Dissolution behavior of plasma-sprayed hydroxyapatite coatings.

Wollastonite coatings were deposited on Ti6Al4V substrate at the substrate temperatures of room temperature, 200 °C, 400 °C and 600 °C by the atmosphere plasma spraying, respectively. The effect of substrate temperature on the microstructure, phase composition, mechanical properties and dissolution behavior of wollastonite coatings were investigated. The microstructure and phase composition of coatings were examined by SEM and XRD. The hardness and elastic modulus were obtained by the Knoop indentation tests. In addition, the dissolution behavior of coatings was evaluated by immersion in SBF solution. The results indicate that a slight decrement of porosity and an obvious increment of crystallinity were found with the substrate temperature. The hardness and elastic modulus of coatings increased with the substrate temperature up to 400 °C firstly, and then a decrement was observed with the temperature further increasing to 600 °C. The dissolution rate of coatings characterized by the pH changes and the released Ca, Si and P concentration in the SBF decrease with the substrate temperature, which is related to the porosity and crystallinity of coatings. It is revealed that through increasing the substrate temperature during plasma spraying is a feasible method to improve the mechanical properties and to decrease the dissolution of wollastonite coatings.

When evaluating new bioactive glass compositions for their suitability as a biomaterial, one of the first steps is the study of their behavior in contact with aqueous solutions. Ion release, pH changes, and apatite precipitation are investigated during immersion experiments, and a wide variety of solutions is used, including simulated body fluid, Tris buffer solution, various cell culture medium formulations or deionized water. This paper reviews the different parameters used for immersion experiments on bioactive glasses. Results show that, depending on solution composition, pH, and buffering capacity, the experimental outcome is likely to vary. In addition, bioactive glass particle size and solution volume/glass surface area ratio affect the resulting ion concentration in solution, and, thus, the rate at which apatite is formed. It is, therefore, important to consider these effects when planning experiments, interpreting results or comparing the results of experiments performed in different laboratories.

The release of potassium, magnesium, and phosphate ions from aleurone cells of barley (Hordeum vulgare L. cv. Himalaya) is a gibberellic acid-dependent process. The release of these ions is preceded by a lag period of 6 to 8 hours after gibberellic acid addition. The effect of gibberellic acid on the release of ions is not mediated through an effect on ion solubilization. Thus, gibberellic acid does not apreciably affect the sum of extracted and released ions relative to controls. Rather, the effect of the hormone is on the release process itself. Inhibitors of oxidative phosphorylation when added with gibberellic acid or at times up to 6 hours after gibberellic acid inhibition release. When these inhibitors are added after ion release has begun, however, rapid efflux of ions occurs. These results suggest a strong correlation between energy levels and ion transport capacity. Inhibitors of RNA and protein synthesis also inhibit gibberellic acid-stimulated ion release. Evidence suggests that RNA and protein synthesis are required to establish and maintain ion release capacity of aleurone cells.

Assessment techniques for measurement of target erosion/ redeposition in large tokamaks

The heavy ion time‐of‐flight elastic recoil detection analysis (HI‐ERDA) technique was used to investigate the possibility of measuring near‐surface elemental depth profiles of light and mid‐ Z elements in thin films of plasma‐assisted molecular beam epitaxy (PAMBE)‐grown GaN and helium‐implanted titanium. The great advantage of HI‐ERDA is the ability to measure mass‐separated elemental depth profiles simultaneously. However for some materials it is not certain whether HI‐ERDA can be used successfully because significant sputtering or other beam‐induced damage may occur. The damage to the surfaces by a 77 MeV iodine beam was assessed using RBS, AFM and profilometry. The results show that for thin PAMBE‐grown polycrystalline GaN films and for titanium that has been heavily implanted with helium a significant modification of the near‐surface region is caused by the probing heavy ion beam. For the PAMBE‐grown GaN films the most significant loss trend is observed for nitrogen. Surprisingly this was not accompanied by a change in surface topology. In contrast, an almost complete removal of the heavily helium‐implanted surface layer was measured for the titanium specimens. The investigation shows that reference measurements with additional techniques such as RBS, AFM and profilometry have to be performed to ascertain sample integrity before HI‐ERDA data can be used. Copyright © 2004 John Wiley & Sons, Ltd.

