bluuebunny/crossref_metadata_2025 huggingface dataset:
Possible Approaches in Modelling Rearrangement in a Microstructured Material
Authors: Federico Salvatore , Grillo Alfio , Herzog Walter , Giaquinta Gaetano , Imatani Shōji
Published: March 2009

Biological materials can be regarded as composites with spheroidal and fibre-like
inclusions, representing cells and collagen fibres, respectively. The orientation and arrangement of
the inclusions in a biological tissue is crucial to the determination of the mechanical properties of
the material. Furthermore, the reorientation and rearrangement of the inclusions due to the
deformation and external forces is of primary interest when dealing with growth and remodelling.
We propose to look at the presence of inclusions as a source of internal hyperstaticity: when the
material undergoes deformation, a generic inclusion is drifted by the deformation, but at the same
time it “feels” the stress field and tends to carry a portion of stress proportional to its stiffness
relative to that of the surrounding matrix. With this assumption, we can extend the classical “drift”
evolution law for the unit vector field, in order to take the hyperstaticity into account. This method
might be used in the description of remodelling in disordered media, such as biological tissues, and
may be extended to investigate the reorientation of preferred directions of micro-structural elements
in media described with a continuum approach.
Analysis of Cavity Tool Stresses in Channel Angular Extrusion
Authors: Lupoi R. , Osman (1) F.H.
Published: March 2009

The Channel Angular Extrusion (CAE) technique is a process, in which a deformable
solid material is led to yielding through the intersection of inclined channels. Compared to classic
plastic deformation, the process is technically simple but the material experiences, instantly, large
plastic deformation. The deformation occurs locally and high internal stresses develop during the
process. In most cases the process is used for grain size refinement. Equal Channel Angular
Extrusion (ECAE) is a special case where the intersecting channels are of equal cross sections.
In this paper, an analytical study of the internal stresses and those developed along CAE tools is
presented. A deformation model is introduced for the general process of channel extrusion in
which the intersecting channels are not necessarily equal. The procedure splits the material at the
intersection of the channels into two zones; one causes the deformation while the other remains
rigid. The analysis is also applied to the particular case of ECAE, and the results are compared
with those obtained from a finite element analysis and the overall experimental pressure.
Failure Mode Analysis for Column over Designed Ductile Frames
Authors: Zhao Yan Gang , Geng Yue Feng , Yoshihara Kazuhiro
Published: March 2009

In ultimate asseismic design of ductile frame structures, plastic deformation and plastic
hinge are generally permitted, and some preferred failure modes are often selected. It is an
important problem that whether the designed structure collapses according to the designed failure
mode, because of the large uncertainties included in external loads and member strength. In this
paper, an identification procedure of failure modes for frame structures is developed, and the likely
collapse modes of frame structures under uncertain load and member strength are investigated
under assumption of normal distributed and non-normal distributed external loads and member
strength. It is found that the occurrence order of likely collapse mode is much influenced by the
distribution of the random variables. The occurrence order of collapse modes for column over
designed structures are investigated and it is found that the increase of column over-design factor
can effectively avoid the story collapse mode in probabilistic means.
Superplastic Properties and Microstructure of Friction Stir Welded Joints of Zn-22wt.%Al Alloy
Authors: Tanaka Tsutomu , Hirata Tomotake , Wook Chung Sung , Takigawa Yorinobu , Higashi Kenji
Published: March 2009

Deformation mechanism of room-temperature superplasticity in Zn-22wt%Al alloy was
investigated by the direct observation during deformation. It was revealed that the dominant
deformation mechanism of room-temperature superplasticity was grain boundary sliding. Also,
superplastic properties and microstructure of friction stir welded Zn-22wt.%Al alloy were
investigated, where Friction Stir Welding (FSW) has received a great deal of attention as a new
solid-state welding technique. A sound jointing material was obtained successfully, and extremely
fine and equiaxed grains were created in the stir zone. In addition, it was indicated that
superplastic forming of the FSWed Zn-22wt.%Al alloy could be feasible. However, the tensile
strength and elongation of the joint at room temperature were lower than that of the base material.
Residual Stresses in TIG-Welded I-Beams. Experimental Test-Setup and Validation of Numerical Model
Authors: De Strycker Maarten , Buffel Peter , Belis Jan , Fimmers Christof , Vanlaere Wesley , Lagae Guy
Published: March 2009

The presence of residual stresses is a determining factor in the buckling behaviour of
steel beams. It is therefore necessary to know the magnitude and the distribution of residual stresses
in welded beams. Experimental measurements of these residual stresses are expensive, timeconsuming
and they give no insight in the evolution of the stresses during the welding process. For
these reasons it is interesting to have a numerical model which allows a prediction of the residual
stresses due to welding and which allows a study of the parameters that have an influence on the
residual stresses (e.g. yield stress, heat-input, thermal expansion coefficient, …).
Such a numerical model can result in a proposal for a welding process that leads to less detrimental
residual stress distributions in welded I-beams.
However, the results of the numerical model must always be checked with reality. This contribution
contains the experimental verification of the finite element model for both single plates and I-beams
with rather small dimensions.
First, an overview of generally accepted influencing factors on the residual stresses is given. After
this introduction, a setup which allows control of the parameters for making reproducible weld
seams is presented. This setup is usable for both plates and I-beams. Next it is described how the
residual stresses in a plate and a beam were measured. Finally the results obtained from different
configurations in the experiments are compared with the results from the FE-model. It is shown that
the FE-model gives reliable predictions for the residual stresses.
Effects of Loading Speed and Shear Prestrain on Adhesive Fatigue Strength in Single-Lap Joint
Authors: Takiguchi Michihiro , Yoshida Fusahito
Published: March 2009

