Polystyrene-based nanocomposites with different fillers: fabrication and mechanical properties

The paper presents a comprehensive analysis of elastic properties of polystyrene-based nanocomposites filled with different types of inclusions: small spherical particles (SiO2 and Al2O3), alumosilicates (montmorillonite, halloysite natural tubules and Mica) and carbon nanofillers (carbon black and multi-walled carbon nanotubes). Composites were fabricated by melt technology. The analysis of composite melts showed that the introduction of Montmorillonite, Multi-walled carbon nanotubes, and Al2O3 particles provided an increase in melt viscosity by an average of 2 to 5 orders of magnitude over the pure polystyrene. Block samples of composites with different filler concentrations were prepared, and their linear and nonlinear elastic properties were studied. The introduction of more rigid particles led to a more profound increase in the elastic modulus of the composite, with the highest rise of about 80% obtained with carbon fillers. Carbon black particles provided also an enhanced strength at break of about 20% higher than that of pure polystyrene. The nonlinear elastic moduli of composites were shown to be more sensitive to addition of filler particles to the polymer matrix than the linear ones. The nonlinearity coefficient $\beta$ comprising the combination of linear and nonlinear elastic moduli of a material demonstrated considerable changes correlating with changes of the Young's modulus. The absolute value of $\beta$ showed rise in 1.5-1.6 times in the CB- and HNT-containing composites as compared to that of pure PS. The changes in nonlinear elasticity of fabricated composites were compared with measurements of the parameters of bulk nonlinear strain waves in them. Variations of wave velocity and decay decrement correlated with observed enhancement of materials nonlinearity

МЕТОДОЛОГІЧНІ АСПЕКТИ ЗАСТОСУВАННЯ АВТОМАТИЗОВАНИХ НАВЧАЛЬНИХ СИСТЕМ У ВИЩИХ МЕДИЧНИХ НАВЧАЛЬНИХ ЗАКЛАДАХ В УМОВАХ КРЕДИТНО-МОДУЛЬНОЇ СИСТЕМИ

Methodological approaches to ATS adoption in educational process of higher medical educational establishments in credit-module system were grounded in the article. Methodological peculiarities of introduction of ATS RATOS on the basis of 5 year use experience in Zaporozhye State Medical University and in National Medical University named after A.A.Bogomolets are considered. Peculiarities and functions of ATS in new conditions are found out and specified, introduction stages are disclosed.В статье обоснованы методологические подходы внедрения автоматизированных обучающих систем (АОС) в образовательный процесс высших медицинских заведений в условиях кредитно-модульной системы. Рассмотрены методические особенности внедрения АОС RATOS® на основе пятилетнего опыта ее использования в Запорожском государственном медицинском университете и Национальном медицинском университете им. А.А. Богомольца. Определены и уточнены особенности и функции АОС  в новых условиях, показаны этапы её внедрения.У статті обґрунтовані методологічні підходи щодо впровадження  автоматизованих навчальних систем (АНС) в освітній процес вищих медичних навчальних закладів за умов кредитно-модульної системи.  Розглянуто методичні особливості впровадження АНС RATOS на базі  п’ятирічного досвіду її застосування у Запорізькому державному медичному  університеті та Національному медичному університеті імені О.О. Богомольця.  З’ясовано та уточнено особливості і функції АНС в нових умовах, розкрито етапи її впровадження

Morphology and toughness of coextruded PS/PMMA multilayers

The micromechanical behaviour of multilayered tapes made of two brittle incompatible amorphous polymers PS and PMMA was studied by means of an optical and a High Voltage Electron Microscope (HVEM). Microlayers of PS and PMMA were coextruded with varying number of layers: 64, 512 and 4096 layers. Mechanical properties of the PS/PMMA tapes were also examined. An increase in layer numbers was found to lead to a decrease in layer thickness that, in turn, resulted in: a) formation of thicker and longer crazes and, therefore, increased volume of the material involved in the plastic deformation; b) a noticeable increase in strength and strain at break (i.e. of toughness) of the samples. Enhanced toughness of the multilayered tapes is accounted for by massive cooperating crazing and yielding of both PS and PMMA phases

Morphology and temperature phase transitions in alpha,omega-alkanediols with different chain lengths

A comparative analysis of phase transitions in diols with various chain lengths [(CH2)(44)(OH)(2) and (CH2)(22)(OH)(2)] and changes in their absorption spectra with temperature have been investigated by DSC and FTIR. Analysis of the DSC data has led to the conclusion that the low-temperature phase transition of (CH2)22(OH)2 in a solid state (Ts-s = 367.1 K) is a phase transition of the first order, while the high-temperature phase transition (T-m = 376.3 K) is of the second order, i.e., a transition of the order-disorder type. Splitting of the IR absorption bands into doublets at 720-730 cm(-1) and 1463-1473 cm(-1) indicates that crystalline subcells in the lamellae of both diols are orthorhombic lattices with the parameters typical of hydrocarbons. IR spectra showed that at the phase transition temperature Ts-s transformation of an orthorhombic subcell into a hexagonal one occurs. This type of molecular chain packing remains the same up to the melting temperature T-m. In a (CH2)44(OH)2 diol, the ortho-hexagonal subcell transition occurs only at the melting temperature (390.0 K). The wide IR band in the region from 3000 cm(-1) to 3600 cm(-1) shows that end hydroxyl groups of diol molecules form, on the surfaces of lamellar crystals, long (polymer) regular sequences consisting of intermolecular hydrogen bonds

Ultra-small-angle X-ray Scattering Study of PET/PC Nanolayers relating to AFM results

146 serial determinations of spontaneous and phytohemagglutinin-induced lymphocyte transformation as measured by tritiated thymidine incorporation, were performed in 24 healthy individuals. 9 persons were studied intensively during a mean period of 40 days and the other 15 underwent random investigations during a period up to 10 months. Transient episodes of significant decreased lymphocyte transformation were revealed in 14 persons (58.4%) with regard to the spontaneous blastogenesis and in 11 subjects (45.8%) with regard to PHA-induced reactivity. The occurrence of the decreased values in PHA responsiveness was significantly higher in the intensively studied group compared to the randomly investigated one (p = 0.001). The probability of detecting one low PHA-related response in a normal subject was 11%. In only half of the cultures with low spontaneous blastogenic response did a simultaneous decrease in PHA-induced lymphocyte transformation occur. In addition to the currently used stimulation index, a new index termed the Blastogenic Cumulative Index is proposed. It is defined as the sum of the logarithms of the dpm values of the spontaneous and the PHA induced lymphocyte transformation. The CI is suggested to describe lymphocyte blastogenic function more accurately, and due to its simplicity warrents further study. Other indices for lymphocyte blastogenesis determination are discussed