Ph.D. in Materials Science, 2003, Washington State University, Pullman,
WA
Abstracts of
peer-reviewed articles published in referred journals and conference
proceedings
Abstracts
of Journal Articles
1.
Kalita, S.J., Bhatt, H., and Dhamne, A., 2006.
MgO-Na2O-P2O5-based Sintering additives for
Tricalcium Phosphate Bioceramics. Journal
of the American Ceramic Society, 89 [3] 875–881, 2006. DOI: 10.1111/j.1551-2916.2005.00854.x
Effects of MgO-Na2O-P2O5-based
sintering additives on densification, microstructure, hardness, compression
strength and biodegradability of beta-tricalcium phosphate (b-TCP) ceramics were studied. Three additive compositions were prepared and
introduced into b-TCP. Uniaxially compacted ceramic structures,
sintered at 1250oC in air, were characterized. SEM was used to study
the microstructure. X-ray diffraction technique was used for phase analysis.
Results showed that these additives modified the microstructure and improved
the sintered density and mechanical properties. An increase of 9% in density,
40% in hardness and 38% in compression strength were achieved. Biodegradation
analysis revealed that these additives could tailor the rate of resorption and hardness
degradation of b-TCP.
Manuscript No. 20544. Received May 9,
2005; approved October 26, 2005. r 2006 The American Ceramic Society
2.
Somani, V., and Kalita, S.J., 2006. Synthesis and Characterization of
Nanocrystalline Barium Strontium Titanate Power via Sol-Gel Processing. Journal
of Electroceramics DOI
10.1007/s10832-007-9008-7 (Received: 16 May 2005 / Accepted: 23 May 2006,
Published February 2007)
Barium Strontium
Titanate (BST) solid solution is a strong candidate material for application in
tunable ferroelectric devices. In this
research, we have synthesized and characterized nanocrystalline BST (Ba0.7Sr0.3TiO3)
powder with average particle-diameter of 15 nm through a simple sol-gel
process, using barium acetate, strontium acetate and titanium isopropoxide as
the precursors. In this process,
stoichiometric proportions of barium acetate and strontium acetate were
dissolved in acetic acid followed by refluxing, and addition of titanium (IV)
isopropoxide to form BST gel. The gel
was analyzed using Differential Scanning Calorimetry (DSC)
and Thermal Gravimetric Analysis (TGA).
The as-formed gel was dried at 200ºC and then calcined in the
temperature range of 400ºC to 800ºC for crystallization. Phase evolution during calcination was
studied using X-ray diffraction (XRD) technique. Particle size, morphology and the lattice fringes
of the calcined powder were characterized by high-resolution transmission
electron microscopy (HR-TEM). To study
the effects of sintering on BST nanopowder, green ceramic specimens were
prepared by uniaxial compaction and then sintered at 950-1100ºC under
atmospheric conditions. Sintered
specimens were analyzed for phase composition, grain size and geometric bulk
density. Keywords: Barium Strontium
Titanate. Nanopowder-synthesis. Nano-electroceramics. Sintering . Sol-gel. © Springer
Science + Business Media, LLC 2007
3.
Qiu, S., and Kalita, S.J., 2006. Synthesis, processing and characterization of
nanocrystalline titanium dioxide, Materials
Science and Engineering A, 435-436 (2006), pages 327-32. Available online at www.sciencedirect.com) Received 5
January 2006; received in revised form 3 July 2006; accepted 7 July 2006
In this research, we
synthesized nanocrystalline titanium dioxide (TiO2) powder by
hydrolyzing titanium tetraisopropoxide in a mixture of isopropanol and
deionized water. The synthesized powder
was analyzed for its phases, using XRD. Its powder morphology was determined
using TEM. TiO2 powder was in anatase phase and its particle-size
was around 5~10 nm. Uniaxially compacted structures of the synthesized powder
and commercial TiO2, were sintered in the temperature range of
1100-1600oC, to compare their densification behavior. Vickers
hardness and compression tests were performed to evaluate their mechanical
properties. Maximum compressive strength of 364.1±10.7 MPa was achieved in
structures sintered at 1500oC. © 2006 Elsevier B.V. All rights
reserved.
Keywords: Titanium
dioxide; Sol–gel; Nanopowder; Synthesis; Mechanical properties
4.
