~ t(f)[>. The martingale problem is formulated for a drift term <$E phi> and a diffusion term Q both defined on <$E D sub U ~=~{(t,f)~:~f~<174>~ OMEGA sub U~{roman and}~t~<174>~] s(f), ~t(f)[>}. We prove that under certain local conditions on <$E phi> and Q there exists a unique solution of this martingale problem up to a stopping time <$E tau sub U>, which can be interpreted as an explosion time. The path process constitutes a strong Markov process with life time <$E tau sub U>. The main idea of the proof is to put unique local solutions together. The explosion time is obtained explicitly as a supremum of a sequence of comparatively simple and natural stopping times.