Encapsulation of DNA by cationic diblock copolymer vesicles

Encapsulation of dsDNA fragments (contour length 54 nm) by the cationic diblock copolymer poly(butadiene-b-N-methyl 4-vinyl pyridinium) [PBd-b-P4VPQ] has been studied with phase contrast, polarized light, and fluorescence microscopy, as well as scanning electron microscopy. Encapsulation was achieved with a single emulsion technique. For this purpose, an aqueous DNA solution is emulsified in an organic solvent (toluene) and stabilized by the amphiphilic diblock copolymer. The PBd block forms an interfacial brush, whereas the cationic P4VPQ block complexes with DNA. A subsequent change of the quality of the organic solvent results in a collapse of the PBd brush and the formation of a capsule. Inside the capsules, the DNA is compacted as shown by the appearance of birefringent textures under crossed polarizers and the increase in fluorescence intensity of labeled DNA. The capsules can also be dispersed in aqueous medium to form vesicles, provided they are stabilized with an osmotic agent (polyethylene glycol) in the external phase. It is shown that the DNA is released from the vesicles once the osmotic pressure drops below 105 N/m2 or if the ionic strength of the supporting medium exceeds 0.1 M. The method has also proven to be efficient to encapsulate pUC18 plasmid in sub-micron sized vesicles and the general applicability of the method has been demonstrated by the preparation of the charge inverse system: cationic poly(ethylene imine) encapsulated by the anionic diblock poly(styrene-b-acrylic acid).Comment: 35 pages, 11 figures, accepted for publication in Langmui

Influence of a mutltistrand cable design on its quench development process and stability

The quench development process was studied with two six-strand superconducting cable samples with insulated strands and different cabling design. One sample was the traditional ‘six-around-one’ cable, the other was of the ‘round-braid’ type. Quench was initiated by a heating pulse applied to a single strand. A significant difference was observed in the current redistribution among strands due to the different cabling designs. It has an important influence on the stability of multistrand cables. A new concept of the ‘single-strand stability’ was proposed and corresponding stability criteria were offered. A possible way to improve cable stability by using special cabling design is discussed

Simulation of oscillation dynamics of mechanical system with the electrorheological shock-absorber

The paper presents the development of mathematical model of oscillating system by taking into account electrorheological (ER) characteristics. Characteristics of the ER shock-absorber (dependences of force on value of control electric signal considering shock-absorber geometry, rod displacement, rheological properties of ER fluid) are calculated. Comparison of simulation results of shock-absorber characteristics with experimental findings is performed. Analysis of calculated relations of amplitudes of output and input signals depending on value of a control electric signal is carried ou

Simulation of Performance Characteristics of a Magnetorheological Shock-Absorber at the Dependence of Rheological Properties from the Magnetic Field

The mathematical model of a magnetorheological shock-absorber taking into account of the dependence of rheological properties from the magnetic field is developed. Performance characteristics of the MR shock-absorber (dependences of force on value of control electric signal taking into account of shock-absorber geometry, rod displacement, rheological properties of MR fluid) are calculated. The analysis of influence of control electric signal value on MR shock-absorber performance characteristics depending on amplitudes and frequencies of piston movement is carried out

Electrosensitive glue for vibrotesting of radioelectronic industry items

The possibility of using electrocontrolled glue (ER glue) for fixing radioelectronic industry items during their vibrotesting is discussed. The schemes are presented for fixing items of different materials and shapes to the electrodes of the basic surface of the fixing device. The impact of technological factors is demonstrated to enable us to obtain an increase in the specific fixing force sufficient for mounting the items in order to conduct experiments in the required range of vibro-acceleration

