bluuebunny/crossref_metadata_2025 huggingface dataset:
The Construction of Xi'an Overall Water Environment Based on the Eco-Permeable Transformation of City Hardened Surface
Authors: Yu Dong Fei , Zheng Qiao
Published: October 2011

Modern urban surface is gradually covered by water blocking material in China, it has been increasing the city and its surrounding areas on the ecological significance of the "man-made desert" effect. In this paper, taking Xi'an as an example, the authors discuss the possibility to build a whole city water environment through the transformation of city hardened of surface. Xi'an has obvious characteristics of seasonal rainfall, taking the transforming of city's eco-permeable surface as a starting point, will contribute to the gradual recovery of the city’s function as an ecological nodes and the basic "metabolism"; restoration and reconstruction of urban water environment, improving the living environment, highlighting the "Chang’an eight water" pattern and context features of the city.
The Analysis and Research on Electromagnetic Radiation Pollution of High Voltage Transmission Line
Authors: Lu Di , Wang Jian Xin
Published: October 2011

With the development of China's power industry, many cities had renovated, expanded electricity power network ,110、220 kV and above the high voltage overhead transmission lines all around the urban areas and residential areas. As the electromagnetic radiation of high-voltage transmission lines inevitability pollute on urban environment, according to the Investigation, monitoring and analysis of high voltage, based on national standard of electromagnetic radiation, this paper proposed the controlling measures and recommendations of electromagnetic radiation. Therefore, the research that the electromagnetic radiation impact on the environmental has a very high value and academic significance.
A Study on Light-Transporting Principle of Seamless Prism Light Guide
Authors: Li Wei , Chen Qian Yi , Na Yan Ling
Published: October 2011

A new kind of prism light guide is introduced in this paper. The guide is seamless and made by extruding technique, which makes it has lower cost. The cost of the guide is only about 15% of the price of prism films. The guide transport light by total internal reflection and the light-transporting principle is described in detail in this paper. In theory all light would be transported by the process of total internal reflection but irregularities in the guide cause a small proportion of light to leak out the guide. This effect can make the guide glow and for this reason the seamless prism light guide acts as both a light transport and emission device. The guide can be used in lighting or daylighting of underground buildings and windowless buildings, or buildings in which inflammable and explosive products are manufactured. It can also be used in nightscape lighting as a decorative lighting fixture. In this paper, the application of the guide in a concrete-curing room is introduced briefly.
Startup of Denitrification Bioreactor and Influence of Temperature and DO for Treatment
Authors: Li Ya Feng , Liu Jia Yuan , Zhang Yan
Published: October 2011

The sewage is used for startup and stable operation of the test, Startup in simultaneous nitrification-denitrification of Denitrification Bioreactor and Influence of Temperature and DO for Treatment was studied in the test. The results showed that, When the temperature was 30 degree Celsius, DO was 0.3-0.5mg/L，pH was 8 and reflux ratio was 300%, the removal rate of COD,ammonia nitrogen and total nitrogen reached stability after domestication of 58 days, and the quality of effluent achieved the A national standard. There is small influence of temperature for COD removal and large influence of temperature for ammonia nitrogen removal. Biological nitrogen removal process was not fit to operate in low temperature, and the suitable temperature was from 20 degree Celsius to35 degree Celsius. With DO increasing, the removal rates of COD and NH4+-N was increasing and then kept in a constant value. When DO was 0.4 mg/L, the removal rate of TN reached the maximum and it was 75.86%
Pilot Study on Dosing Suspended Fillers to Alleviate Membrane Fouling
Authors: Yu Gai Jing , Liu Zhi Qiang , Zhang Zhi Hua , Chen Xiu Bo , Li Xiao Jing
Published: October 2011

In this article, Vertical A/O-MBR was used as the experimental device to study membrane fouling through dosing cylindrical rigid suspended fillers, and the best conditions for membrane fouling control and effluent quality with fillers was discussed. Results showed that the critical flux zone decreased. When the MLSS was 5g/L and the suspended fillers dose was 1%, 5%, 10%, respectively, TMP increased rapidly with the quantity, greater quantity of fillers speeded up the membrane fouling process, and in small quantity membrane fouling had some delay action. The best dosing of fillers was determined as 7% in the condition of MLSS=5g/L, and the effluent quality was good.
Thermodynamics of Fluoride Adsorption onto Magnesia-Amended Activated Carbon
Authors: He Zhi Li
Published: October 2011

Removal of fluoride from drinking water using magnesia-amended activated carbon (MgO-AC) was investigated. The MgO-AC was characterized scanning electron microscope (SEM). Attempts were made to fit the isothermal data using Langmuir and Freundlich equations. The experimental results have demonstrated that the equilibrium data are fitted well by a Langmuir isotherm model and the maximum sorption capacity of fluoride evaluated is 7.22 mg/g. Thermodynamic parameters of ∆G0, ∆H0 and ∆S0 show that the adsorption is a spontaneous and endothermic process.
Characterization of Al-Humic Complexation and Coagulation Mechanism
Authors: Jin Peng Kang , Ren Wu Ang , Wang Xiao Chang C.
Published: October 2011