Surface modification by substitution: Changing topology of conformational potential energy surfaces

The paper is dedicated to studying of the efficiency of application of the dust control agents not only for their original aims, but also for increasing of oxidation resistance of the solid fossil fuels. The complex investigation included: studying of coals quality alteration after treatment by the selected solution, scanning electron microscopy for investigation of their surface topology changes and, finally, ozonating treatment at low ozone concentrations with kinetic modeling for evaluation of oxidation resistivity. As it was expected, application of the selected solution allows no quality loss for coals. Scanning electron microscopy allowed to visualize the mechanism of working of the dust control agent. It revealed that the studied solution forms a thin smooth film around coal particles. This film tightly binds all the fine particles that were already formed and stored at the coal surface. Also, the solution tends to cover the surface thus decreasing the accessibility of the surface to active oxygen. The latter was proved by treated and untreated coals ozonating processing at low concentrations of ozone. The applied kinetic model allowed evaluation of the total coals activity to ozone decomposition. It was found that the treated coals have twice as low total activity to ozone decomposition as compared with the untreated ones. The latter parameter is closely related to coals oxidation resistivity (the lower the coals activity, the higher the coals oxidation resistivity). Therefore, it was finally concluded that application of the studied dust control agent allows for significant increase of sought-for quality indicator.

A descriptive model of wear evolution in rolling bearings

Properties of sodium- and potassium-activated adenosine triphosphatases of rat brain—effect of cyclopropane and other agents modifying enzyme activity

To assess- the release of calcium and phosphate ions from a fissure sealant containing amorphous calcium phosphate (ACP), and to determine the re-release capacity of these ions when charged with a solution containing casein phosphopeptide-amorphous calcium phosphate (CPP-ACP). Nine blocks of ACP resin-based sealant were prepared and immersed in three solutions at different pH (4.0, 5.5, 7.0), and calcium and phosphate ion release was measured with ion chromatography at 1, 3, 5, 7, 14, 21 and 28 days after immersion. Sixty days after immersion, each block was charged with CPP-ACP solution in three 7-day cycles to investigate the re-release of these ions, which was measured on days 1, 3, and 7. No difference was observed in initial calcium ion release at pH 4.0 and pH 5.5. At both values, ion release was significantly higher than at pH 7.0 (p<0.001). Initial phosphate release was significantly different among the three pH values (p<0.001). After re-charging the specimens, calcium ion re-release was greater than phosphate ion release. Initial ion release from ACP resin-based sealant was greatest at the lowest pH. Ion release decreased with time. As the number of recharge cycles increased, ion re-release also improved. Phosphate ion re-release required more recharge cycles than calcium ion re-release.

Objective: The aim of this study is to analyze the amount of calcium and phosphate ion released by casein phosphopeptide-amorphous calcium phosphate (CPP-ACP), which supports the remineralization and the effectiveness of propolis wax in suppressing the mass formation of Streptococcus mutans biofilm on caries-free subjects and to observe if these two active components are effective when combined into one substance and placed inside sugar-free chewing gum.Methods: Twenty-five samples of caries-free saliva before and after the mastication simulation (five concentrations of chewing gum) in vitro were observed to check for release of calcium and phosphate ions along with a biofilm assay. The release of calcium ions was detected using AAS, the release of phosphate ions was detected using spectrophotometry ultraviolet-visible, and the biofilm assay was detected using a crystal violet 96-well plate ELISA and was evaluated with an ELISA reader.Result: Chewing gum with a concentration of 0% prop + 5% CPP-ACP showed the highest release level of calcium ions (p&lt;0.05) and phosphate ions (p&gt;0.05) and is significant in suppressing the mass formation of the S. mutans biofilm (p&lt;0.05).Conclusions: Mastication simulation of CPP-ACP-Propolis chewing gum can increase calcium and phosphate ion levels in caries-free saliva and decrease S. mutans biofilm mass formation; this can support remineralization and becomes a dental caries prevention alternative.