The adhesive fatigue strength was investigated by performing repeated tensile lap shear
experiments of an aluminum single-lap joint bonded with highly ductile acrylic adhesive. In
load-controlled fatigue tests, progressive transverse shear deformation of the adhesive layer took
place, and it led to the final fracture of the joint. The fatigue strength becomes higher with increasing
loading speed, especially at low-cycle fatigue region. From experiments on shear-prestrained
specimens, it was found that the prestrain does not affect so much the fatigue life. In order to discuss
the behavior of progressive shear strain accumulation (viscoplastic ratcheting) of adhesive under
cyclic loading, the numerical simulation of ratcheting was conducted using a constitutive model of
elasto-viscoplasticity for the adhesive.
A Modified Kinematic-Hardening Viscoplasticity Model for Off-Axis Creep Behavior of Unidirectional CFRPs at High Temperature
Authors: Kawai Masamichi , Zhang Jian Qi
Published: March 2009

A macromechanics constitutive model to describe the anisotropic creep behavior of
unidirectional composites under off-axis loading conditions is developed with a particular emphasis
on accurate prediction of temporal creep softening due to stress variation. A viscoplasticity model
that takes account of a combined isotropic and kinematic hardening is adopted as a base for this
formulation, and the evolution equation of the kinematic hardening variable is elaborated to
enhance the accuracy of prediction of the transient creep softening due to stress variation. Validity
of the modified kinematic-hardening viscoplasticity model is evaluated by comparing with the
experimental results on unidirectional T800H/3631 carbon/epoxy composites. It is demonstrated
that the proposed model can adequately describe the off-axis creep behavior of the unidirectional
CFRP laminate under constant and variable stress conditions.
Inspection and Model Experiment of a Damaged Arch Bridge
Authors: Fan Ying Fang , Hu Zhi Qiang , Zhou Jing
Published: March 2009

The structural behavior of an old six-span reinforced concrete arch bridge, which has
been in service for about 40 years, is investigated. Field monitoring (inclusive of test of material
property, static and dynamic test of the bridge) was conducted, static and dynamic responses of
the bridge are obtained. Based on the primitive bridge, a scaled one-span bridge model was
fabricated by organic-glasses. Both the static and dynamic tests were executed on the bridge
model in the laboratory. Since the arch rib is the crucial member for the arch bridge, 7 notches
were cut on both arch ribs of the bridge model to simulate different damages of the arch rib.
Mechanical responses of the bridge with different damages on the arch ribs were achieved. FEM
analyses were preformed on the bridge as well. Numerical results show good agreement with the
experimental results.
Deformation and Failure Behaviors of PC/ABS (50/50) Blends under Impact
Authors: Machmud M. Nizar , Omiya Masaki , Inoue Hirotsugu , Kishimoto Kikuo
Published: March 2009

An instrumented-drop weight impact test carried out at room temperature under a range
of loading rates was applied to study the deformation and failure behaviors of PC/ABS (50/50)
blends. Actually, these blends have different type of ABS, one grade of the blends is the blend
containing small-sized particles of rubber and another grade is the blend containing larger-sized
particles of rubber in the ABS systems. Testing results showed that both of the blends generally
exhibited similar behaviors but they were totally different under 3 m/sec. A weld line-like formation
captured on the fracture surface was found in each of the blends. Preliminary study using scanning
electron microscope (SEM) indicated that crack also propagated along the weld line. Fracture of the
blends might be initially induced due to fracture of the weld lines. Hence, it has been suspected as a
factor affecting behavior of the blends. Since existence of the weld line-like formation has not been
found in fractured ABS materials, it is necessary to point out the complex relationship among of the
ABS composition, the existence of the weld line and the weld line quality in the blends. A finite
element (FE) simulation of the testing was carried in order to determine whether the weld line
strength is significant enough affects the behaviors. Although the model was generated using
estimated failure criterion for the weld line, the simulation results showed that weld line strength
might influence the blends behavior.
Nanoindentation-Induced Collective Dislocation Behavior and Nanoplasticity
Authors: Shibutani Yoji , Tsuru Tomohito
Published: March 2009

The present paper summarizes the crystallographic dependence of the displacement burst
behavior observed in nanoindentation using two single crystalline aluminum (Al) materials and
copper (Cu) with three kinds of surface indices, namely (001), (110) and (111). From the critical
indent load at the first burst, the critical resolved shear stresses (CRSSs) of the collective dislocation
nucleation were estimated in reference to molecular dynamics (MD) simulations. These are almost
one-tenth of the shear modulus, which are close to the ideal values. We explain the nanoplastic
mechanics by a comprehensive energy balance model to describe the linear relation between the
indent load and the burst width of the first displacement burst and by the nucleation model consisting
of three-dimensional discrete dislocations to evaluate the number of dislocations nucleating. The
distance between the emitted dislocation loops of Al is found to be fairly large. Thus, Al is expected
to exhibit a less tangled network of dislocations just below the indentation than Cu, which has a lower
stacking fault energy.
Constitutive Relation of Open-Celled Metal Foams Based on the Mesoscopic Behavior of Random Cells
Authors: Hu Ling Ling , Huang Xiao Qing , Tang Li Qun
Published: March 2009