Kalita, S.J., Bhardwaj, A., and Bhatt, H., 2006.
Nanocrystalline calcium phosphate ceramics in biomedical engineering. Materials
Science and Engineering C 27 (2007) 441–449; doi:10.1016/j.msec.2006.05.018. (Article in press, available online at
www.sciencedirect.com)
Nanocrystalline
calcium phosphate based bioceramics are the new rage in biomaterials research.
Conventionally, calcium phosphates based materials are preferred as bone grafts
in hard tissue engineering because of their superior biocompatibility and
bioactivity. However, this group of bioceramics exhibits poor mechanical
performance, which restricts their uses in load bearing applications. The
recent trend in bioceramic research is mainly concentrated on bioactive and
bioresorbable ceramics i.e. hydroxyapatite, bioactive glasses, tricalcium
phosphates and biphasic calcium phosphates as they exhibit superior biological
properties over other materials. In recent times, the arena of nanotechnology
has been extensively studied by various researchers to overcome the existing
limitations of calcium phosphates, mainly hydroxyapatite, as well as to
fabricate nanostructured scaffolds to mimic structural and dimensional details
of natural bone. The bone mineral
consists of tiny HAp crystals in the nano-regime. It is found that
nanocrystalline HAp powders improve sinterability and densification due to
greater surface area, which could improve the fracture toughness and other
mechanical properties. Nano HAp is also expected to have
better bioactivity than coarser crystals. Nanocrystalline calcium phosphate has the
potential to revolutionize the field of hard tissue engineering from bone
repair and augmentation to controlled drug delivery devices. This paper reviews the current state of
knowledge and recent developments of various nanocrystalline calcium phosphate
based bioceramics from synthesis to characterization. ©
2006 Elsevier B.V. All rights reserved. Keywords: Bioceramics; Nanophase
materials; Calcium phosphates; Biomaterials
5.
Kalita, S.J. and
Three dimensionally interconnected porous resorbable
beta-tricalcium phosphate (b-TCP)
ceramic scaffolds were developed using the indirect fused deposition modeling process.
b-TCP was doped with Mg and Zn, separately, to improve
its sintering kinetics and facilitate fabrication of viable porous scaffolds.
Effects of Mg and Zn on sintering kinetics and densification of b-TCP were studied. Fabricated porous scaffolds were
tested for their failure strength under uniaxial compressive loading. Results showed that the scaffolds of Mg doped b-TCP possessed higher compression strength than the structures
of Zn doped _-TCP. X-ray powder diffraction technique was used to analyze the
phase purity and phase transformation. Key words: Porous Scaffolds,
Tricalcium Phosphate, Fused Deposition Modeling, Rapid Prototyping. © 2005
Science Publications.
6.
Bhatt, H., and Kalita, S.J., 2007. Influence of Oxide-based Sintering Additives on
Densification and Mechanical Behavior of Tricalcium Phosphate (TCP). Journal of Materials Science: Materials in
Medicine, DOI: 10.1007/s10856-006-0091-0
(Published online: 9 Jan 2007)
In this research, we
studied and analyzed the effects of four different oxide-based sintering
additives on densification, mechanical behavior, biodegradation and
biocompatibility of tricalcium phosphate (TCP) bioceramics. Selective sintering
additives were introduced into pure TCP ceramics, in small quantities, through homogeneous
mixing, using a mortar and pestle. The
consequent powders of different compositions were pressed into cylindrical
compacts, uniaxially and sintered at elevated temperatures, 1150oC
and 1250oC, separately in a muffle furnace. X-ray powder diffraction technique was used
to analyze the phase-purity of TCP after sintering. Hardness of these sintered
specimens was evaluated using a Vickers hardness tester. Sintered cylindrical
samples were tested under uniaxial compressive loading, as a function of composition
to determine their failure strength. Biodegradation studies conducted using
simulated body fluid under dynamic environment, revealed that these additives
could control the rate of resorption and hardness degradation of TCP ceramics. Received:
15 April 2005 / Accepted: 22 February 2006
© Springer Science+Business Media, LLC 2007
7.