Using fluorescence and optical monitoring techniques, the process of coagulation of natural humic acids (HA) was studied paying attention to the interaction of aluminium and HA. Experiments were conducted using a jar tester equipped with a PDA2000 monitoring device for online monitoring of the Al-humic coagulation process. After flash mixing, slow mixing and settling, the supernatant was collected for fluorescence analysis to measure the concentration of residual aluminium which has not reacted with HA molecules. The process of aluminium hydrolysis was also studied by online monitoring of the formation of ‘alum flocs’ in a solution free from HA. Electrophoretic analysis and TOC measurement were conducted respectively for evaluating the condition of charge neutralization and HA removal. On this basis, the mechanism of Al-humic coagulation was discussed. It can be concluded that at pH 5, charge-neutralization and co-precipitation is the main mechanisms of coagulation, while at pH 7 the main hydrolyzed species are precipitated aluminum hydroxides so that sweep flocculation becomes the main mechanism of coagulation as well as overdosing at pH 5.0.
Numerical Simulation Using FE-SPH Method for Concrete Slabs Penetrated and Perforated by Steel Projectiles
Authors: Xiong Yi Bo , Chen Jian Jie , Hu Yong Le , Wang Feng Chao
Published: October 2011

The explicit dynamic code LS-DYNA3D is used to simulate limited-thickness concrete slabs penetrated and perforated by steel projectiles with velocities from 381 m/s to 1058 m/s. The concrete slab is modeled with Smooth Particle Hydrodynamics (SPH) elements near the trajectory while Finite Element Method (FEM) elements in the others of the target, which is called FE-SPH method. The elastic-plastic model and Johnson-Holmquist concrete model are used to describe the mechanical behaviors of the projectiles and target slabs, respectively. The residual velocities computed by both FEM and FE-SPH method agree well with those of experimental results. For brittle concrete, the penetration and perforation phenomenon modeled by FE-SPH are in closer agreement with the experimental results than those modeled by FEM. Simulation of penetration and perforation by FEM require artificial element erosion set, which would lead to distortion of modeled results.
Effects of Restraint Condition on Carbonation of Concrete Containing Expansive Agent
Authors: Tu Liu Qing , Shui Zhong He , Xu Wen Bing , Chen Wei , Ma Jun Tao
Published: October 2011

The concrete containing expansive agent, when limited, is affected by the addition of expansive admixture much, which influence the carbonation resistance. This article makes a comparison with anti-carbonation ability of concrete under restraint and non-restraint condition. The compressive strength and carbonation depth are tested, and the changes of micro-structure are also analyzed with TG-DSC and MIP analysis. The results reveal that single-dimensional restraint condition can efficiently improve the pore structure of concrete. And expansive agent also has a slight improvement to it. Single-dimensional restraint condition can obviously enhance the anti-carbonation ability of concrete containing expansive agent.
Analysis of Tunnel Rock’s Dynamic Stress with Input of Different Peak Ground Motions
Authors: Sun You Wei , Men Ni , Bo Jing Shan , Li Ping , Cai Xiao Guang
Published: October 2011

The changes of tunnel rock stress caused by dynamic load is a hot point in geotechnical engineering. The paper introduces seismic methods of seismic design codes in China. The paper select state road 318(Huangcaoping part)as an example. Using finite difference software to analyze the rock pressure changes around the lining-tunnel with different seismic inputs. Comparing the results the rock static pressure and find the relative amplification factor between dynamic pressure and static pressure. Based on the results of analysis, we can obtain the following conclusions: As the peak ground motion acceleration increases, the peak value of tunnel rock increases, too. The amplifications change in a small range. The oblique parts of tunnel are the weakest parts of the tunnels. In different areas, the amplifications change a lot. The maximum ones are in the area of oblique.
Applying Research on Testing Technique of High Performance Concrete
Authors: Wang Zheng Jun , Han Mei , Zhao Felix
Published: October 2011

In order to master timely and accurately construction quality of high performance concrete, detection of compressive strength of high performance concrete can be tested non-destructively, rapidly and accurately. The paper did preliminary research on high performance concrete with redound method, furthermore, it established estimation model between rebound value and compressive strength. Experiment shows that rebound method can effetely test compressive strength of high performance concrete. Construction quality of Cement concrete structure or component can timely grasped in period of construction with the method.
Scientific Location between Rail Transit and Bus in China
Authors: Wang Yu Ping , Zhao Li , Ma Chao Qun , Guo Yan Yong
Published: October 2011

With the rising of urban rail transit planning and constructing in China, the relationship between rail transit and bus must be located. After analyzed the inevitability of competition and the necessity of cooperation between rail transit and bus, this paper strategically located the relationship between rail transit and bus. At last, based on the characteristic of competition between rail transit and bus, this paper brought forward specific measures of staggering competition with cooperation corresponding to different rail transit develop stage to implement rail transit and bus. Higher level competition will be formed, and the competition result is not “single win” but “both win”.
Research on the Consolidation Theory of Sand Drain Foundation Settlement
Authors: Pan Wei Dong , Sheng Xiao Long , Gu Ren Guo , Zhu Ke
Published: October 2011

In the consolidation theory of sand drain foundation settlement, the influence of groundwater level changes on the soil consolidation has been paid less attention. Therefore, discussing those changes' influence will help to deepen and perfect the sand drain consolidation theory. Through theoretical research and field measurements, the concrete influences of water level weight, dissipation rate and other factors on the consolidation process are obtained. This helps to improve the consolidation theory and efficiency.
Research on Stability of Pressure Bars under the Function of Lateral Centralism Load
Authors: Li Zi Lin , Gao Yu Bin , Wang Xue Song
Published: October 2011

