The Study of the Alginate / Hydroxyapatite Composites Structural Properties

This paper describes the synthesis of sodium alginate (Alg) / hydroxyapatite (HA) composites and the influence of the presence of Alg on HA crystallization. Such composites become rather widespread in recent years, and are used in medicine generally for the controlled drug delivery [1‑3]. In one’s case, Alg is used as the functional and cost-effective replacement of the collagen for the creation of implants similar to the natural bone [4]. It was shown that the presence of Alg and the increase of its concentration leads to the decrease of the HA crystallinity thus providing an ability to control its levels in the resulting product. The FTIR studies confirm the incorporation of Alg in the Alg / HA composite structure

Magnetite-polymer Nanoparticles: Structure and Properties

The paper describes synthesis of magnetite-alginate composites. The main feature of such biomaterials is the simultaneous formation of magnetite nanoparticles inside the alginate matrix. Obtained samples were characterized by X-ray diffraction and transmission electron microscopy. In several samples the secondary phase of ammonium chloride was observed. The average crystallite sizes of magnetite phase are about 13 nm. The addition of alginate leads to the decrease of microstrains in [h k 0] direction

The Study of the Influence of Static Magnetic Field on Brushite Crystallization in the Presence of Magnesium

The paper describes the influence of the imposition of static magnetic field on brushite crystallization. Two different configurations of the magnetic field were used. The flasks with the precipitates were placed near the different poles. It was shown that changing the magnetic field configuration and positioning the samples in proximity to north or south poles can greatly affect their crystallinity and texture with most of them having the preferred orientation along the b-axis according to the X-Ray diffraction data. The imposition of the magnetic field also influences the microstrain ratio decreasing it significantly. It was also verified [1] that the Mg substrate availability decreases the crystallinity of DCPD. The micrographs of the nanoparticles with the different magnifications were obtained by the transmission electron microscopy (TEM). The comparative analysis of the electron microscopy data correlates with the XRD data. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3546

Structural Properties of the Nanocrystallized Magnetite of Different Syntheses

Transmission electron microscopy (TEM) with electronic diffraction and X-ray diffraction (XRD) was used to study structural features of nanosized magnetite Fe3O4, which was synthesized using polymeric matrices (polysaccharide chitosan, at alias). From the received data it was revealed that growth inhibition and size stabilization of Fe3O4 nanoparticles were strongly affected by polysaccharide matrix. It was also observed that directional size decrease of Fe3O4 nanoparticles was accompanied by the increasing defectiveness of crystal lattice and decreasing unit cell size. The effectiveness of complementary use of both TEM with electronic diffraction and XRD techniques for structural and substructural parameters determination while studying magnetite nanosized particles synthesized in polysaccharide matrices is shown in this paper. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3545

Structural Properties of the Nanocrystallized Magnetite of Different Syntheses

Transmission electron microscopy (TEM) with electronic diffraction and X-ray diffraction (XRD) was used to study structural features of nanosized magnetite Fe3O4, which was synthesized using polymeric matrices (polysaccharide chitosan, at alias). From the received data it was revealed that growth inhibition and size stabilization of Fe3O4 nanoparticles were strongly affected by polysaccharide matrix. It was also observed that directional size decrease of Fe3O4 nanoparticles was accompanied by the increasing defectiveness of crystal lattice and decreasing unit cell size. The effectiveness of complementary use of both TEM with electronic diffraction and XRD techniques for structural and substructural parameters determination while studying magnetite nanosized particles synthesized in polysaccharide matrices is shown in this paper. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3545

Biphasic Calcium Phosphate Composite for Biomedical Applications

The paper describes the preparation of the biphasic (hydroxyapatite (HA) and tricalcium phosphate (TCP)) nanostructured calcium phosphate composite. The product was chemically synthesized from the solution which contained calcium acetate Са(СН3СОО)2 (0,167 mМ), sodium dihydrogen phosphate NaH2PO4 (0,1 mМ), sodium hydrocarbonate NaHCO3 (0,02 mM). The calcium phosphate composite was formed at pH=11 with and without the addition of carbonate ions. The samples were analyzed using X-Ray diffraction after the heat treatment at 900C for 1 h. The derived material contained HA and TCP phases with their contents change depending on the concentration of the carbonate ions in the solution. The mean crystallite size of the HA phase in (121) plane is 12 – 14 nm. Further studies will be directed to the using of the derived composite for the biomedical applications. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3544