Kalita, S.J. and Bhatt, H., 2006. Nanocrystalline
Hydroxyapatite doped with Magnesium and Zinc: Synthesis and Characterization. Materials
Science and Engineering C (2006), doi:10.1016/j.msec.2006.09.036. (Article in press, available online at www.sciencedirect.com), Received 18 February 2006; received in revised form
19 September 2006; accepted 23 September 2006.
During
recent years, there have been efforts in developing nanocrystalline
bioceramics, to enhance their mechanical and biological properties for use in
tissue engineering applications. In this
research, we made an attempt to synthesize nanocrystalline bioactive
hydroxyapatite (Ca10(PO4)6(OH)2,
HAp) ceramic powder in the lower-end of nano-range (2-10 nm), using a simple
low-temperature sol-gel technique and studied its densification behavior. We further studied the effects of metal ion
dopants during synthesis on powder morphology, and the properties of the
sintered structures. Calcium nitrate and
triethyl phosphite were used as precursors for calcium and phosphorous,
respectively, for sol-gel synthesis.
Calculated quantities of magnesium oxide and zinc oxide were
incorporated as dopants into amorphous dried powder, prior to calcination at
250-550oC. The synthesized
powders were analyzed for their phases using X-ray diffraction technique and
characterized for powder morphology and particle size using transmission
electron microscopy (TEM). TEM analysis
showed that the average particle size of the synthesized powders were in the
range of 2-10 nm. The synthesized
nano-powders were uniaxially compacted and then sintered at 1250oC
and 1300oC for 6 h, separately, in air. A maximum average sintered density of 3.29
g/cm3 was achieved in structures sintered at 1300oC, developed
from nano-powder doped with magnesium.
Vickers hardness testing was performed to determine the hardness of the
sintered structures. Uniaxial
compression tests were performed to evaluate the mechanical properties. Bioactivity and biodegradation behavior of
the sintered structures were assessed in simulated body fluid (SBF) and
maintained in a dynamic state. © 2006 Elsevier B.V. All rights reserved.
Keywords: Nanostructured bioceramics; Nanocrystalline
hydroxyapatite; Nano-powder; Sol–Gel; Calcium phosphate; Biomaterial
8.
Kalita, S.J., Fleming, R., Bhatt, H, Schanen, B., and Chakrabarti,
R., 2006. Development of Controlled Strength-Loss Resorbable Beta-Tricalcium
Phosphate Bioceramic Structures, Materials
Science and Engineering C (Accepted for publication).
Controlling the
strength-loss rate during biodegradation is a bottleneck in developing viable
resorbable ceramic implants. Resorbable beta-tricalcium phosphate (b-TCP) bioceramic is known for its excellent
biocompatibility. However, it exhibits
poor sinterability and poor flexural strength.
Here, we improved sintering behavior and biaxial flexural strength of b-TCP bioceramic without altering its biocompatibility
by introducing multi-oxide sintering additives, in small quantities. These additives could also tailor the rate of
resorption and hardness deterioration of b-TCP. A range
of additives were prepared and introduced into b-TCP powder.
Resultant powders were uniaxially pressed and sintered at 1250oC,
in air. Considerable improvement in
densification (up to 33%) and biaxial flexural strength (up to 43%) were
achieved. X-ray powder diffraction (XRD)
analysis confirmed that the additives didn’t alter the phase purity. In
vitro cytotoxicity and biocompatibility analyses were performed using a
prostate cancer cell-line. Results
showed that the doped and pure b-TCP structures were non-toxic and biocompatible.
9. S. J. Kalita, D. Rokusek, S. Bose,
H. L. Hosick, A. Bandyopadhyay. Effects
of MgO-CaO-P2O5-Na2O-based additives on
mechanical and biological properties of hydroxyapatite. Journal of Biomedical Materials Research
Part A, Vol. 71A,
Issue I, 2004:35-44.
In this research, we improved densification, hardness and compression
strength of synthetic hydroxyapatite (HAp) ceramics by introducing small
quantities of MgO-CaO-P2O5-Na2O-based
sintering additives. Biological
properties of HAp were not altered by this procedure. Phase analyses were done using a Philips Xpert
fully automated diffractometer with Co K-alpha radiation to understand the
influence of additives on phase purity in the final products. All compositions were characterized at green
and sintered densities, to understand the influence of additives on
densification. Some of the compositions
showed more than a 40% increase in Vickers microhardness compared to pure HAp
processed under the same conditions.