The constitutive relation for open-celled metal foams with random characteristics of cells
was constructed based on the mechanical behavior and the distribution of the cells, which implied
the effect of the mesoscopic characteristics of the cells on the macroscopic behavior of the foam.
The constitutive relation was able to represent the whole three phases of the stress-strain curve of
the open-celled metal foam with merely one expression. Besides, the explicit expressions for the
foam’s yield strain and yield stress were supplied. Experimental data was employed to check the
constitutive relation. It was found that the constitutive relation was able to represent accurately the
whole compression process of the foams, and the calculated yield points had a good agreement with
the experimental results.
Combined Adaptive Finite Element Method and J-Domain Integral Technique for Crack Problems
Authors: Potjananapasiri Kobsak , Phongthanapanich Sutthisak , Bhandhubanyong Paritud , Dechaumphai Pramote
Published: March 2009

An adaptive finite element method for analyzing two-dimensional and axisymmetric
nonlinear elastic fracture mechanics problems with cracks is presented. The J-integral is used as a
parameter to characterize the severity of stresses and deformation near a crack tip. The domain
integral technique is utilized as the J-integral solution scheme with the 9-node degenerated crack tip
elements. The solution accuracy is further improved by incorporating an error estimation procedure
to a remeshing algorithm with a solution mapping scheme to resume the analysis at a particular load
level after the adaptive remeshing technique has been applied. Two benchmark problems are
analyzed to evaluate the efficiency of the combined procedure.
Mechanics Analysis on Bar Cutting Based on High Speed and Restrained State
Authors: Qi Hui Ping , Li Yong Tang , Song Jian Li , Fu Jian Hua , Ting Kwun Lon
Published: March 2009

There are many problems in the common baiting methods, such as bad cross-section
quality, low efficiency and so on. In order to overcome these disadvantages, a new bar cutting
technology based on high speed and restrained state is put forward in the paper. The cutting process
and cutting mechanics were analyzed. The stressing intensity factor and fracture toughness were
introduced to analyze the influence of loading velocity on the cutting surface quality. By means of
the dislocation theory, the influence of loading velocity on the fracture process was researched.
Numerical simulation and experiments were carried out, and the results were conformed well with
the theoretical ones.
Effects of Roller Working and Ion Nitriding on Fatigue Properties of Eutectoid Steel
Authors: Zhang Mian , Nishida Shinichi , Hattori Nobusuke , Sun Wen Xian
Published: March 2009

In this study, the authors have investigated and compared the effects of roller working
and ion nitriding on fatigue properties of eutectoid steel. Five kinds of roller worked and two kinds
of ion nitrided specimens were used in this test. The fatigue test was performed using a rotating
bending fatigue testing machine to evaluate the fatigue strength of roller worked and ion nitrided
eutectoid steel. The fatigue test result shows that roller working is more effective on improving the
fatigue strength of the material than ion nitriding. On the other hand, the ion nitriding can much
greatly increase the surface hardness than the roller working. In the case of roller working, the
fatigue properties are improved by the three main factors which are compressive residual stress,
work hardening and fiberized micro-structure.
Effect of Additional Shear Strain Layer on Microstructure and Tensile Strength of Fine Wire
Authors: Kajino Satoshi , Asakawa Motoo
Published: March 2009

The mechanical and electrical applications of fine wires (D = 0.1 mm) has become more widely
spread. In general, it is well known that fine drawn wires have high tensile strength while
maintaining ductility. It has been determined that a hardened layer of around 0.04 mm in depth,
referred to as the “additional shear strain layer,” is generated beneath the surface layer of the wire,
and this additional shear strain layer affected the tensile strength of the fine wire. As an origin of
this phenomenon, it was ascertained that the microstructure of surface layer was finer than that of
center layer. The purpose of this paper is to investigate the effect of die angle on the microstructure
and the tensile strength of the additional shear strain layer. The tensile test was performed as the
surface layer was thinned by electro-polishing, and the crystal orientation and the crystal grain were
measured via EBSD. As a result, it was ascertained that die angle affected the tensile strength and
crystal grain refinement of the additional shear stray layer.
Forming Load Characteristics of Forward and Backward Tube Extrusion Process in Combined Operation
Authors: Seo Jung Min , Jang Dong Hwan , Min K.H. , Koo H.S. , Kim S.H. , Hwang Beong Bok
Published: March 2009

Combined extrusion processes generally have advantages of forming in terms of the
minimum deformation power since the material is pressed through two or more orifices
simultaneously. This paper is concerned with the analysis of forming load characteristics of a
forward-backward can extrusion process using thick-walled pipe as an initial billet. The combined
tube extrusion process was analyzed by using a commercial finite element code. A thick-walled pipe
was selected as an initial billet and the punch geometry has been chosen on the basis of ICFG
recommendation. Several tool and process parameters were employed in this analysis and they are
punch nose radius, backward tube thickness, punch face angle, and frictional conditions, respectively.
The main purpose of this study is to investigate the effect of process parameters on the force
requirements in combined extrusion process. The possible extrusion process to form a
forward-backward tube parts in different process sequences were also simulated to investigate the
force requirements in sequential operations, i.e. separate operations. It was easily concluded from the
simulation results that lower forming load was predicted for the combined extrusion, compared to
those for separate sequential operations. It was also revealed that the punch nose radius and the punch
face angle have little effect on the force requirements and the forming load increases significantly as
the frictional condition along tool-workpiece interface becomes severe. The simulation results in this
study suggest that the combined extrusion process has strong advantage in terms of force
requirements as long as the simultaneous material flow into multiple orifices could be closely
controlled.
Quantitative Description of Microscopic Plastic Deformation of Polycrystalline Aluminum Using Laser-Scanning Microscope
Authors: Song Hua Lin , Abe Takeji
Published: March 2009

