Search results

The biomaterials are natural or synthetic materials used to improve quality of life either by replacing tissue/organ or assisting their function in medical field. The purpose of the study is to analyze the hydroxyapatite (HAP), HAP-TiO₂ (25 percent) composite coatings deposited on 316 LSS by High Velocity Flame Spray (HVFS) technique.

The coatings exhibit almost uniform and dense microstructure with porosity (HAP = 0.153 and HAP-TiO₂ composite = 0.138). Electrochemical corrosion testing was done on the uncoated and coated specimens in Ringer solution (SBF). As-sprayed coatings were characterized by XRD, SEM/EDS and cross-sectional X-ray mapping techniques before and after dipping in Ringer solution. Microhardness of composite coating (568.8 MPa) was found to be higher than HAP coating (353 MPa).

During investigations, it was observed that the corrosion resistance of steel was found to have increased after the deposition of HAP and HAP-TiO₂ composite coatings. Thus, coatings serve as an effective diffusion barrier to prohibit the diffusion of ions from the SBF into the substrate. Composite coatings have been found to be more corrosion resistant as compared to HAP coating in the simulated body fluid.

It has been concluded that corrosion resistance of HAP as well as composite coating is because of the desirable microstructural changes such as low porosity high microhardness and flat splat structures in coatings as compared to bare specimen.

This study is useful in the selection of biomedical implants.

This study is useful in the field of biomaterials.

No reported literature on corrosion behavior of HAP+ 25%- TiO₂ has been noted till now using flame spray technique. The main focus of the study is to investigate the HAP as well as composite coatings for biomedical applications.

Man has been seeking an ideal existence for a very long time. In this existence, justice, love, and peace are no longer words, but actual experiences. How ever, with the American preemptive invasion and occupation of Afghanistan and Iraq and the subsequent prisoner abuse, such an existence seems to be farther and farther away from reality. The purpose of this work is to stop this dangerous trend by promoting justice, love, and peace through a change of the paradigm that is inconsistent with justice, love, and peace. The strong paradigm that created the strong nation like the U.S. and the strong man like George W. Bush have been the culprit, rather than the contributor, of the above three universal ideals. Thus, rather than justice, love, and peace, the strong paradigm resulted in in justice, hatred, and violence. In order to remove these three and related evils, what the world needs in the beginning of the third millenium is the weak paradigm. Through the acceptance of the latter paradigm, the golden mean or middle paradigm can be formulated, which is a synergy of the weak and the strong paradigm. In order to understand properly the meaning of these paradigms, however, some digression appears necessary.

The purpose of this paper is to improve the generation efficiency of singlet oxygen of methylene blue molecules through finely controlling their aggregation states in drug carriers.

As a photosensitiser in photodynamic therapy, methylene blue (MB) was loaded on citrate-modified hydroxyapatite (HAp) through an electrostatic interaction and followed by encapsulation of coordination complexes of tannic acid (TA) and Fe(III) ions. Ultraviolet-visible absorption spectrum of the supernatant after incubation of samples was recorded at certain time interval to investigate the release behaviour of MB. Photodynamic activity of MB was determined by the oxidation reaction of uric acid by singlet oxygen generated by MB under illumination.

Almost all MB molecules were immediately released from HAp-MB, whilst an initial burst release of MB from HAp-MB@TA was followed by a sustainable and pH-sensitised release. In comparison with HAp-MB, photocatalystic reduction of HAp-MB@TA by titanium dioxide hardly occurred under illumination, indicating the stability against reduction to leukomethylene blue in vitro. Generation efficiency of singlet oxygen by MB released from HAp-MB@TA was significantly higher than that from HAp-MB because of the control of TA and Fe(III) ions complexes on molecular structures of released MB.

A facile method was herein demonstrated to optimise the generation efficiency of singlet oxygen by controlling aggregation states of PS molecules and improve PDT efficiency to damage tumour tissues.