Improvement in compression strength was also detected in some
compositions. In vitro biological
testing utilized a modified human osteoblast cell line to test
biocompatibility, cell-attachment and cell proliferation. All these compositions were found non-toxic
and biocompatible. Our results indicate
that MgO-CaO-P2O5-Na2O based sintering
additives can be used to improve both mechanical and biological properties of
HAp ceramics. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 35–44,
2004. Key words: calcium phosphate; hydroxyapatite; sintering additives;
bioactive ceramics; bone cells.
10. S. J. Kalita, S. Bose, H. L. Hosick,
and A. Bandyopadhyay. CaO-P2O5-Na2O-based
sintering additives for hydroxyapatite (HAp) ceramics. Biomaterials, 25; 2004:2331-2339.
We have assessed the effect of CaO–P2O5–Na2O-based
sintering additives on mechanical and biological properties of hydroxyapatite
(HAp) ceramics. Five different compositions of sintering additives were
selected and prepared by mixing of CaO, P2O5, and Na2CO3
powders. 2.5wt% of each additive was combined with commercial HAp powder,
separately, followed by ball milling, and sintering at 1250oC and
1300oC in a muffle furnace. Green and sintered densities of the
compacts were analyzed for the influence of additives on densification of HAp.
Phase analyses were carried out using an X-ray diffractometer. Vickers
microhardness testing was used to evaluate hardness of sintered compacts of
different compositions. A maximum microhardness of 4.6 (70.28) GPa was attained
for a composition with2.5 wt% addition of CaO:P2O5:Na2O
in the ratio of 3:3:4. Results from mechanical property evaluation showed that
some of these sintering additives improved failure strength of HAp under
compressive loading. Maximum compressive strength was observed for samples
with2.5 wt% addition of CaO. Average failure strength for this set of samples
was calculated to be 220 (750) MPa. Cytotoxicity, and cell attachment studies
were carried out using a modified human osteoblast cell line called OPC-1. In
vitro results showed that these compositions were non-toxic. Some sintering aids
enhanced cell attachment and proliferation, which was revealed from SEM
examination of the scaffolds seeded with OPC-1 cells. © 2003 Elsevier Ltd. All
rights reserved. Keywords: Hydroxyapatite; Calcium phoshpate;
Sintering additives; Bioactive ceramics; Bone cells
11. S. J. Kalita, S. Bose, H. L. Hosick,
and A. Bandyopadhyay. Development of controlled porosity polymer-ceramic
composite scaffolds via fused deposition modeling. Materials Science and Engineering: C, 23;
2003:611– 620.
This research is focused on development and fabrication of controlled
porosity polymer-ceramic composite scaffolds, with 3-D interconnectivity
designed to promote richer supply of blood, oxygen and nutrients for healthy
in-growth of bone cells. Particulate-reinforced polymer-ceramic composites were
developed by high shear mixing of polypropylene (PP) polymer and tricalcium
phosphate (TCP) ceramic. Processing aids were used to improve plasticity and
processibility to the composites. Controlled porosity scaffolds were fabricated
via the fused deposition process, one of the commercially available rapid
prototyping (RP) techniques. These porous scaffolds were characterized for
their use as bone grafts in terms of physical, mechanical and biological
properties. Hg-porosimetry was performed to determine pore size and their
distribution. Scaffolds with different complex internal architectures were also
fabricated using this composite material. Tensile properties of neat PP (as
received), PP with processing aids (without TCP) and PP-TCP composite (with
processing aids) were evaluated and compared using standard dog bone samples.
Uniaxial compression tests were performed on cylindrical porous samples with an
average pore size of 160 Am and varying vol.% porosity (36%, 48% and 52%). Samples
with 36 vol.% porosity showed the best compressive strength of 12.7 MPa.
Cytotoxicity and cell proliferation studies were conducted with a modified
human osteoblast cell-line (HOB). Results showed that these samples were
non-toxic with excellent cell growth during the first two weeks of in vitro
testing. © 2003 Elsevier B.V. All rights reserved. Keywords:
Rapid prototyping; Bio-composites; Fused deposition modeling; Bone graft;
Porous materials
12. S.
J. Kalita, S. Bose, H. L.
Hosick, and A. Bandyopadhyay. Porous calcium aluminate ceramics for
bone-graft applications. Journal of
Materials Research, Vol.17 No. 12; 2002:3042-3049.