To ensure the pressure bars to work safely and reliably, the most important thing is that the bars should possess sufficient stability. The previous massive domestic and foreign literature is just about the instability of the pressure bars under the function of longitudinal critical force, the research on the instability under action of the lateral critical force is seldom. So the research on the stability under the function of the lateral critical force is of great importance. This paper deduces the formula of the lateral critical force with the energy method for the first time when the pressure bars is in the condition of instability, and the formula has good reference value for the research on instability of the pressure bars under the lateral critical force.
A New Health Monitoring System for Cable-Stayed Bridges II: Applications
Authors: Luo Ling , Luo Hong , Du Bai Song
Published: October 2011

In the companion paper, a new health monitoring system with five sub-systems is proposed for cable-stayed bridges. In this paper, for a health monitoring system of the cable-stayed bridge, it is classified four levels as excellent, good, fair, and poor base on the function of the system at the first time. The monitoring systems of the second Wujiang Bridge, a cable-stayed bridge with a low tower and a high tower, and the Shibangou Yangtze River Bridge, a cable-stayed bridge with regular double towers, are employed as two examples to narrate the determination of the monitoring parameters, monitoring contents and methods, the principles of the positions of measuring points, and evaluation of the system grade. The health monitoring system for the cable-stayed bridge sets up a good example for other types of bridges and has a reference value for the development of the bridge health monitoring systems.
Hourglass Control Methods in Numerical Simulation Code RingForm
Authors: Zhang Xue Bin , Wan Qiong , Li Zhi Gang
Published: October 2011

Hourglass is obviously aroused in cold ring rolling simulation with reduced integration element because of ring vibrating violently and small contact area of ring and rollers. In the developed numerical simulation code named RingForm, two methods are used to control the hourglass. The first method is combination of artificial damping and artificial stiffness. The second is one-point quadrature element with hourglass control, which need not user-defined control parameters. Hourglass energy can be reduced to 3 percent of the internal energy. Using the latter, good elements are acquired, while computational efficiency is obviously lower than the former.
Simulation Researches of Angular Displacement Control System with Constant Vertical Wind Disturbance
Authors: Qu Dong Cai , Yu Jin Yong , Cheng Ji Hong
Published: October 2011

Constant vertical wind disturbance is a kind of important disturbance form. This form will bring big effect on keeping and controlling aero attitude angle and altitude. Based on established aero sport mathematics models with constant vertical wind disturbance, the structure principle diagram of aero angular displacement control system is founded. Based on MATLAB, simulation researches were emphases done on performance influence of aero angular displacement control system by different disturbance wind speed and disturbance time length. Simulation results show: aerocraft control system performance is greater impacted on constant vertical wind disturbance.
Strength Properties of Sludge Solidified with Fly Coal Ash and Portland Cement
Authors: Daněk Tomáš , Thomas Jan , Mališ Jiří , Jelínek Jan
Published: October 2011

The paper deals with the properties of mixtures on the base of fly ash and sludge from the metallurgical production. The mixture composition of this group is grounded in the knowledge acquired during testing of various mixtures. The mixtures of sludge and coal fly ash and/or cement after of curing were used for tests. The uniaxial compressive strength of solidified sludge was examined. To understand the behaviour of mixtures in the long term, the prepared mixtures were tested after 14, 28, 56 and 120 days.
Performance of Optical Wavelength Demultiplexer Based on Silicon-on-Insulator (SOI) Microring Resonators (MRRs)
Authors: Hazura H. , Hanim A.R. , Mardiana B. , Shaari S. , Majlis B.Y. , Menon P.S.
Published: October 2011

In this paper, we presented the performance analysis of Silicon- on- Insulator (SOI) based, four channels optical wavelength demultiplexer using microrings. The characterizations are done employing Finite- Difference Time- Domain (FDTD) mode simulations from RSOFT. Serially cascaded microring arrays up to the third order are demonstrated to discuss the design issues of the laterally coupled wavelength demultiplexer. Characteristics like the Free Spectral Range (FSR), crosstalk and insertion loss losses are studied.
Comparison of Mechanical Properties between Thai Orthodontic Elastics with Different Ammonia Contents and Commercial Orthodontic Elastics
Authors: Anuwongnukroh N. , Senarak Porntiwa , Dechkunakorn Surachai , Suddhasthira Theeralaksna , Kongkaew C. , Loykulnant Surapich , Wichai Wassana , Jitboon Sopita
Published: October 2011