Magnetite-polymer Nanoparticles: Structure and Properties

The paper describes synthesis of magnetite-alginate composites. The main feature of such biomaterials is the simultaneous formation of magnetite nanoparticles inside the alginate matrix. Obtained samples were characterized by X-ray diffraction and transmission electron microscopy. In several samples the secondary phase of ammonium chloride was observed. The average crystallite sizes of magnetite phase are about 13 nm. The addition of alginate leads to the decrease of microstrains in [h k 0] direction

An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles

The extreme solar and SEP event of 20 January 2005 is analyzed from two perspectives. Firstly, we study features of the main phase of the flare, when the strongest emissions from microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin of SEPs arriving at Earth, i.e., acceleration in flares, or shocks ahead of CMEs. All emissions from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just above sunspot umbrae. A huge radio burst with a frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic electrons in strong magnetic fields. Thus, protons and electrons responsible for flare emissions during its main phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the GLE, and highest-energy gamma-rays identified with pi^0-decay emission, are similar and correspond in time. The origin of the pi^0-decay gamma-rays is argued to be the same as that of lower energy emissions. We estimate the sky-plane speed of the CME to be 2000-2600 km/s, i.e., high, but of the same order as preceding non-GLE-related CMEs from the same active region. Hence, the flare itself rather than the CME appears to determine the extreme nature of this event. We conclude that the acceleration, at least, to sub-relativistic energies, of electrons and protons, responsible for both the flare emissions and the leading spike of SEP/GLE by 07 UT, are likely to have occurred simultaneously within the flare region. We do not rule out a probable contribution from particles accelerated in the CME-driven shock for the leading GLE spike, which seemed to dominate later on.Comment: 34 pages, 14 Postscript figures. Solar Physics, accepted. A typo corrected. The original publication is available at http://www.springerlink.co

Chemostratigraphy of Neoproterozoic carbonates: implications for 'blind dating'

The delta C-13(carb) and Sr-87/Sr-86 secular variations in Neoproteozoic seawater have been used for the purpose of 'isotope stratigraphy' but there are a number of problems that can preclude its routine use. In particular, it cannot be used with confidence for 'blind dating'. The compilation of isotopic data on carbonate rocks reveals a high level of inconsistency between various carbon isotope age curves constructed for Neoproteozoic seawater, caused by a relatively high frequency of both global and local delta C-13(carb) fluctuations combined with few reliable age determinations. Further complication is caused by the unresolved problem as to whether two or four glaciations, and associated negative delta C-13(carb) excursions, can be reliably documented. Carbon isotope stratigraphy cannot be used alone for geological correlation and 'blind dating'. Strontium isotope stratigraphy is a more reliable and precise tool for stratigraphic correlations and indirect age determinations. Combining strontium and carbon isotope stratigraphy, several discrete ages within the 590-544 Myr interval, and two age-groups at 660-610 and 740-690 Myr can be resolved

Measurement of xF3xF_3 and F2F_2 Structure Functions in Low Q2Q^2 Region with the IHEP-JINR Neutrino Detector

The isoscalar structure functions $xF_3$ and $F_2$ are measured as functions of $x$ averaged over all $Q^2$ permissible for the range of 6 to 28 GeV of incident neutrino (anti-neutrino) energy at the IHEP-JINR Neutrino Detector. The QCD analysis of $xF_3$ structure function provides $\Lambda_{\bar{MS}}^{(4)} = (411 \pm 200)$ MeV under the assumption of QCD validity in the region of low $Q^2$. The corresponding value of the strong interaction constant $\alpha_S (M_Z) = 0.123^{+0.010}_{-0.013}$ agrees with the recent result of the CCFR collaboration and with the combined LEP/SLC result.Comment: 11 pages, 1 Postscript figure, LaTeX. Talk given at the 7th International Workshop on Deep Inelastic Scattering and QCD (DIS 99), Zeuthen, Germany, 19-23 Apr 199