Nonlinear Oscillatory Dynamics of the Hardening of Calcium Phosphate Bone Cements

Here we report on the nonlinear, oscillatory dynamics detected in the evolution of phase composition during the setting of different calcium phosphate cements, two of which evolved toward brushite and one toward hydroxyapatite as the final product. Whereas both brushite-forming cements contained iondoped b-tricalcium phosphate as the initial phase, the zinc-containing one yielded scholzite as an additional phase during setting and the oscillations between these two products were pronounced throughout the entire 80 h setting period, long after the hardening processes was over from the mechanical standpoint. Oscillations in the copper-containing system involved the amount of brushite as the main product of the hardening reaction and they progressed faster toward an equilibrium point than in the zinc-containing system. Initially detected with the use of in situ energy-dispersive X-ray diffractometry, the oscillations were confirmed with a sufficient level of temporal matching in an in situ Fourier transform infrared spectroscopic analysis. The kinetic reaction analysis based on the Johnson– Mehl–Avrami–Kolmogorov model indicated an edge-controlled nucleation mechanism for brushite. The hydroxyapatite-forming cement comprised gelatin as an additional phase with a role of slowing down diffusion and allowing the detection of otherwise rapid oscillations in crystallinity and in the amount of the apatitic phase on the timescale of minutes. A number of possible causes for these dynamic instabilities were discussed. The classical chemical oscillatory model should not apply to these systems unless in combination with less exotic mechanisms of physicochemical nature. One possibility is that the variations in viscosity, directly affecting diffusion and nucleation rates and accompanying growth and transformation from the lower to the higher interfacial energy per the Ostwald–Lussac rule, are responsible for the oscillatory dynamics. The conception of bone replacement materials and tissue engineering constructs capable of engaging in the dynamics of integration with the natural tissues in compliance with this oscillatory nature may open a new avenue for the future of this type of medical devices. To succeed in this goal, the mechanism of these and similar instabilities must be better understood

Valence State Ce(Yb), Electron Structure and Physical Properties of New Ternary Intermetallic Compounds

High-energy spectroscopy (XES, XAS and XPS) has been used to study the electron structure of the investigated new ternary intermetallic compounds. In recent years there has been a continually increasing interest in investigation of ternary compounds with crystallize in the YNi9Si2, CeGa2Al2, Yb2Fe4Si9, ThMn12 and AlB2, which have a large variety of ground state properties. LIII -absorption spectra Ce(Yb) in ternary compounds were obtained at 80K and 300K using a tube spectrometer. The mixed valence state of Ce(Yb) was obtained in the investigation compounds. The measurements were carried out both with classical methods as well with the Mossbauer effect in order to establish parameters of the hyperfine interactions (only for confirm Fe atoms compounds). The calculations of electron energy bands E(k) and partial DOS for compounds new R.E.M2X2 were performed by the semi relativistic linear muffin-tin orbital method without considerations of spin-orbit interactions A satisfactory agreement between theoretical and experimental data is achieved

Nanostructured relief to orient liquid crystals materials

Electrooptical nematic liquid crystal (LC) cells, which can be used as laser switching devices, electrically and optically addressed spatial light modulators, and analogs of display elements, mostly operate in S and T configurations, which realize a planar orientation of the LC mesophase on the aligning substrate surface. However, the solution of some problems, where the initial black field is necessary for the regime of light transmission through the cell structure, requires a homeotropic alignment of LC molecules on the substrate. In the present paper the possibility of obtaining homeotropic orientation in thin film nematic liquid crystal cells using carbon nanotubes is considered. The results of this investigation can be used to develop optical elements for displays with vertical orientations of NLC molecules (MVA-display technology)

Cell-selective toxicity of hydroxyapatite-chitosan oligosaccharide lactate particles loaded with a steroid cancer inhibitor

