The effect of perfusion culture on proliferation and differentiation of human mesenchymal stem cells on biocorrodible bone replacement material

Biocorrodible iron foams were coated with different calcium phosphate phases (CPP) to obtain a bioactive surface and controlled degradation. Further adhesion, proliferation and differentiation of SaOs-2 and human mesenchymal stem cells were investigated under both static and dynamic culture conditions. Hydroxyapatite (HA; [Ca₁₀(PO₄)₆OH₂]) coated foams released 500 μg/g iron per day for Dulbecco's modified eagle medium (DMEM) and 250 μg/g iron per day for McCoys, the unmodified reference 1000 μg/g iron per day for DMEM and 500 μg/g iron per day for McCoys, while no corrosion could be detected on brushite (CaHPO₄) coated foams. Using a perfusion culture system with conditions closer to the in vivo situation, cells proliferated and differentiated on iron foams coated with either brushite or HA while in static cell culture cells could proliferate only on Fe-brushite. We conclude that the degradation behaviour of biocorrodible iron foams can be varied by different calcium phosphate coatings, offering opportunities for design of novel bone implants. Further studies will focus on the influence of different modifications of iron foams on the expression of oxidative stress enzymes. Additional information about in vivo reactions and remodelling behaviour are expected from testing in implantation studies.     

Specific heat, electrical resistivity and thermoelectric power of YbNi4Si

The studies of the specific heat, electrical resistivity and thermoelectric power of YbNi₄Si are reported. These studies are supported by magnetic susceptibility and X-ray photoemission spectroscopy (XPS) measurements. YbNi₄Si does not order magnetically down to 4 K. Nearly in the whole temperature range studied the magnetic susceptibility follows a Curie law with μ_eff = 4.15 μ_B/f.u. This effective magnetic moment is close to the value expected for the 4f¹³ configuration (4.54 μ_B). The Yb²⁺ and Yb³⁺ peaks observed by XPS in the valence band region confirm the domination of the Yb³⁺ valence state. Based on the specific heat measurements, the electronic specific heat coefficient γ = 25 mJ/mol/K² and the Debye temperature θ_D = 320 K were derived. A quadratic dependence of electrical resistivity at low temperatures has been observed. The Kadowaki-Woods ratio has been discussed. The thermoelectric power has been analyzed in the framework of the two band model.     

Fatigue and cyclic creep of replicated microcellular aluminium

The cyclic behaviour of 400 μm pore size replicated aluminium foam is assessed in tension-tension fatigue with a stress ratio equal to 0.1, keeping the load amplitude constant, for relative density values comprised between 0.175 and 0.220. The number of cycles to failure ranges from 6 × 10² (lowest relative density) to 5 × 10⁶ (highest relative density). The foams display cyclic creep coupled with a strong influence of relative density on their general fatigue performance. Data analysis shows that the foam fatigue behaviour is dominated by cyclic creep, which governs both the deformation and the fatigue life of the cycled specimens, yielding characteristics globally in line with what is expected knowing the metal making the foam.     

Poly(D,L-lactide) (PDLLA) foams with TiO2 nanoparticles and PDLLA/TiO2-Bioglass® foam composites for tissue engineering scaffolds

Porous poly(D,L-lactide) PDLLA foams containing 0, 5 and 20 wt% of TiO₂ nanoparticles were fabricated and characterised. The addition of Bioglass^® particles was also studied in a composite containing 5 wt% of Bioglass^® particles and 20 wt% of TiO₂ nanoparticles. The microstructure of the four different foam types was characterised using scanning electron microscopy (SEM) and their mechanical properties assessed by quasi-static compression testing. The in vitro behaviour of the foams was studied in simulated body fluid (SBF) at three different time points: 3, 21 and 28 days. The degradation of the samples was characterised quantitatively by measuring the water absorption and weight loss as a function of immersion time in SBF. The bioactivity of the foams was characterised by observing hydroxyapatite (HA) formation after 21 days of immersion in SBF using SEM and confirmed with X-ray diffraction (XRD) analysis. It was found that the amount of HA was dependent on the distribution of TiO₂ nanoparticles and on the presence of Bioglass^® in the foam samples.     

Toxicity of mercury on in vitro development of parthenogenetic eggs of a freshwater cladoceran Daphnia carinata