Introduction: The most widely used preservative system for natural rubber latex to date is the ammonia-based system preventing spontaneous coagulation and putrefaction due mainly to bacteria contamination. Objectives: The study compared 2 types of Thai orthodontic elastics, produced from natural rubber latex with different ammonia contents with commercial orthodontic elastics in terms of initial extension force, residual force, force loss, swelling index, breaking strength and maximum displacement. Materials and Methods: Thai orthodontic elastics were developed from 2 types of natural rubber latex; low ammonia < 0.15% (Thai-L), and high ammonia not < 0.6% (Thai-H). The mechanical properties of Thai orthodontic elastics were compared with commercial elastics (Ormco). Mechanical properties were tested using a universal testing machine (Instron 5566). Data were analyzed by One-way ANOVA and Tukey’s test compared the measurements among groups. Results: Ormco had the highest initial extension force and showed significant differences with Thai-L and Thai-H. Thai-L had the highest residual force but showed no significant difference compared with Ormco. Thai-L had the lowest percent of force loss and showed significant differences with Thai-H and Ormco. Thai-L had lower force loss than Thai-H. For swelling index, Thai-L had the highest elasticity. For breaking strength and maximum displacement, both Thai elastics met the Australian Standard (AS) for breaking strength and maximum displacement, similar to Ormco elastics. Conclusion: All elastics met the specifications of the AS for breaking strength and maximum displacement. Thai-L had comparable properties with commercial orthodontic elastics in terms of mechanical properties. Thai-L had comparable properties with Ormco in terms of mechanical properties and may be developed for orthodontic purposes.
Magnetic Phase Transitions in Ultrathin Films of Different Crystal Structures
Authors: Afremov Leonid , Kirienko Yury
Published: October 2011

The properties of ultrathin films have been studied within the framework of Ising model and the method of random-field interactions. It is shown that the Curie temperature is inversely proportional to the number of layers. Critical exponent has been obtained and it is shown that it does not depend on the type of crystalline lattice.
Microstructural Evolution during Accumulative Roll-Bonding Process of a High Performance Copper Alloy
Authors: Lee Seong Hee , Yoon Daejin , Utsunomiya Hiroshi
Published: October 2011

Microstructural evolution of a copper alloy processed by accumulative roll-bonding (ARB) was investigated by EBSD analysis. The grains became thinner and elongated to the rolling direction with increasing the number of ARB cycles. The subdivision of the grains to the rolling direction actively begins to occur after 5 cycles of the ARB, resulting in formation of ultrafine grains with small aspect ratio. After 8 cycles, the ultrafine grained structure with the average grain diameter of 250nm developed in almost whole regions of the sample. In addition, the fraction of high-angle grain boundaries increased with the number of ARB cycles and reached about 0.7 after 8 cycles. The texture development of the ARB processed samples was different depending on the number of ARB cycles and the positions in the thickness.
The Patch Test of Numerical Manifold Schemes with Mixed Cover Coupled Velocity and Pressure for Steady N-S Equations
Authors: Chen Shu Ping , Zhang Zheng Rong , Yan Jin Hua
Published: October 2011

In numerical manifold schemes for direct solution of steady Navier-Stokes equations, mixed cover for velocity and pressure was adopted in finite element cover system. The patch test of numerical schemes was investigated, mixed cover manifold element has been proved to meet the stability conditions, and can be applied to directly solve Navier-Stokes equations coupled velocity and pressure. As an application, the numerical manifold schemes were used to simulate the steady flow past a step. Numerical solutions illustrate the stability of numerical manifold schemes, and it indicates that manifold method is an effective numerical method for steady Navier-Stokes equations.
Influence of Sn Content on the Mechanical and Corrosion Behavior of AM60 Base Alloys
Authors: Kim Jeong Min , Park Joon Sik , Kim Ki Tae
Published: October 2011

The effects of Sn addition on the cast microstructure, mechanical properties, and corrosion behavior were comprehensively investigated. Cast AM60 alloy mainly consisted of primary Mg matrix and Mg17Al12 phase, and the microstructure virtually remained unchanged by the Sn additions up to 2%. Most of added Sn solute atoms were observed to dissolve into the Mg17Al12 phase and only a few fine MgAlSn precipitates were found in the high Sn alloys. Tensile strength at both room and 175oC was rather deteriorated by increasing Sn content, however the creep strength was significantly enhanced by it. Polarization characteristics of cast AM60 based alloys were not remarkably affected by the Sn content.
The Equilibrium between Calcite and Apatite Precipitation onto Bioglass from Three Different Aqueous Media
Authors: Lazaro Gilderman Silva , Santos Silmara Caldas , Almeida Luiz Eduardo , Barreto Ledjane Silva , Araujo dos Santos Euler
Published: October 2011

It has been reported that there is a slight equilibrium between calcite and apatite precipitation from SBF solution during typical bioactivity assays, once it is supersaturating in both ionic precursors. In order to better understand this mechanism, we have proposed here to evaluate the role of three different aqueous medium (water, SBF and McCoy), under equilibrium (agitation) and out of equilibrium (no agitation).
Fabrication of βTCP with Fully-Interconnected Porous Structure
Authors: Nikaido Taro , Tsuru Kanji , Daitou Fumikazu , Munar Melvin L. , Matsuya Shigeki , Nakamura Seiji , Kunio Ishikawa
Published: October 2011

Calcium phosphate foam could be an ideal bone filler and scaffold for tissue engineering. This paper describes fabrication method of β-tricalcium phosphate (βTCP) foam with fully-interconnected porous structure by employing magnesium oxide (MgO) as βTCP stabilizer. The foam was prepared using the so-called ceramics foam method. MgO was added to calcium carbonate and dicalcium phosphate dihydrate so that 0, 1, 2, 3, 4, 6 and 8 mol% calcium would be substituted by magnesium (Mg) in βTCP structure. After sintering at 1500°C, crystal phase of the obtained foam included α-tricalcium phosphate (αTCP) when no Mgor less than 3 mol% Mg was added. In contrast, crystal phase was single phase βTCP when 3 mol% or higher Mg was added. The compressive strength was approximately 15 kPa and the porosity was above 95% for all specimens. No significant difference was observed between αTCP and βTCP foams in compressive strength and porosity when the sintering temperature was the same.
Fabrication of Carbonate Apatite Block from Calcium Sulfate by Hydrothermal Treatment
Authors: Nomura Shunsuke , Tsuru Kanji , Valanezhad Alireza , Matsuya Shigeki , Takahashi Ichiro , Kunio Ishikawa
Published: October 2011