The mi c ros copi c pl as t i c de format ion behavior of
pol yc r ys t al l ine aluminum shee t dur ing uni axi al t ens ion i s exper iment al l y
inves t iga t ed b y a confoc al l a s e r - s canning mi c ros cope. The gr ain rot at ion i s
me asur ed f rom images of spec imen sur fa c e be fore and a f t e r deformat ion i s
propos ed. Digi t al image proc es s ing t e chnique i s appl i ed to the sur f a c e
gr ain image t aken by the CCD c ame ra . The exper iment al dat a obt ained f rom
man y gr a ins a re s t a t i c al l y proce s s ed. I t i s shown that the gr ain rot at ion i s
l a rge when the shape of gr ain i s clos e to a ci r cl e. Di s cus s ions a r e made on
the r el at ion be twe en gra in rot at ion, s t ra ins of gr ains and va r ious f a ctor s
af f e ct ing them, such as gr ain s i z e, gra in shape and s l ip- l ine angl e.
Simulation of Inelastic Deformation and Thermal Mechanical Stresses in Twin-Roll Casting Process of Mg Alloy
Authors: Hu Xiao Dong , Ju Dong Ying
Published: March 2009

Twin-roll thin strip casting process combines casting and hot rolling process into a single
step; in which melt and solid states exist in the casting region, so its deformation is more complex
than rolling process. In this paper, Anand’s model, a unified visco-plasticity constitutive model, was
employed to simulate the highly nonlinear behavior in the twin-roll casting process. Anand model’s
parameters were regressed based on compression tests at various temperature and strain rate for
magnesium alloy AZ31. To calculate the thermal mechanical stresses, the thermal flow of twin-roll
casting process was simulated firstly; then stresses were calculate, in which the temperature field
result of thermal flow was imposed as body load, and a small displacement load along roller
tangential direction was imposed simultaneously in order to simulate rolling action. The deformation
results can well describe the forward slip zone, backward slip zone and melt eddy zone in the casting
region. Based on the results, the applicability of Anand’s model on twin-roll casting process was
discussed.
Comparison of Age-Hardening Characteristic in Thixo-Cast and Rheo-Cast T5-A356 Alloys by Nanoindenter and AFM
Authors: Cho S.H. , Youn Sung Won , Kang C.G.
Published: March 2009

The nano/microstructure and mechanical/tribological properties of the eutectic regions in
thixo/rheo-cast A356 alloy parts were investigated using nano/micro-indentation and mechanical
scratching, combined with optical microscopy and atomic force microscopy (AFM). Most eutectic
silicon crystals in the A356 alloy showed a modified morphology as fine-fibers. The aging
responses of the eutectic regions in both the thixo/rheo cast A356 alloys aged at 150 0C for different
times (0, 2, 4, 8, 10, 16, 24, 36, and 72h) were investigated. Both Vickers hardness (HV) and
indentation hardness (HIT) test results showed almost the same trend of aging curves, the peak was
obtained at the same aging time of 10 h, and in tribological properties of thixo/rheo-cast, the friction
coefficient of thixo-cast was investigated lower than that of rheo-cast.
Study on Nanolithography Process of Polycrystalline Copper Using Molecular Dynamic Simulation
Authors: Kim Chan Il , Kim Young Suk , Hyun Sang Il , Yang Seung Han , Park Jun Young , Na Kyoung Hoan
Published: March 2009

Molecular dynamics simulations are performed to verify the effect of grain boundary on
nanolithography process. The model with about two hundred thousand copper (Cu) atoms is
composed of two different crystal orientations of which contact surfaces are (101) and (001) planes.
The grain boundary is located on the center of model and has 45 degreeangle in xz-plane. The tool is
made of diamond-like-carbon with the shape of Berkovich indenter. As the tool is indented and
plowed on the surface, dislocations are generated. Moreover, during the plowing process, the steps as
well as the typical pile-ups are formed in front of the tool. These defects propagate into the surface of
the substrate. As the tool approaches to the grain boundary, the defects are seen to be accumulated
near the grain boundary. The shape of the grain boundary is also significantly deformed after the tool
passes it. We observed the forces exerted on the tool by the contact with substrate, so that the friction
coefficients can be obtained to address the effect of the grain boundary on the friction characteristics.
Characterization of PCL/HA Composite Scaffolds for Bone Tissue Engineering
Authors: Hyun Yong Taek , Kim Seung Eon , Heo S.J. , Shin Jung Woog
Published: March 2009

Porous and bioactive composite scaffolds based on poly ε-caprolactone(PCL) and
hydroxyapatite(HA) were successfully fabricated by solvent casting and salt leaching method. The
scaffolds have interconnected pore structure with pore size ranging from 10μm to 500μm. The pore
size of PCL scaffold and PCL/HA scaffold were similar to that of the salt particles. The pore walls
became thick and the small pores on the surface of macropores were formed as the HA increased.
MTT assay showed that HA content did not affect initial cell attachment in both PCL scaffolds and
PCL/HA scaffolds. The osteoblasts proliferated in both scaffolds, but the cell number was higher in
the PCL/HA composite scaffolds. It was found that the incorporation of hydroxyapatite enhances
bone cell proliferation rather than initial cell attachment in PCL/HA composite scaffolds. The
results suggest that the PCL/HA composite scaffolds have a potential for the bone tissue
engineering applications.
Effects of Vitamin K2 on Adipogenic and Osteogenic Differentiation in Mesenchymal Stem Cells from Human Umbilical Cord Blood
Authors: Yeum Chung Eun , Park Seung Yeon , Kang Tae Jin , Han Hoon , Chae Gue Tae
Published: March 2009