МНОГОЧАСТОТНЫЕ АЛГОРИТМЫ ОПРЕДЕЛЕНИЯ ВЛАГОСОДЕРЖАНИЯ ЖИДКИХ ЭМУЛЬСИЙ МЕТОДОМ РЕЗОНАСНОЙ ДИЭЛЬКОМЕТРИИ

Purpose. The main attention is paid to the development and investigation of multifrequency algorithms for the realization of the method of resonance dielcometric measurement of the humidity of emulsions of the type «nonpolar liquid dielectric-water». Multifrequency algorithms take into account the problem of «uncertainty of varieties» and increase the sensitivity of the dielcometric method. Methodology. Multifrequency algorithms are proposed to solve the problem of «uncertainty of varieties» and improve the metrological characteristics of the resonance dielcometric method. The essence of the algorithms is to use a mathematical model of the emulsion and to determine the permittivity of the dehydrated liquid and the emulsion. The task of developing algorithms is to determine and take into account the influence of the parasitic electrical capacitance of the measuring oscillator and the measuring transducer. The essence of the method consists in alternately determining the resonance frequency of the oscillatory circuit with various configurations, which allows to take into account errors from parasitic parameters. The problem of «uncertainty of varieties» is formulated and solved. The metrological characteristics of the resonance dielcometric method are determined using algorithms. Results. Frequency domains of application of mathematical model of an emulsion are defined. An algorithm in a general form with four frequencies suitable for practical implementation in dielcometric resonance measurements is developed. Partial algorithms with three and two frequencies are developed. The systematic values of simulation errors in the emulsion in the microwave range are determined. Generalized metrological characteristics are obtained. The ways of increasing the sensitivity of the dielcometric method are determined. The problem of «uncertainty of varieties» was solved. Experimental data on determination of humidity for the developed algorithms are obtained. The value of the volumetric moisture in the transformer oil was measured. Originality. New multifrequency algorithms for determining the moisture content by the resonance dielcometric method have been proposed, investigated and practically realized. A generalized metrological characteristic for an algorithm with four frequencies is obtained. Metrological characteristics of algorithms for three and two frequencies are obtained. The problem of «uncertainty of varieties» was solved. Recommendations for increasing the sensitivity of dielcometric resonance moisture meters are developed and implemented. Practical value. The results of this work allow to solve the problem of «variability of varieties», increase sensitivity and accurately determine the moisture content in most nonpolar liquid dielectrics to a value of 10-5. This is applicable in a large field of electrical engineering, machine building, oil refining and the chemical industry.Предложены многочастотные алгоритмы определения влагосодержания эмульсии типа: «неполярный жидкий диэлектрик – вода» методом резонансной диэлькометрии. Использована математическая модель эмульсии с представлением воды в виде идеально проводящих сфер. Определены частотные области применимости модели в ВЧ и СВЧ диапазонах. В СВЧ диапазоне определены величины систематических погрешностей модели. Для решения проблемы «сортовой неопределенности» и улучшения метрологических характеристик резонансного диэлькометрического метода разработан четырехчастотный алгоритм, являющийся обобщенным видом трех- и двухчастотных алгоритмов. Определена обобщенная метрологическая характеристика четырехчастотного алгоритма и его предельные характеристики. Получены метрологические характеристики для трех- и двухчастотных алгоритмов. Проведен анализ погрешностей и корректности теоретических исследований путем сравнения их результатов с экспериментальными данными для ВЧ и СВЧ диапазонов

MULTIFREQUENCY ALGORITHMS FOR DETERMINING THE MOISTURE CONTENT OF LIQUID EMULSIONS BY THE METHOD OF RESONANCE DIELCOMETRY

Purpose. The main attention is paid to the development and investigation of multifrequency algorithms for the realization of the method of resonance dielcometric measurement of the humidity of emulsions of the type «nonpolar liquid dielectric-water». Multifrequency algorithms take into account the problem of «uncertainty of varieties» and increase the sensitivity of the dielcometric method. Methodology. Multifrequency algorithms are proposed to solve the problem of «uncertainty of varieties» and improve the metrological characteristics of the resonance dielcometric method. The essence of the algorithms is to use a mathematical model of the emulsion and to determine the permittivity of the dehydrated liquid and the emulsion. The task of developing algorithms is to determine and take into account the influence of the parasitic electrical capacitance of the measuring oscillator and the measuring transducer. The essence of the method consists in alternately determining the resonance frequency of the oscillatory circuit with various configurations, which allows to take into account errors from parasitic parameters. The problem of «uncertainty of varieties» is formulated and solved. The metrological characteristics of the resonance dielcometric method are determined using algorithms. Results. Frequency domains of application of mathematical model of an emulsion are defined. An algorithm in a general form with four frequencies suitable for practical implementation in dielcometric resonance measurements is developed. Partial algorithms with three and two frequencies are developed. The systematic values of simulation errors in the emulsion in the microwave range are determined. Generalized metrological characteristics are obtained. The ways of increasing the sensitivity of the dielcometric method are determined. The problem of «uncertainty of varieties» was solved. Experimental data on determination of humidity for the developed algorithms are obtained. The value of the volumetric moisture in the transformer oil was measured. Originality. New multifrequency algorithms for determining the moisture content by the resonance dielcometric method have been proposed, investigated and practically realized. A generalized metrological characteristic for an algorithm with four frequencies is obtained. Metrological characteristics of algorithms for three and two frequencies are obtained. The problem of «uncertainty of varieties» was solved. Recommendations for increasing the sensitivity of dielcometric resonance moisture meters are developed and implemented. Practical value. The results of this work allow to solve the problem of «variability of varieties», increase sensitivity and accurately determine the moisture content in most nonpolar liquid dielectrics to a value of 10-5. This is applicable in a large field of electrical engineering, machine building, oil refining and the chemical industry

Simulation of oscillation dynamics of vibroprotective system with the electrorheological shock-absorber

The paper presents development of a mathematical model of a three-mass oscillating vibroprotective system with electrorheological (ER) shock-absorber by taking into account influences of temperature and electric field. Performance characteristics of the ER shockabsorber are established including dependences of force on rod displacement for different absorber geometry, rheological properties of ER fluid and magnitudes of temperature and electric field. This research work also provides comparison of simulation results of ER vibroprotective system during its linear movement through road profile “the sleeping policeman” in time domain. Amplitude-frequency characteristics of the vibroprotective system with ER shock-absorber are determined as function of electric field strength and temperature

Calculations of electrical fixing device for vibrotesting of electronic components

The description of the device with the electrical sensitive glue to fix components of electronic devices (capacitors, resistors, chips) at their trials on harmonic and shock loads with the aid of shaker table is presented. Based on the polarization forces of interaction of the filler particles in the structure of the electrical glue we have performed a simulation and calculation of the limiting values of fixing forces of the component with the electrode of the mounting devices. Parameters of the electric field corresponding to the utmost full transmission of vibrations to the component are determined