Carbonate apatite (CO3Ap) is expected to be an ideal bone substitute since it can harmonize with the bone remodeling cycle. The aim of this study is to fabricate a CO3Ap bone substitute from gypsum (calcium sulfate, CaSO4·2H2O) hardening bodies based on dissolution-precipitation reaction. Calcium sulfate hemihydrate mixed with water at a water-to-powder ratio of 0.5 was packed in a split stainless mold and kept at room temperature for 24 hours to obtain set CaSO4·2H2O. The set CaSO4·2H2O was hydrothermally treated in the presence of disodium hydrogen phosphate (Na2HPO4) and sodium hydrogen carbonate (NaHCO3). The results of powder X-ray diffraction and Fourier transform infrared spectroscopy indicated that CO3Ap block could be fabricated from the set CaSO4·2H2O block by hydrothermal treatment with Na2HPO4 and NaHCO3. When the treatment temperature was increased, the conversion rate to CO3Ap increased. However, the carbonate content decreased with increasing treatment temperature.
Effect of Simulated Body Fluid on the Behaviour of Artificial Bone Composite Material Extended by Hydroxyapatite and Silicate Powders
Authors: Yücel Sevil , Aydin Ismail , Özçimen Didem , Tekerek Bilge Sema , Yıldırım Özlem , Kabakcı Aycan
Published: October 2011

Bone matrix consists of organic and inorganic components. Organic phase mainly contributes to flexibility of bone while inorganic phase being responsible for the rigidity and hardness of the bone. Due to the biocompatibility of ceramics many forms of them have been used as the bone replacement and as the repair material. Hydroxyapatite which also exists in the natural structure of bone is one of those ceramics used as a component of bone cement. In order to modify the physical properties of prepared bone composite structures, some additives are included within the structure. In this study, a silicate material is included as an inorganic filler together with hydroxyapatite. Bis-GMA and HEMA were used as organic matrix. The prepared composites were than immersed in SBF and FTIR, SEM, hardness analyses were performed on the samples before and after the immersion. The results were reported in later part. It was observed that the precipitation of hydroxyapatite occurred after the immersion of samples in SBF and the hardness values were increased for each sample.
Evaluation of TCP Loaded Clinoptilolite Use as Graft Material on Rabbit Tibia
Authors: Uyumaz A.N. , Ozyegin L.S. , Buyukakyuz N. , Yesilbek B. , Oktar F.N.
Published: October 2011

Clinoptilolite mineral which is a member of zeolite family has been recently used in medical and dental applications. Until today, it has never been used as a graft material. In the present study tricalcium phosphate (TCP) imbued 90-95% pure clinoptilolite was used as graft in rabbit tibia. General anesthesia was accomplished using intra muscular (IM) injections of Xylazin and Ketamine HCL. TCP imbued clinoptilolite was placed in the defects created in the tibias of the subjects. Control group defects were left empty. One group was sacrificed on day 28 and the other group on day 56 to evaluate osteogenesis, residual graft material, inflammation and fibrosis. Histological evaluation revealed new bone formation at 28 days to be 14/7 at control group where as its 11/7 for the experimental graft group. At 56 days the values are as 18/7 for control and 14/7 for the experimental graft groups (n = 7). Our study group is the first to perform intrabony application of clinoptilolite. No evidence of abnormal inflammatory cell formation or fibrosis was witnessed in groups. When TCP, which can be used as a standalone graft material, was mixed with zeolite it was not as effective as expected. We believe that, TCP particles are absorbed and captivated in the initial phase and due to absorption strength of zeolite cannot be released back to the environment. We assume its effect can increase with longer time periods. Bone formation without infection is observed around graft particles. Based on the present study, since clinoptilolite does not provoke an inflammatory process, its use in unison with TCP can provide a supporting structure in defects.
Recrystallization of Amorphized α-TCP
Authors: Döbelin Nicola , Galea Laëtitia , Eggenberger Urs , Ferreira José Maria da Fonte , Bohner Marc
Published: October 2011

Phase-pure α-TCP powder was milled using a high-energy planetary mill to obtain a partially X-ray amorphous material. Calcination at temperatures between 350 and 600 °C was employed to recrystallize the powder. The phase composition as a function of calcination time and temperature was determined in-situ using high-temperature XRD equipment. It was found that the amorphous fraction recrystallized mainly to α-TCP, with only small amounts of β-TCP formed. At low temperatures (≤ 450 °C), a stable composition with approximately 85 wt-% α-TCP was found once 100% crystallinity was reached. The time required to reach full crystallinity depended on the calcination temperature. For temperatures > 450 °C a slow transformation to β-TCP was observed. The transformation rate depended on the calcination temperature and on the milling intensity. A moderately milled powder recrystallized to α-TCP, followed by a slow transformation to β-TCP at 600 °C, whereas an intensely milled powder also recrystallized to α-TCP, followed by a fast transformation to β-TCP at the same temperature.
Effect of Carbonate-Apatite on Bone Repair in Non-Critical Size Defect of Rat Calvaria
Authors: Valiense H. , Fernandes G.V.O. , Moura B. , Calasans-Maia J. , Alves A. , Rossi Antonella M. , Granjeiro J.M. , Calasans-Maia M.
Published: October 2011