Mesenchymal stem cells(MSCs) have the potential to self-replicate, proliferate and
differentiate into chondrocytes, adipocytes, osteocytes and myocytes. Recent studies indicate that
vitamin K2 plays a role in bone metabolism. But the mechanism is still unclear. We evaluated effect
of vitamin K2 on osteogenesis and adipogenesis of MSCs from umbilical cord blood(UCB). By
exposing MSCs to osteogenic and adipogenic medium with and without vitamin K2, the effects of
vitamin K2 were analyzed. The results showed that vitamin K2 inhibits adipogenesis while at the
same time it stimulates osteoblastic differentiation. These data are expected to provide novel
information needed for successful therapeutic development for various types of osteoporosis and
similar diseases related to bone formation.
Zonal Poisson Effect on the Chondron Deformation in Articular Cartilage under Compression
Authors: Choi Jae Bong
Published: March 2009

The objective of this study was to quantify the zonal difference of the in situ chondron’s Poisson effect
under different magnitudes of compression. Fluorescence immunolabeling for type VI collagen was used to
identify the pericellular matrix (PCM) and chondron, and a series of fluorescent confocal images were
recorded and reconstructed to form quantitative three-dimensional models. The zonal variations in the
mechanical response of the chondron do not appear to be due to zonal differences in PCM properties, but
rather seem to result from significant inhomogeneities in relative stiffnesses of the extracellular matrix
(ECM) and PCM with depth.
Crosslinked Gelatin Nanofibers and their Potential for Tissue Engineering
Authors: Kim Young Jin , Kwon Oh Hyeong
Published: March 2009

Gelatin nanofibers were obtained by the use of TFE/deionized water co-solvent system
without adding any other fiber forming material. The diameter of nanofibers was in the rage from
200 to 360 nm. The water-resistant ability and mechanical properties of electrospun gelatin
nanofibers were improved by crosslinking in GTA or FA vapor, which increased with crosslinking
time. Cytotoxicity evaluation indicates that the crosslinked gelatin membranes support the
proliferation of human dermal fibroblast.
High Hepatic Function Was Maintained on Electrospun Nanofibrous Scaffold
Authors: Ahn Chang Hyun , Kim Young Jin , Kang Inn Kyu , Jun Ga Young , Ko Young Gwang , Yoon Kwan Han , Kwon Oh Hyeong
Published: March 2009

In this study, we prepared polystyrene (PS) nanofibers as hepatocytes culture substrates
by electrospinning method and subsequently coated with specific ligand (poly(N--vinylbenzyl--
β-D-galactopyranosyl-(14)-D-gluconamide)(PVLA) for hepatocytes attachment. Rat hepatocytes’
behavior on the PVLA-coated and non-coated PS nanofibrous matrices have been investigated.
Electrospun PS fiber structures revealed randomly aligned fibers with average diameter of 500 nm.
Fabricated PS nanofibers had no bonding points like cotton fibers. Analyses by ATR/FTIR and
ESCA revealed that PVLA was successfully coated to the surfaces of PS nanofibers. More
hepatocytes were attached on the surface of PS nanofibers coated with PVLA than that on noncoated
PS nanofibers. PS nanofibrous matrix could incorporate many cells into the interior of the
matrix probably due to the suitable pore size. Cell viabilities cultured on PVLA-coated PS
nanofibrous mats were maintained for 2 weeks, while it was decreased rapidly on PVLA-coated PS
dishes. High hepatic function especially albumin secretion was maintained for 2 weeks on
nanofibrous mats but rapidly decreased on flat PS dishes. These results indicate that nanofibrous
structure enabled spheroid-like culture results in providing cell-cell communication and subsequent
long-term maintenance of specific cell function.
Fibroblasts-Populated Fibrin Membrane Enhance Wound Closure
Authors: Yang Young Il , Seo Ji Yeon , Jeung Seung Jo
Published: March 2009

New strategies to make cultured fibroblasts grafts more appealing are aimed at reducing
the time spent in culture and improving the handling and biologic properties. In the present study,
we developed a simple and effective method to fabricate dermal fibroblasts-populated membrane
based on (1) the use of fibrin as a 3-dimensional matrix and (2) the use of cell- mediate contraction
to make a self assembled, detachable cells-populated membrane. Human dermal fibroblasts were
cultured by explants method. The fibroblasts encapsulated in fibrin were transferred into 6-well
culture plates which pretreated with Sigmacoat® to prevent cell binding on surface of culture dish.
Fibroblasts populated fibrin matrix (FPFM) was cultured in attached condition for 7 days and in
free floating condition for 1 day. The FPFM were contracted, spontaneously released from culture
plate, compacted, and formed tissue-like membrane. The fabricated FPFM revealed uniformly
distributed cells and newly synthesized extracellular matrix was deposited in matrix. FPFM could
successfully graft into full-thickness cutaneous defect of nude mice, and showed significantly
increased wound closure rate. Our results demonstrate that the FPFM membrane delivery system
allows for restoration of both the epidermal and dermal compartments.
In Vitro Chondrocyte Culture Using Hydrophilized PLLA Scaffold in Bioreactor System
Authors: Yang Hee Seok , Park Kwi Deok , Kim Byoung Soo , Kim Jae Jin , Ahn Kwang Duk , Han Dong Keun
Published: March 2009