Rapid prototyping (RP) technology is widely used in many fields in recent years. Bone tissue engineering (TE) is an interdisciplinary field involving life sciences, engineering and materials science. Hydroxyapatite (HAp) are similar to natural bone and it has been extensively studied due to its excellent biocompatibility and osteoconductivity. This paper aims to review nanoscaled HAp-based scaffolds with high porosity fabricated by various RP methods for bone regeneration.

The review focused on the fabrication methods of HAp composite scaffolds through RP techniques. The paper summarized the evaluation of these scaffolds on the basis of their biocompatibility and biodegradability through in vitro and in vivo tests. Finally, a summary and perspectives on this active area of research are provided.

HAp composite scaffold fabricated by RP methods has been widely used in bone TE and it has been deeply studied by researchers during the past two decades. However, its brittleness and difficulty in processing have largely limited its wide application in TE. Therefore, the formability of HAp combined with biocompatible organic materials and fabrication techniques could be effectively enhanced, and it can be used in bone TE applications finally.

This review paper presented a comprehensive study of the various types of HAp composite scaffold fabricated by RP technologies and introduced their potential application in bone TE, as well as future roadmap and perspective.

Man has been seeking an ideal existence for a very long time. In this existence, justice, love, and peace are no longer words, but actual experiences. How ever, with the American preemptive invasion and occupation of Afghanistan and Iraq and the subsequent prisoner abuse, such an existence seems to be farther and farther away from reality. The purpose of this work is to stop this dangerous trend by promoting justice, love, and peace through a change of the paradigm that is inconsistent with justice, love, and peace. The strong paradigm that created the strong nation like the U.S. and the strong man like George W. Bush have been the culprit, rather than the contributor, of the above three universal ideals. Thus, rather than justice, love, and peace, the strong paradigm resulted in in justice, hatred, and violence. In order to remove these three and related evils, what the world needs in the beginning of the third millenium is the weak paradigm. Through the acceptance of the latter paradigm, the golden mean or middle paradigm can be formulated, which is a synergy of the weak and the strong paradigm. In order to understand properly the meaning of these paradigms, however, some digression appears necessary.

Significant reduction in the emissions of organic hazardous air pollutants (HAP) associated with surface coating operations was demonstrated through the application of an innovative and low cost biofiltration system. A laboratory‐scale biofilter employing yard waste compost filter media was successful in reducing the methyl ethyl ketone (MEK) airborne concentrations to levels that consistently exceeded the regulatory performance standards mandated for surface coating air emissions control technologies. During Phase I, the biofilter reduced the influent airborne MEK concentration from 184ppmv (parts per million – volume basis) to zero, an operational performance that corresponded to a HAP removal rate of 1,084.2g/m³−d. Similarly, in Phase II, when the steady state influent airborne MEK concentration was increased to 608ppmv, the biofilter maintained an average effluent MEK concentration of 26.1ppmv, which reflected a HAP removal rate of 3,429.1g/m³−d or a 95.7 percent control efficiency.

This work concerns the electrodeposition of highly pure brushite (CaHPO₄·2H₂O) on titanium alloy substrates and the transformation of the brushite to hydroxyapatite (HAp) Ca₁₀(PO₄)₆(OH)₂ as a coating for orthopaedic implants. Thus, the electrodeposition of electrolyte containing calcium nitrate and ammonium hydrogen phosphate was carried out. The influences of the substrate surface treatment, the electroplating conditions (bath composition, current density, pH value and temperature) and the hydrothermal post treatment conditions on the deposition rate, the throwing power, the adhesion, the morphology and the structure of the coating were evaluated. High adhesion bond strength (around 23 mPa) was achieved on a rough clean substrate, which is slightly higher than plasma sprayed HAp coating on titanium alloy.

The purpose of this study was to investigate the influence of doping ions Mg²⁺, Zn²⁺, Al³⁺ to the structure of hydroxyapatite (HAP; Ca₁₀(PO₄)₆(OH)₂) and subsequently to evaluate their adaptation in structure and their anticorrosive properties.