Calcium aluminate scaffolds with controlled porosity were processed for
bone-graft applications. Indirect fused deposition process was used to
fabricate these structures. Phase analyses were done using x-ray diffraction
technique on powdered samples of calcium aluminates at different compositions.
Hg porosimetry was used to determine the pore sizes and the pore volumes
present in these controlled porosity structures at different calcium aluminate
compositions. Cylindrical samples were tested under uniaxial compressive
loading as a function of composition and volume fraction porosity (VFP).
Samples of 29% and 44% VFP (designed) with average pore size of 300 mm showed compressive strength between 2 and 24
MPa. Cytotoxicity and cell proliferation studies were conducted with a modified
human osteoblast cell line (HOB). These materials showed good cell attachment
and a steady cell growth behavior with HOB cells during the first three weeks
of in vitro analyses. © 2002 Materials Research Society
Abstracts
of Peer Reviewed International Conference Proceeding Papers
13. Hong, S.J., Bhatt, H., Suryanarayana, C., and
Kalita, S.J., 2005. Synthesis
of nano-size hydroxyapatite (HAp) powders by mechanical alloying. Advances in Bioceramics and Biocomposites, D.
Zhu and W. M. Kriven, Editors; CESP,
Vol. 26, Issue 6, p33-39.
Nano hydroxyapatite (Ca10(PO4)6(OH)2,
HAp) powders were synthesized by solid-state reaction of Ca(OH)2 and
P2O5 mixtures in a high-energy SPEX 8000 shaker mill,
using hardened steel vial and balls. The phase analysis was carried out using
X-ray powder diffraction technique. Transformation of Ca(OH)2 and P2O5
mixture to HAp phase was first observed after 1 h of milling. The powder
milled for 3 h showed prominently the presence of HAp phase. TEM analysis
revealed that as-synthesized HAp powder was in the range of 20-60 nm. Measured
quantities of synthesized nano-powders were pressed uniaxially in a steel mold
to prepare dense ceramic structures for densification studies. These green
structures were subjected to sintering studies at 1300 oC for 6 h
when the highest sintered density of 3.17 g/cc was achieved. © 2005 American Ceramic Society
14. Bhatt, H., and Kalita, S.J., 2005. Synthesis and
sintering studies of nanocrystalline hydroxyapatite powders doped with
magnesium and zinc. Advances in Bioceramics and Biocomposites, D. Zhu and W. M. Kriven,
Editors; CESP, Vol. 26, Issue
6, p17-23.
In this research, we have synthesized nanocrystalline
hydroxyapatite (Ca10(PO4)6(OH)2,
HAp) powders doped with magnesium and zinc using the water-based sol-gel
technique and characterized them. Calcium nitrate and triethyl phosphite were
used as starting materials. These chemicals were dissolved in distilled water,
separately, under vigorous stirring. As-prepared calcium nitrate sol was added
drop wise into the hydrolyzed phosphite sol and then aged and dried. Dried gel
was then crushed into fine white powders with the help of mortar and pestle and
a measured amount of magnesium oxide and zinc oxide powders were added to the
crushed amorphous powders, separately. Calcination was carried out at 250-500oC.
Morphology of the powders was determined using transmission electron
microscopy. TEM results revealed that the particle size diameter of powders
were in the range of 5-10 nm. Phase analyses were carried out using powder
X-ray diffraction technique. As-synthesized powders were also pressed
uniaxially in a steel mold to prepare dense ceramic structures. These green
structures were sintered at 1300oC for 6 h in a muffle furnace for
densification. Highest sintered density of 3.29 g/cc was measured for
magnesium-doped powder. © 2005 American
Ceramic Society
15. S. J. Kalita, S. Bose, H. L. Hosick
and A Bandyopadhyay. Oxide Based
Sintering Additives for HAp Ceramics. Ceramic Transactions, Vol. 147, edited by Veeraraghavan (V) Sundar,
Richard P. Rusin, and Claire A. Rutiser (2003).
With the increase in
average age of the human population, the challenge of treating bone defects and
repairs is rising and overall orthopedic market is growing. Hydroxyapatite
(HAp), a bioactive ceramic, is known for its excellent biocompatibility, but
shows poor mechanical performance.