The objective of this study was to investigate the bone repair of carbonate apatite (cHA) in comparison to hydroxyapatite (HA, control group), on osseous repair of non-critical size defect in rat calvaria. Spheres (400<ø>500μm) of both materials were synthesized under 37°C (cHA) and 90°C (HA) and were not sintered. Fifteen rats Wistar were submitted to general anesthesia and two perforations (4mm each) were made, one in each parietal bone, for implantation of cHA (left side) and HA spheres (right side). After 1, 3 and 6 weeks, five animals of each group were killed and the two fragments with the biomaterial were collected from the calvaria. The bone blocks with biomaterial were demineralized and 5μm thick semi-serial sections were done for histological analysis. The experimental group of 6 weeks did not show the presence of spheres of both biomaterials and few spheres were observed after 1 and 3 weeks. Histological analysis showed the connective tissue repairing the surgical defect after 1 week and newly formed bone after 3 weeks of surgery. Thus, we concluded both materials are biocompatible, promote osteoconduction and in all studied periods the biomaterials showed to be resorbable.
Study of the Release Potential of the Antibiotic Gentamicin from Microspheres of BCP
Authors: Osthues Rachel Mary , da Silva Sidney Nicodemos , Zavaglia Cecília A.C. , Fialho Sílvia Ligório
Published: October 2011

Orthopedics surgeries frequently are open surgeries, but the improvement of the specific instrumentation and the use of bioresorbable polymerics implants for regeneration of bone fractures are contributing to the development of noninvasive techniques such as an injectable bone substitute. These injectable materials are composites, formed by a particulate ceramic phase and a polymeric phase, and have the advantages of combining bioactivity and the ability to control degradation and some mechanical properties. In addition, microparticles present flexibility to fill several types of defects with closer packing and allow new bone growth and vascularization through the interconnected pores formed by the spaces between them. Another advantage of the particulate materials is that they have the potential to incorporate drugs such as antibiotics that can be applied in situ for treatment or prevention of bone infection, which is important because the poor circulation of blood in the osseous tissues makes necessary large amounts of these drugs to guarantee that an adequate dose reaches the affected site. This work evaluates the release potential of gentamicin from BCP spherical microparticles to be used in osseous injectable implants. The particles present a smooth geometry to prevent inflammatory reactions frequently caused by an irregular morphology, and their compositions offer a combination of biodegradability and stability. Microparticles with diameters between 150-425µm, were obtained by a method based on the immiscibility of liquids. To encapsulate the antibiotic, the spheres were immersed in a gentamicin solution, and after 24h they were separated and dried. The evaluation of the gentamicin release from the microspheres was carried out at 37°C in PBS, and the release medium was collected at predetermined time intervals for measurement of the amount released. This work demonstrates that these microspheres can find potential application in bone repair and regeneration.
The Effect of Pore Forming Agent Particle Size on the Porosity, Microstructure and In Vitro Studies of Hydroxyapatite Ceramics
Authors: Zalite V. , Locs Janis , Vempere D. , Berzina-Cimdina Liga
Published: October 2011

In situ viscous mass foaming with ammonium bicarbonate (NH4HCO3)as foaming agent was used for the preparation of porous hydroxyapatite ceramics. Three different particle fractions (100-300 μm, 300-500 μm, 500-1000 μm) of NH4HCO3 were used in order to evaluate the particle size effect on the ceramic microstructure. Foamed and dried green bodies were sintered at 1150°C. The porosity and microstructure of ceramics were determined with Archimedes method and scanning electron microscopy. As the NH4HCO3 particle fraction was decrease from 100-300 μm to 500-1000 μm, the open porosity increased from 42 to 54 %. In situ viscous mass foaming leads to the interconnected pore channels with wide pore size range (10-600 μm). In the present work cytotoxicity of obtained porous HA ceramics and fibroblast cell viability was investigated.
A New Natural Biomaterial: Sheep Dentine Derived Hydroxyapatite
Authors: Akyurt N. , Yetmez Mehmet , Karacayli U. , Gunduz O. , Agathopoulos Simeon , Gokce Hasan , Öveçoğlu M.L. , Oktar F.N.
Published: October 2011