Nonporous PLLA film and porous PLLA scaffolds were prepared and then grafted with
acrylic acid (AA) using in situ direct plasma treatment to obtain PLLA-g-PAA. Chondrocytes
isolated from rabbit knee articular cartilages were cultivated in Dulbecco’s modified eagle medium-
F12 (DMEM-F12) containing 10% fetal bovine serum (FBS) and 1% antibiotics and passaged twice
before cell seeding. Once seeded on either PLLA films or scaffolds, they were placed in a
bioreactor system and an intermittent hydrodynamic pressure (IHP) was applied in 3 bars, while
turned on for 2 min and off for 28 min during 15-day culture. AA grafting to PLLA surface was
confirmed from various surface analyses. From WST-1 assay, chondrocyte proliferation was
significantly improved with dynamic IHP for PLLA and PLLA-g-PAA scaffolds as compared to
static culture. This study indicates that IHP may have significant influence on chondrocytes
behavior in 3D culture environment.
In-Stent Restenosis in the Rabbit Common Carotid Arteries Organ Culture
Authors: Zhang Hai Yan , Zhao An Sha , Fan Shan , Chen Jun Ying , Huang Nan
Published: March 2009

In-stent restenosis is the result of a healing process that induces neointimal hyperplasia
though mechanisms that are still not understood. The purpose of this study was to analyze the early
histologic consequences and the kinetics of the healing process for a 72-hours period after stent
implantation in an organ culture model. MTT-tests show that the vessel could maintain activity in
the organ culture system. The vessel with stent had a different morphology and inflammatory
molecule release compared with the normal vessel. So there could have direct relationships between
inflammatory release and neointimal hyperplasia. The organ culture system can provide valuable
information for studies of in-stent restenosis after stent implantation, especially for evaluation of
new stents, such as drug-coated or other surface-modified stents.
Chondrogenic Differentiation of Human Adipose-Derived Stem Cells in PLGA (Poly(Lactic-Co-Glycolic Acid) Scaffold
Authors: Rhie Jong Won , Cho Hyun Mi , Lee Hee Young , Han Dong Keun
Published: March 2009

Human adipose tissue contain a population of pluripotent stem cells capable of
differentiating along multiple mesenchymal cell lineages. The goal of this study was to examine the
chondrogenic potential of adipose-derived stem (ADS) cells. ADS cells were isolated from human
subcutaneous adipose tissue obtained by lipectomy and liposuction, and were expanded and grown
in vitro with or without chondrogenic medium in micromass culture condition and 3D culture
condition in PLGA(poly(lactic-co-glycolic acid)) scaffold. Human ADS cells of micromass
culture condition and 3D culture condition in PLGA scaffolds, were differentiated with
chondrogenic medium consisted of transforming growth factor-β1, insulin-transferrin-selenium,
dexamethasone and ascorbate-2-phosphate. ADS cells abundantly synthesized cartilage matrix
molecules including collagen type II, VI and link protein. ADS cells under high-density micromass
culture condition with chondrogenic medium formed well defined nodules within 48 hours of
induction. On the 3rd week after chondrogenic differentiation of ADS cells under the micromass
culture condition and 3D culture condition of PLGA scaffold, mRNA of type II collagen, type VI
collagen and link protein were expressed by reverse transcription polymerase chain reaction
(RT-PCR). On the 3weeks, content of glycosaminoglycan in cells treated with chondrogenic
medium was greater than that with non chondrogenic medium(control).On the 3rd week culture
under the chondrogenic medium, hematoxylin & eosin (H & E) staining, alcian blue staining
and type II collagen immunohistochemistry analysis confirmed the chondrogenic differentiation in
micromass and 3D cultured specimen. These findings document the ability of ADS cells to produce
characteristic cartilage matrix molecules, and provide the possibility of cartilage regeneration for
cartilage substitution.
Implantation of Cultured Preadipocyte Using Chitosan/Alginate Sponge
Authors: Rhie Jong Won , Song Jin Kyung , Lee Paik Kwon , Ahn Sang Tae
Published: March 2009