In our research, we have tried to improve mechanical performance of
commercial HAp by introducing small quantities of various sintering
additives. A range of oxide based sintering
additives were selected and prepared based on already reported results of their
biocompatibility when tested individually or in addition with other
materials. Dense compacts were prepared
using a uniaxial press mold with an average green density of 1.6 g/cc. Results showed that some of these sintering additives
significantly improved densification and hardness of synthetic HAp. A maximum bulk density of 3.05 g/cc was
reported. Vickers micro hardness testing
showed that there is 50% increase in the hardness of HAp with some of the
sintering aids. Cytotoxicity and cell
proliferation studies were conducted using a modified human osteoblast
cell-line (HOB). In vitro testing with osteoprecursor cells (OPC1) showed that most
of these compositions were non-toxic.
Microscopic observation revealed that OPC1 cells were anchored and
attached on matrices of most of these compositions. This paper will present physical, mechanical
and cytotoxicity test results of different compositions of hydroxyapatite (HAp)
with various sintering additives. © 2003 American Ceramic Society
16. S. J. Kalita, J. Finley, S. Bose, H. L. Hosick and A.
Bandyopadhyay. Development of Porous
Polymer-Ceramic Composites as Bone Grafts. Mat. Res. Soc. Symp. Proc.
Vol. 726, Q5.8, 2002.
Biomaterials have
made significant contributions to the advancement of modern health care and
drug delivery industries. The present research is based on development of
porous polymerceramic composite scaffolds using polypropylene (PP) polymer and
tricalcium phosphate (TCP) ceramic for bone-graft applications. Three
dimensionally interconnected controlled porosity scaffolds were fabricated
using a fused deposition modeling (FDM) system. First, ceramic and polymeric
materials were compounded under high shear using a torque rheometer. Compounded
materials were then extruded to a 1.78mm diameter continuous filament using a
single screw extruder. These filaments were used as a feedstock material for an
FDM 1650 machine for direct fabrication of controlled porosity parts.
Hg-porosimetry was done to determine pore size and their distribution in these
structures. Tensile properties of neat composites and as received polymer were
measured and compared using standard dog bone samples. Uniaxial compression
tests were performed on cylindrical porous samples having average pore size of
160 µm and 36 vol% porosity. These samples showed an average ultimate
compressive strength of 12.7 MPa.
Average compressive modulus was calculated as 263 MPa. Cytotoxicity and
cell proliferation studies were conducted with OPC1 modified human osteoblast
cell-line. It was found that composite matrices were non-toxic and they showed
excellent cell growth with OPC1 cells. Mat. Res. Soc. Symp. Proc. Vol. 726 © 2002
Materials Research Society
17. S. J.
Kalita, S. Bose, H. L. Hosick, S. A. Martinez and A. Bandyopadhyay.
Calcium Carbonate Reinforced Natural polymer Composite for Bone Grafts. Mat. Res. Soc. Symp. Proc. Vol. 724,
N8.18, 2002.
Biomaterials have made significant contributions to
the advancement of modern health care and drug delivery industries. The
present research is based on development of porous polymer-ceramic composite
scaffolds using polypropylene (PP) polymer and tricalcium phosphate (TCP)
ceramic for bone-graft applications.
Three dimensionally interconnected controlled porosity scaffolds were
fabricated using a fused deposition modeling (FDM) system. First, ceramic and polymeric materials were
compounded under high shear using a torque rheometer. Compounded materials were then extruded to a
1.78mm diameter continuous filament using a single screw extruder. These filaments were used as a feedstock
material for an FDM 1650 machine for direct fabrication of controlled porosity
parts. Hg-porosimetry was done to determine pore size and their distribution in
these structures. Tensile properties of neat composites and as received polymer
were measured and compared using standard dog bone samples. Uniaxial compression tests were performed on
cylindrical porous samples having average pore size of 160 µm and 36 vol%
porosity. These samples showed an average ultimate compressive strength of 12.7
MPa. Average compressive modulus was calculated as 263 MPa. Cytotoxicity and cell proliferation studies
were conducted with OPC1 modified human osteoblast cell-line. It was found that composite matrices were
non-toxic and they showed excellent cell growth with OPC1 cells. Mat.
Res. Soc. Symp. Proc. Vol. 724 © 2002 Materials Research Society
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