Hydroxyapatite (HA) is a particularly attractive material for bone and tooth implants since it does not only closely resemble human tooth and bone mineral but it has also biologically proven to be compatible with these tissues. The applications of pure HA are restricted to non load bearing implants due to the poor mechanical properties of HA. Biomaterials of synthetic HA are highly reliable but the synthesis of HA is often complicate and expensive. Bioceramics of naturally derived biological apatites are more economic. Aim of the present work is to introduce sheep teeth dentine HA material as an alternative source of bioactive biomaterials for grafting purposes. The work was started with such a way that extracted sheep teeth were cleaned. The teeth were calcinated at 850°C in air. It was seen that enamel matter was easily separated from dentine after calcination. The collected dentine parts were crushed and ball milled. The powder was pressed between hardened steel dies to produce samples suitable for compression and microhardness tests. The obtained powder compacts were sintered at different temperatures, specifically 1000, 1100, 1200, and 1300°C in air. Results of microhardness and compression strength (along with the statistical analysis of these results) as well as those of SEM and XRD analyses are presented. In the literature, there is very little information about the mechanical properties of dentine and enamel matter derived from sheep, bovine and human. The highest compression strength value in the present study was measured around 146 MPa (from human dentine derived HA the highest value was almost 60 MPa after sintering at 1300°C). The best microhardness in the present study was found as nearly 125 HV. The results of this study showed that the HA material produced from sheep tooth dentine can be qualified as a promising source of HA needed to produce bioactive ceramics.
Nanostructures of Hydroxyapatite in Pluronic F 127: Preparation and Structural Characterization
Authors: de Oliveira Fortes Vanessa Danielle , Diniz Wandeberg Aranha , Araujo dos Santos Euler , Resende Cristiane Xavier , Almeida Luiz Eduardo , Teixeira Zaine
Published: October 2011

In this work, nanocomposites of hydroxyapatite and Pluronic F127 were prepared by a wet chemical method, using acid-basic reaction with Ca/P ratio of 1.67 in 10% (m/V) Pluronic F127 at 0, 37 and 90°C. The final concentration of Pluronic F127 was adjusted to 37% (m/V) at 4°C. Afterwards, the samples were lyophilized. Characterization was performed in purified samples (after Pluronic F127 removal), samples with 10% (m/V) of Pluronic F127 and calcined samples at 1000°C by X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Analyses by XRD of non-calcined samples showed that hydroxyapatite was obtained, in which the samples prepared at 0°C exhibited larger peaks attributed to lower crystallite sizes. For the calcined samples, both Raman spectroscopy and XRD exhibited hydroxyapatite for the syntheses at 37 and 90°C whereas the one prepared 90°C were identified as β-tricalcium phosphate (β-TCP). Morphological analysis by SEM indicated that the hydroxyapatite was sphere or rod agglomerates in mesoporous morphology for the nanocomposites prepared at 0 and 37°C, while the sample prepared at 90°C was nanospheres agglomerated into a smother matrix. After Pluronic F127 removal, samples fabricated at 0 and 37 °C exhibited coalescence of the nanostructures, whereas the sample synthesized at 90°C kept mesoporous. Calcined samples showed sintering and some rods structures.
Methodological Implications on Quantitative Studies of Cytocompatibility in Direct Contact with Bioceramic Surfaces
Authors: Cortês J.A. , Mavropoulos Elena , Hausen Moema , Rossi Alexandre , Granjeiro J.M. , Alves Gutemberg
Published: October 2011

Cell adhesion, proliferation and differentiation are important specific parameters to be evaluated on biocompatibility studies of candidate biomaterials for clinical applications. Several different methodologies have been employed to study, both qualitative and quantitatively, the direct interactions of ceramic materials with cultured mammal and human cells. However, while quantitatively evaluating cell density, viability and metabolic responses to test materials, several methodological challenges may arise, either by impairing the use of some widely applied techniques, or by generating false or conflicting results. In this work, we tested the inherent interference of different representative calcium phosphate ceramic surfaces (stoichiometric dense and porous hydroxyapatite (HA) and cation-substituted apatite tablets) on different tests for quantitative evaluation of osteoblast adhesion and metabolism, either based on direct cell counting after trypsinization, colorimetric assays (XTT, Neutral Red and Crystal Violet) and fluorescence microscopy. Cell adhesion estimation after trypsinization was highly dependent on the time of treatment, and the group with the highest level of estimated adhesion was inverted from 5 to 20 minutes of exposition to trypsin. Both dense and porous HA samples presented high levels of background adsorption of the Crystal Violet dye, impairing cell detection. HA surfaces also were able to adsorb high levels of fluorescent dyes (DAPI and phalloidin-TRITC), generating backgrounds which, in the case of porous HA, impaired cell detection and counting by image processing software (Image Pro Plus 6.0). We conclude that the choice for the most suitable method for cell detection and estimation is highly dependent on very specific characteristics of the studied material, and methodological adaptations on well established protocols must always be carefully taken on consideration.
Surface and Cell Affinity Properties of Chitosan-Gelatin-Hydroxyapatite Composite Films
Authors: Isikli C. , Hasirci N.
Published: October 2011

Addition of hydroxyapatite (HAp) into polymeric matrices and use them as supporting material for tissue engineering has gained attraction since hydroxyapatite (HAp) type crystals are the main inorganic components of the bone structure. In this study, composite films were prepared from chitosan (C) and gelatin (G) with addition of HAp, and the surface characterization and cell affinity properties were examined. The hydrophilicities and morphologies of the films were investigated by contact angle measurements and by scanning electron microscopy (SEM), respectively. Cell affinities were studied by using human osteosarcoma (SaOs-2) cell line. Crosslinked and HAp containing films were found to be more hydrophilic than that of the others, while surface free energy (SFE) values were almost similar for all films. Cell proliferation and spreading of SaOs-2 cells were higher for the films with high gelatin content and no HAp; whereas for HAp containing composites higher cell affinities were obtained for the samples which have high chitosan content.
Antibiotic Delivery Effects from HA on Bone Cement in the Interface Bioactive Bone Cement for Prevention of Infection in Joint Replacement
Authors: Oonishi Jr. Hiroyuki , Arita Tomonori , Tachibana Akira , Tanabe Toshizumi , Mizokawa Shigekazu , Oonishi Hironobu
Published: October 2011