Alginate was a proven biocompatible biomatrice for cells but it was known not to provide
a proper microenvironment needed for the proliferation of cells because of its anionic property,
which caused its low affinity for cells. Water-soluble chitosan was well known as wound healing
material and it also had cationic property which helped cell-to-matrix adhesion. The purpose of this
study is to assess the ability of a chitosan/alginate mixed sponge as a scaffold for preadipocytes to
serve as a biological implant for soft tissue augmentation. Chitosan/alginate and calcium alginate
sponges were made by lyophilizing of alginate with water-soluble chitosan mixture and
with calcium chloride mixture, respectively, and those were observed by SEM. Preadipocytes
seeded in those sponges were cultured for 2 weeks. In vivo study was designed that
chitosan/alginate sponges with and without preadipocytes were implanted subcutaneously into nude
mouse. Chitosan/alginate and calcium alginate sponges which had highly porosity and 50-200㎛
pore size. In the chitosan/alginate sponge, the levels of DNA amount were significantly higher than
those in calcium alginate sponge (P<0.05). In both groups, they increased progressively with time.
On the in vivo study, it was observed that adipose tissue layer in the margin of chitosan/alginate
sponge on the 2 weeks after implantation of nude mouse. On the 8 weeks after implantation, thick
layer of adipose tissue and neovascularization were observed in the chitosan/alginate sponge.
Consequently, chitosan/alginate sponge provided proper microenvironment to human preadipocyte,
increased the cell proliferation and maintained the pore that offered neovascularization, so turned
out to be effective form of fat transplantation for soft tissue augmentation and reconstruction.
Novel Poly(Ester Amine) Based on Polycaprolactone and Polyethylenimine as a Gene Carrier: Effect of Hydrophobicity on Transfection Efficiency and Cytotoxicity
Authors: Arote Rohidas B. , Kim Tae Hee , Kim You Kyoung , Jere Dhananjay , Jiang Hu Lin , Park In Young , Cho Myung Haing , Nah Jae Woon , Cho Chong Su
Published: March 2009

Novel, biodegradable poly(ester amine)s (PEAs) were synthesized using hydrophobic
polycaprolactone diacrylate (PCLDA) and highly cationic polyethylenimine (PEI). This novel gene
carrier can form stable DNA complexes with particle sizes around 200 nm, and showing excellent
transfection efficiency and relatively low cytotoxicity compared with PEI 25K. Effect of
hydrophobicity on transfection efficiency and cytotoxicity was profound and was relatively
important parameter for the success of gene delivery.
Effect of Solvent on Porous PLA/HA Scaffolds Preparation Using Novel Solid H2O2 Porogen
Authors: Wang Yi , Fan Hong Song , Wen Xian Tao , Xiao Yu Mei , Gu Zhong Wei , Zhang Xing Dong
Published: March 2009

Hydroxyapatite/polymer scaffolds with proper biomechanical properties and stable 3-D
porous structure were fabricated by combining gas foaming with solvent-casting/particle-leaching
technique, in which novel solid H2O2 were used as a porogen. During the manufacturing process,
we found that the porosity, compressive strength and microstructure of the composites are varied
from each other while different solvents (dichloromethane, acetone, chloroform and 1,4-dioxane)
were used. Porosities of the specimens increase from 72±5 to 87±5% in accordance with the
increase of boiling point from 39.75 to 101.32 °C, while compressive strength decreased (4.8±0.7-
0.5±0.3 MPa). Interactions of HA/solvent and PLA/solvent together with evaporation dynamic tests
of different solvents were investigated. The results show that the evaporation rate of the solvents is
the most important factor affecting the final properties of the scaffolds.
Effect of Oxygen on Elastic Modulus and Mechanical Property of Metastable β TiNbO Based Alloys
Authors: Kim Won Yong , Kim Han Sol
Published: March 2009

Elastic modulus and mechanical property of Ti-Nb-O alloys prepared by arc melting and
subsequent water quenching were investigated in order to correlate the result of microstructural
observations and phase stability. In quenched state, it was evidently observed that the volume fraction
of bcc-structured β phase increased with increasing content of oxygen, and the occurrence of
intermediate ω phase was suppressed in the present Ti-Nb based alloys. This microstructural result
was supported by changes in martensite transformation temperature, which decreased with increasing
content of oxygen within the chemical composition range investigated. Therefore, it is suggested that
oxygen plays a role as a β phase stabilizer rather than α stabilizer in metastable β Ti-Nb alloys. Yield
strength increased with increasing content of oxygen without a large consumption of ductility in
Ti-Nb based alloys with Nb content of 24% while elongation value decreased with increasing content
of oxygen in Ti-Nb based alloys with Nb content of 28%. The variation of mechanical property was
explained by the phase stability, phase formation and microstructure in correlation with oxygen and
Nb content.
Tissue Regeneration of a Hybrid Vascular Graft Composed of Biodegradable Layers and Non-Biodegradable Layer by Static and Pulsatile Flows
Authors: Choi Yoon Jeong , Kim Mi Sook , Noh In Sup
Published: March 2009

Clinical applications of expanded polytetrafluoroethylene (ePTFE) as a small diameter
graft have been limited due to its limited patency rates, even though its demands are high. After
fabricating the biodegradable PLGA layers on both the inside and outside of ePTFE, long-term in
vitro smooth muscle cell culture was performed on the luminal scaffold surface. The fabricated
hybrid ePTFE scaffolds were designed to have three distinctive layers and porous structures in the
biodegradable layers generated by gas-foaming of the ammonium bicarbonate porogens, i.e. two
layers of poly(lactide-co-glycolide) (PLGA) as biodegradable layers for tissue engineering and an
ePTFE layer in the middle as a non-biodegradable layer. We evaluated the regenerated vascular
tissues after applying either static or pulstile flow on a smooth muscle cells-seeded hybrid scaffold.
Analysis of the engineered tissues was performed with SEM for morphological observation and
H&E staining for observation of tissue development dependent upon a mode of culture system, flow
patterns and scaffold species.
Growth of In2O3 Thin Films on Lithium Aluminum Oxide Using a Triethylindium and Oxygen Mixture
Authors: Kim Hyoun Woo , Lee Jong Woo , Han Jeong Whan , Kim Hyung Sun , Kim Mok Soon , Yoo Byung Don , Hwang Sun Keun
Published: March 2009

