336 research outputs found
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 and Structure Functions in Low Region with the IHEP-JINR Neutrino Detector
The isoscalar structure functions and are measured as functions
of averaged over all 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 structure function provides
MeV under the assumption of QCD
validity in the region of low . The corresponding value of the strong
interaction constant 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
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