Antibiotics release impregnated in HA granules, which were used in IBBC to prevent infection after total joint arthroplasty, was measured. For antibiotics, Flumarin, Vancomycin, Pansporin and Firstcin were used. Two models of antibiotics release were assumed; Model [I]: antibiotics release from surroundings of HA granules immediately after surgery and Model [II]: antibiotics release loaded on HA after antibiotics release from surroundings of HA granules as follows; (1) loading in normal pressure and (2) loading in reduced pressure. The amount of antibiotics loaded on HA is higher when loading is conducted under reduced pressure than that under normal pressure. Firstcin showed the highest loaded amount and the most desirable sustained release pattern. The antibiotics release from HA are varid depending on the antibiotics used.
29 to 24 Year-Clinical Results of Total Hip Arthroplasty Cemented with HA by Interface Bioactive Bone Cement (IBBC)
Authors: Oonishi Hironobu , Oonishi Jr. Hiroyuki , Mizokawa Shigekazu , Ohashi Hirotsugu , Ueno Masaru , Iwamoto Mikio
Published: October 2011

To improve the fixation of bone and bone cement in THA we used Interface Bioactive Bone Cement technique (IBBC) since 1982. For prostheses 28 mm-alumina head with polyethylene socket (Kyocera Co.) were used. In IBBC not-resorbable pure crystalline HA granules (0.3– 0.5 mm) were smeared on the bone surface in one to three layers just before packing bone cement. Group 1: IBBC was used in six joints in 1982. Group 2: In 25 patients, conventional bone cement technique (non-IBBC) in the one hip (in 1985 to 1986) and IBBC technique in the other hip (in 1986) were performed in the same patients. Group 3: In 65 patients (71 joints) IBBC were performed. Neither radiolucent line nor osteolysis appeared in all case in group 1. In group 2 in Non-IBBC the appearance rate of radiolucent line and osteolysis were rather high, however in IBBC they were extremely low. In Non-IBBC loosening were seen in 5 joints in the acetabulum and in 2 joints in the femur. However, in IBBC there was no loosening. In group 3 the radiolucent line and the osteolysis appeared extremely low. There was no loosening. In Non-IBBC the appearance rate of radiolucent line and the osteolysis was very high and the rate of loosening was 20%. However, in IBBC, radiolucent line and osteolysis will be prevented eternally.
Evaluation of Cytocompatibility of Bioglass-Niobium Granules with Human Primary Osteoblasts: A Multiparametric Approach
Authors: Fernandes G.V.O. , Alves Gutemberg , Linhares A.B.R. , Prado da Silva Marcelo Henrique , Granjeiro J.M.
Published: October 2011

The pursuit for an ideal bone substitute remains the main focus of many tissue engineering researchers. Among the myriad types of grafts available, synthetic bone grafts are of special importance, because it is available in large amounts, reduce the surgical trauma and eliminate the risk of diseases’ transmission. In this context, bioactive glasses have received attention mostly due to its described biocompatibility and rapid rate of surface reactivity when compared with other materials, allowing for faster interactions with the local tissue. The addition of niobium to this material has been shown as increasing the chemical resistance of the compound and providing greater stability. However, alterations on the chemical composition of biomaterials may impact on its biocompatibility. Therefore, the aim of this study was to evaluate the in vitro biocompatibility of bioglass-Niobium (BgNb) granules, in comparison with standard commercial bioglass (Biogran®) throughout an interesting multiparametrical approach, employing Phenol 2% and dense polystyrene beads as positive and negative controls, respectively. Extracts from each material were prepared by 24 hours incubation in culture medium (DMEM). Human primary osteoblasts were then exposed for 24 hours to each extract and cell viability was evaluated by three parameters: mitochondrial activity (XTT method), membrane integrity (neutral red dye uptake) and cell density (crystal violet dye exclusion test). BgNb extracts were highly compatible, since the levels of viable cells were similar to the control group (unexposed cells), on all parameters studied. The mean cell density on the Biogran® group was slightly lower than BgNb, even though this material was also non-cytotoxic. The excellent in vitro response for BgNb granules indicates the suitability of this material to future studies on its biological and physical properties when applied in vivo.
Improving the Bioactivity and Biocompatibility of Acrylic Cements by Collagen Coating
Authors: Cavalu Simona , Simon Viorica , Akin Ipek , Göller G.
Published: October 2011

Polymer-ceramic composites based on polymethyl methacrylate are widely used in orthopaedics as suture materials and fixation devices due to their biocompatibility and ability to support bony growth (osteoconductive) and also bone bioactive (to form a calcium phosphate layer on its surface). The aim of this study is to compare the microstructure, bioactivity and biocompatibility of new acrylic cement containing silver and collagen coated, with a comercial one, by in vitro study in simulated body fluid. In order to evaluate the properties of the surface layer, SEM microscopy and ATR-FTIR spectroscopy are used. The results indicates that both silver content and the presence of collagen layer favourise the mineralisation process at the surface.