Indium oxide (In2O3) films were successfully grown on LiAlO2 substrates using the
triethylindium (TEI) as a precursor in the presence of oxygen in the metalorganic chemical vapor
deposition process. We have established the correlation between the substrate temperature and the
structural properties. The grain structures were clearly shown on the surface of the films deposited at
350°C. The root mean square (RMS) surface roughness of the In2O3 films increased with increasing
the substrate temperature. A photoluminescence measurement at room temperature exhibited a
yellow-green emission band centered at 585 nm.
Effect of Glass Phase on the Defect Formation during the Dissolution of Hydroxyapatite
Authors: Youn Sang Heum , Yang Z. X. , Hwang Kyu Hong , Lee Jong Kook , Yoon Seog Young
Published: March 2009

Particle separations occurred frequently in sintered hydroxyapatite when immersed
in distilled water or simulated body fluid. This dissolution initiated at grain boundary
creating nano-size defects such as small pores and grew up to micro scale by
increasing immersion time. The dissolution, probably due to the appearance of
secondary phases in grain boundary, resulted in grain separation at the surfaces and
finally in degradation and fracture. And the dissolution concentrated on those grains
adjacent to pores rather than those in the dense region.
Hydroxyapatite ceramics incorporated with calcium silicate glass were prepared by
slip casting to enhance the sinterability as well as to reduce dissolution. Glass phase
was incorporated into hydroxyapatite to act as sintering aids followed by
crystallization in order to improve the mechanical properties without reducing
biocompatibility. From dissolution test, significant damage was reduced even more
than 7 days and the dissolution pattern somewhat changed than pure hydroxyapatite.
X-ray diffraction and SEM showed no decomposition of secondary phases in grain
boundary and fracture toughness somewhat increased.
Effect of Ca/P Ratio on the Dissolution of Calcium Phosphate Powders
Authors: Lee Jong Kook , Song Dae Sung , Hwang Kyu Hong , Seo Dong Seok
Published: March 2009

Calcium phosphate ceramics (CPC) have been attractively used in different areas of
biomedical applications, such as substances of artificial hard tissue replacement implants, drug
delivery system due to their biocompatibility and bioactivity. In this work, three calcium phosphate
powders between Ca/P molar ratio 1.50-1.67 were synthesized by aqueous precipitation method,
using the mixture of Ca(NO3)2·4H2O and H3PO4 solutions to ammonia solution. During the
precipitation reaction, Ca/P molar ratio was adjusted by controlling pH of the solution between 8.0
and 10.5 by the addition of ammonium hydroxide solution. All powders were treated at 800 oC for 2
hrs. The calcined powders were immersed in pH 7.4 distilled water at 37°C for 3 and 7 days.
Decomposition and related dissolution with the various Ca/P ratios were investigated by XRD, FTIR,
and TEM observation.
Star-Shaped Poly (Γ-Caprolactone-b-Ethylene Glycol): Synthesis, Characterization and Aggregation Behavior
Authors: Fan Yu Jiang , Liang Jie , Chen Guo Ping , Tateishi Tetsuya , Gu Zhong Wei , Zhang Xing Dong
Published: March 2009

Linear and Star-shaped PCL-b-PEG copolymers were synthesized through a two step process,
including the first step to synthesize the star-shaped PCL through ring-opening polymerization of
Γ-caprolactone initiated from multi-functional alcohol under the existence of tin(II) ethylhexanoate
[Sn(Oct)2] catalyst, and the following step to couple the obtained star-shaped PCL with PEG
segments using bi-functional linker. The structure of the polymers was confirmed by IR, NMR,
GPC, et al. The aggregation behaviors of the star-shape copolymers were compared with that of the
linear block copolymer with corresponding molecular weight of each arm, and the influences of
structure factors were discussed.
Preparation of Silk Fibroin/Bacterial Cellulose Composite Films and their Mechanical Properties
Authors: Jung Rira , Jin Hyoung Joon
Published: March 2009

We prepared composite films consisting of two biocompatible materials, bacterial
cellulose and silk fibroin. Aqueous silk fibroin solution and bacterial cellulose excreted by
Acetobacter xylinum were used to fabricate the composite films. It was verified by field emission
scanning electron microscopy and X-ray diffraction that the two components were finely blended
and that the silk fibroin was crystallized during the composition of the films. The silk fibroin
penetrated well between the individual fibrils of the bacterial cellulose, while the water molecules
inside the pellicular bacterial cellulose were evaporating. The composite films did not dissolve in
water due to the crystallization of the silk fibroin in the composite films. We also observed the
change in the mechanical properties of the composite films according to the water content. The
composite films became more flexible and tougher when they were dipped in water, whereas they
were very brittle in the dehydrated state.
Antibacterial Polyurethane Organosilicate Nanocomposites
Authors: Styan K. , Abrahamian M. , Hume E. , Poole-Warren L.A.
Published: March 2009

Thermoplastic polyurethanes are versatile polymers much used for biomedical
applications due to their mechanical properties and biocompatibility. Like most implantable
materials they are susceptible to bacterial colonization, particularly in applications at high risk of
bacterial contamination such as percutaneous catheters. The objective of this study was to assess
the antibacterial activity and the cell responses to a series of nanocomposite variants fabricated from
a polyether polyurethane and organically modified silicates containing either antibacterial
dispersing agents, non-antibacterial dispersing agents, or combinations of the two. The results
suggest that co-modification is a promising approach for modulating both bacterial and mammalian
cell responses to achieve appropriate antibacterial properties without cell inhibition.