The presence of heavy metals in the environment can be a serious problem because it is harmful to human health. One of the heavy metal ions that pollute the environment is the Cr6+ metal ion. The usual tool used to analyze metal ions is Cr6+ is the Atomic Absorption Spectrometry (AAS) and Inductively Couple Plasma (ICP) which are very expensive and require trained personnel. The purpose of this study was to design a simple detector for Cr6+ metal ions as an alternative to conventional methods using AAS and ICP. The detection tool was developed using the android-based digital image method with SLR data analysis techniques obtained from the reaction of the metal ion complex Cr6 + with the compound dhypenilcarbazida (DPC). The parameters of the tool measured were accuracy, selectivity and sensitivity with the reaction of DPC compounds as complexes. The comparison level of this method is the complex method with DPC using a UV-Vis spectrophotometer. This research was carried out in the Chemistry Laboratory FKIP UNIB in November 2018 until March 2019. The implementation of tool parameters was tested to samples of aquatic environments in Bengkulu City, namely PDAM Kota Bengkulu water, tap water of FKIP UNIB Dean, Lake UNIB water, Sungai Hitam water and water Pantai Panjang. The results showed that the detection of Cr6+ metal ions made by the android-based digital image method had better accuracy, selectivity and sensitivity than conventional methods. The DPC is selective for Cr6 + metal ions with a change in color from clear to violet, at a wavelength of 540 nm. Accuracy was checked using a UV-Vis spectrophotometer with 99% accurate results. After that, test sensitivity to Cr6 + metal ions. using the android application method generates a Limit of Detection (LOD) of 6.7 ppb. The detector that was developed was applied to water samples in the city of Bengkulu, it turned out that all of the water samples showed that the levels of Cr6+ metal ions were still below the threshold determined by the Minister of Health Regulation, so it was still safe to use in everyday life.

AimThis study evaluated the 12-month ion release, fluoride recharge capacity, pH modulation, mechanical aging, and structural reliability of an experimental amorphous calcium phosphate (ACP)-based composite compared to contemporary bioactive restorative materials.MethodsAn experimental ACP composite was compared with Activa™ BioACTIVE-Restorative, Cention N, and Surefil one ™. Calcium (Ca2+), phosphate (PO43−), and fluoride (F−) release, along with pH changes, were assessed over 365 days in artificial saliva. Fluoride recharge was performed at six months using a single application of 5000 ppm sodium fluoride gel, followed by cumulative fluoride re-release measurement for 30 days. The flexural strength and modulus were evaluated at baseline, 6 months, and 12 months. Statistical analysis was conducted using mixed-model ANOVA with post-hoc tests, and flexural strength reliability was assessed using Weibull analysis (α = 0.05).ResultsAll materials exhibited an initial burst of ion release, followed by a progressive decline (p = 0.001). The ACP composite demonstrated the highest early calcium and phosphate release but negligible fluoride release and significant reductions in mechanical properties and reliability after aging. Cention N showed sustained multi-ion release, the greatest alkalizing capacity, and stable mechanical performance. Surefil one™ achieved the highest fluoride release and recharge capacity while maintaining a near-neutral pH and superior mechanical reliability. The Activa™ BioACTIVE-Restorative exhibited moderate ion release and intermediate mechanical performance.ConclusionsBioactive restorative materials exhibit distinct material-dependent behaviors. Alkasite-based systems showed balanced ion release and mechanical stability, fluoride-focused systems demonstrated superior recharge and reliability, and the ACP composite provided primarily short-term calcium–phosphate release with limited long-term durability.

Release of zinc and phosphate ions from glasses has been studied in aqueous medium (pH—5.7, 6.5 and 8.0). Zinc phosphate glasses of five different compositions corresponding to ZnO: P2O5 molar rati...

In the global scenario, wind turbines and their aerodynamics are always subjected to constant research for increasing their efficiency which converts the abundant wind energy into usable electrical energy. In this research, an attempt is made to increase the efficiency through the changes in surface topology of wind turbines through computational fluid dynamics. Dimples on the other hand are very efficient in reducing air drag as is it evident from the reduction of drag and increase in lift in golf balls. The predominant factors influencing the efficiency of the wind turbines are lift and drag which are to be maximized and minimized respectively. In this research, surface of turbine blades are integrated with dimples of various sizes and arrangements and are analyzed using computational fluid dynamics to obtain an optimum combination. The analysis result shows that there is an increase in power with about 15% increase in efficiency. Hence, integration of dimples on the surface of wind turbine blades has helped in increasing the overall efficiency of the wind turbine.