The substituted hydroxyapatite was synthesized by precipitation method that included the addition of Mg²+, Zn²⁺ and Al³⁺ containing precursors to partially replace Ca²⁺ ions in the hydroxyapatite structure. For precipitation synthesis, three ratios of Ca/P = 1; 1.67; 3 and two values of pH = 7 and 12 were selected. Samples 1 (Ca/P = 1; pH = 7), 2 (Ca/P = 1.67; pH = 7), 3 (Ca/P = 3; pH = 7) and 5 (Ca/P = 1.67; pH = 12) were chosen to monitor the influence of doping ions Mg²⁺, Zn²⁺ and Al³⁺ to the structure of hydroxyapatite and its anticorrosive properties.

The chosen synthesis conditions are appropriate for the formation of crystalline HAP substituted by elements Mg, Zn and Al. Only for one sample (1-Mg), two different phases (hydroxyapatite and whitlockite) were identified in the phase composition. On the basis of preliminary corrosion tests, pigments were divided into three groups pursuant to their anticorrosion effectivity: pigments with high corrosion-inhibition efficiency; pigments without anticorrosive properties; and pigments that promote corrosion processes.

In addition, no doping effect can be observed except for the sample 1-Mg, which consists of two phases (hydroxyapatite and whitlockite). Preliminary corrosion tests prove that some samples of HAP have extremely high anticorrosive effectivity as effectivity of the commercial pigments. The accelerated corrosion test showed that HAP samples have insufficient corrosion-inhibition properties for coating applications compared with the commercial pigment.

This paper aims to investigate the vital characteristic of an innovative ceramic injection molding (CIM) process for orthopedic application with controlled porosity and improved tribological and mechanical properties which were affected by complex tribological interactions, whether lubricated like hip implants and other artificial prostheses. The main objective is to maximize the usage of palm stearin as a single based binder as the function of flow properties during injection molding process.

The binder used in this present study consists of 100 per cent palm stearin manufactured by Kempas Oil Sdn Bhd and supplied by Vistec Technology Sdn Bhd. The feedstock was prepared by using a Z-blade mixer (Thermo Haake Rheomix OS) and Brabender mixer model R2400. The feedstock prepared was injection molded using a manually operated vertical benchtop machine with an average pressure of about 5-7 bars. The firing step included the temporary holds at intermediate temperatures to burn out organic binders. At this stage, the green molded specimen was de-bound using a single-step wick-debinding method.

The maximum content of ceramic material is applied to investigate the efficiencies of net formulation that can be achieved by ceramic materials. The longer the viscosity will change with shear rate, the higher the value of n obtained instead. From the slope of the curves obtained in Figure 3, the value of n for the feedstock was determined to be less than 1, which indicates a pseudoplastic behavior and suitability for the molding process. Moreover, high shear sensitivity is important in producing complex and intrinsic specimens which are leading products in the CIM industry.

The feedstock containing HAp powder and palm stearin binder was successfully prepared at very low temperature of 70°C, which promoting a required pseudo-plastic behavior during rheological test. The single binder palm stearin should be optimized in other research works carried out, as palm stearin is most preferred compared to other polymeric materials that provided high energy consumption when subjected to the sintering process. Besides the binder is widely available in Malaysia, low cost and harmless effect during debinding process.

Job characteristics can potentially influence employees’ attitudes and behaviors. However, their impact on employees’ innovative behaviors, particularly in public sector organizations, has received little scholarly attention. Based on relational job design theory and the broaden-and-build theory of positive emotions, this study aims to examine the effect of job contact on public sector employees’ innovative work behavior through the mediator of happiness at work. It also assesses whether prosocial motivation strengthens the influence of job contact on innovative work behavior (via happiness at work).

The model was examined on a sample of 180 employee-supervisor dyads (90 supervisors and 180 employees) recruited from various government departments in the United Arab Emirates.

The findings support the proposed moderated mediation model in which job contact positively and significantly impacts innovative work behavior. The association between job contact and innovative behavior via happiness at work is found to be stronger for employees who are highly prosocially motivated.

The findings offer prescriptive insights into public sector employee happiness and prosocial motivation by illustrating when and how job contact influences innovative work behavior. The authors also present relevant managerial recommendations for promoting public sector employees’ innovative behavior.