The applicative potential of synthetic calcium phosphates, especially hydroxyapatite (HAp), has become intensely broadened in the past 10 years, from bone tissue engineering to multiple other fields of biomedicine. Hybrid systems based on nano hydroxyapatites (HAp) are the subject of numerous studies in preventive and regenerative medicine. HAp nanoparticles coated with bioresorbable polymers have been successfully used as fillers, carriers of antibiotics, vitamins and stem cells in bone tissue engineering, etc. In this study we utilize an emulsification process and freeze drying to load the hybrid system made of nano HAp particles coated with chitosan oligosaccharide lactate (ChOSL) with two different but similar steroid derivatives: 3β-hydroxy- 16-hydroxymino-androst-5-ene-17-one (A), C19H27NO3 and 3β, 17β-dihydroxy-16-hydroxyminoandrost- 5-ene (B), C19H29NO3. The cell-selective toxicity of HAp particles coated with of A- or B-loaded ChOSL was examined simultaneously on the following cell lines: human breast carcinoma (MCF-7, MDA-MB-231), human lung carcinoma (A549) and human lung fibroblasts (MRC-5), using dye exclusion (DET) and MTT assays. 1H NMR, 13C NMR and high-resolution time-of-flight mass spectrometry (MS) techniques confirmed the intact structure of the derivatives A or B. FT-IR, XRD, DTA, TGA and DSC techniques confirmed the drug loading process of steroide (A or B) in core–shell particles based on nano hydroxyapatite. Atomic force microscopy and particle size analyses were used to confirm that the particles were spherical with sizes between 80 and 240 nm. The measured values of electrokinetic parameters (zeta potential, electrophoretic mobility and conductivity) were significantly different for the steroid free carrier (HAp/ChOLS) and A- or B-loaded ChOSL. The value of the topological molecular polar surface area (TPSA, the sum of the surfaces of polar atoms and groups in the molecule), were also different for drug free carrier and A- or BHAp/ ChOLS. Highly selective anticancer activity was noted towards breast cancer cells (MDAMB- 231) by B-loaded HAp/ChOLS. DET testing after 48 hours (after incubation and recovery) of the treatment with A-HAp/ChOSL and B-HAp/ChOSL particles showed a high viability of healthy cells (over 80%). The lowest viability was found in MDA-MB-231 cancer cells treated with B-HAp/ChOSL (28%). The obtained results of the DET and MTT tests showed that the particles of A-HAp/ChOLS exhibited nearly four-fold greater cytotoxicity towards breast cancer cells (MDA-MB-231) than towards healthy cells (MRC-5). B-HAp/ChOSL particles exhibited nearly six times greater cytotoxicity to all breast cancer cells than to healthy ones

Electron structure, valense state, X-ray spectra and surface morfhologies of the new CeM2P2 (M=Fe, Co, Ni) compounds

High-energy spectroscopy has been used to study the electronic structure and valence state of new ternary intermetallic CeM2P2 (M=Fe, Co, Ni) compounds which crystallize in the ThCr2Si2 types. The calculations of electron energy bands E(k) and partial DOS for compounds were performed by the semi- relativistic linear muffin-tin orbital method without considerations of spin-orbit interactions. Effective filling numbers of electrons in different bands of components in CeM2P2 (M=Fe, Co, Ni) compounds have been calculated. Analysis of the results of calculations showed that the degree of occupation of spd-valence orbital of components varies and differs considerably from of external electrons in isolated atoms. The occupancy of d-orbital of M in the CeM2P2 compounds was shown to be significantly larger than in an isolated state. The electron configuration of P in compounds can be described as s1.4p2.8. LIII – absorption spectra Ce in the ternary CeM2P2 (M=Fe, Co, Ni) compounds were obtained at 78 K and 300 K using a tube spectrometer equipped with an RKD -01 coordinate detector. The mixed valence state of Ce was obtained in the investigated compounds. Surface morphologies CeM2P2 (M=Fe, Co, Ni) compounds are investigated by scanning tunneling microscopy (NT-MDT). The range scanning was 100 um x 100 um and 2 um x 2 um. The surface topography, distribution of grain diameter and area were obtained. The distribution of grain diameter and area of the CeM2P2 (M=Fe, Co, Ni) compounds is established. The picture of the distribution of the stiffness of the samples (amplitude and phase fluctuations) is obtained

Dynamic Mechanical Properties of Aramid Fabrics Impregnated with Carbon Nanotube/Poly (Vinyl Butyral)/Ethanol Solution

In this study six samples of polyurethane/p-aramid multiaxial fabric forms (Colon fabrics) were coated with 10 wt.% poly (vinyl butyral) (PVB)/ethanol solution with the addition of multiwalled carbon nanotubes (MWCNT). The solution was impregnated on both sides of each of the fabrics. All composite samples consisted of four layers of the impregnated fabrics. The MWCNT/PVB content was 0, 0.1 and 1 wt.%. The three samples of the fabrics with different MWCNT/PVB content were coated with γ-aminopropyltriethoxysilane (AMEO silane)/ethanol solution due to the surface modification. The mechanical properties of the prepared composite samples were studied by dynamic mechanical analysis (DMA). The 60% increase in storage modulus was achieved by addition of MWCNT and impregnation of aramid fabrics with AMEO silane. The pristine multiwalled carbon nanotubes (MWCNT) were introduced in order to enhance additionally the mechanical properties of the materials for ballistic protection

Influence of the nanostructure on the surface and bulk physical properties of materials

Fullerenes, nanotubes, quantum dots have been considered as effective sensitizers to modify both the spectral, optical, nonlinear optical features, dynamic and polarization characteristics, as well as mechanical properties of the organic and inorganic materials. Laser, spectroscopy, mass-spectroscopy, nuclear magnetic resonance methods have been apply to support the change in the physical properties of the new nanocomposites. The extending of the nanocomposites applications area has been considered

Nanostructured materials for optoelectronic applications

New way to improve the surface properties of the inorganic and organic materials via nanotubes treatment process has been shown. It has been testified that the surface mechanical hardness of the MgF2, LiF, etc. materials can be increased up to 3-10 times under the conditions of the spectral range keeping. Some simple model to explain the results has been discussed. As an additional, some features of transparent conducting ITO contacts modified with surface electromagnetic waves have been found. The data presented in the current paper testified that these nano-objects-optimized materials could be used as new elements and new laser window for the UV and IR spectral range