Chronic toxicity test duration of 21 days for daphnid is time consuming and expensive. Therefore, the developmental stages of Daphnia carinata eggs that could be used as potential endpoints for sublethal and chronic toxicity tests have been investigated and defined. Daphnid egg test is simple, easy to conduct and handle in the laboratory, and cost-effective. The 72 h ‘egg arrest’ bioassay system could be an alternative to the classic 21-day chronic test with neonates of daphnid. The main aims of the study were to establish easy to identify stages of D. carinata egg that could be used as potential endpoints for toxicity tests with in vitro cultures of daphnid parthenogenetic eggs. Commonly available Indian freshwater cladoceran Daphnia carinata parthenogenetic eggs in vitro were exposed to water borne mercury concentrations, ranging from 0.1 to 32 μg l⁻¹. Adult female cladoceran D. carinata have eight main developmental stages of parthenogenetic reproduction based on the release of external and internal membranes, formation of cephalic and body regions, appearance of secondary antennae, presence of two pink eyes, than a single black eye, and finally caudal or shell spine separation and finally free-swimming neonate within 65–72 h. At 1, 3.2 and 10 μg l⁻¹ of Hg concentrations; the 25, 50 and 70% embryonic developmental arrests were observed. The lower concentrations of Hg (0.32, 1, and 3.2 μg l⁻¹) tested in the present study are not generally harmful to the neonates and adults daphnid species, but the same are highly toxic to the embryos of D. carinata. The 48 h and 72 h EC₅₀s and their 95% confidence limits for survival and hatchability were lower than previously reported 48 h EC₅₀s for Daphnia magna immobilization assay. The egg of D. carinata turned out to be a suitable alternative model for ecotoxicological and water quality assessment studies.     

Fabrication and characterization of novel hydroxyapatite/porous carbon composite scaffolds

Novel hydroxyapatite (HA)/porous carbon composite scaffolds were prepared by applying sonoelectrodeposition and a subsequent hydrothermal treatment to previous carbonized phenolic resin coated polyurethane sponges. The interconnected pore network and morphology of HA/porous carbon composite scaffolds were determined by scanning electron microscope (SEM), and the whole surface of porous carbons were evenly coated with the deposited HA layer which was confirmed by EDS and XRD. The porosity (83.5 ± 0.3%) and the bulk density (0.297 ± 0.009 g·cm⁻³) of HA/porous carbon scaffolds were detected by the Archimedes method. The compressive and flexural strength of the scaffolds is 1.187 ± 0.064 MPa and 0.607 ± 0.268 MPa, respectively. Compared with the polymeric surface of 24-well cell culture plates, these novel scaffolds significantly promote the proliferation of human osteoblast-like MG-63 cells, indicating that this novel HA/porous carbon composite scaffold could be used for in vitro 3D culture of osteoblasts.     

Improved dielectric and ferroelectric properties in Ti-doped BiFeO3-PbTiO3 thin films prepared by pulsed laser deposition

Ti-modified thin films of multiferroic 0.72Bi(Fe_1 − xTi_x)O₃-0.28PbTiO₃ (BFPT, x = 0 and 0.02) solid solution were prepared by pulsed laser deposition. The BFPT (x = 0 and 0.02) films possess a tetragonal structure with highly preferential (001) orientation. The effects of the ionic substitution on the properties of BFPT (x = 0 and 0.02) films have been investigated. The leakage current of the BFPT (x = 0.02) thin film is significantly reduced, and the dielectric and ferroelectric properties greatly improved by the aliovalent ionic substitution of Ti⁴⁺ for Fe³⁺. The BFPT (x = 0.02) thin film exhibits a reasonably high remnant polarization P_r with 2P_r up to 90 μC/cm² at 312 kV/cm and a switchable polarization up to 92 μC/cm² at 417 kV/cm.     

Effect of bio-sludge concentration on the efficiency of sequencing batch reactor (SBR) system to treat wastewater containing Pband Ni

The removal efficiency of sequencing batch reactor (SBR) system with synthetic industrial estate wastewater (SIEWW) containing Ni²⁺ or Pb²⁺ was increased with the increase of mixed liquor suspended solids (MLSS). But, the sludge volume index (SVI) of the system was increased up to higher than 100 mL/g under MLSS of up to 4000 mg/L. Also, the effluent NO₃⁻ was decreased with the increase of MLSS. The heavy metals (Ni²⁺ or Pb²⁺), BOD₅, COD and TKN removal efficiencies of SBR system with SIEWW containing 5 mg/L heavy metal (Ni²⁺ or Pb²⁺) under MLSS of 3000 mg/L were 83–85%, 96–97%, 95–96% and 83–94%, respectively. The increase of heavy metal (Ni²⁺ or Pb²⁺) concentrations of SIEWW from 5 to 50 mg/L were not significantly effected to both COD and BOD₅ removal efficiencies (they were reduced by only 4–5%), but they were strongly effected to both TKN and heavy metals removal efficiencies (they were reduced by 15 and 20–30%, respectively). Both Ni²⁺ and Pb²⁺ could repress the growth of both nitrification and denitrification bacteria. And Ni²⁺ was more effective than Pb²⁺ to reduce the heavy metals removal efficiency. The SBR system could be applied to treat the industrial estate wastewater (IEWW) containing both Pb²⁺ and Ni²⁺ even the heavy metals concentrations was up to 5 mg/L, but the removal efficiency was quite low and excess bio-sludge did not produce. However, the system efficiency could be increased with the increase of BOD₅ concentration of the wastewater. The Pb²⁺, Ni²⁺, COD, BOD₅ and TKN removal efficiencies of the system with IEWW containing 500 mg/L BOD₅, 5 mg/L Ni²⁺ and 5 mg/L Pb²⁺ under HRT of 3 days were 85.68 ± 0.31%, 87.03 ± 0.21%, 86.0 ± 0.5%, 94.04 ± 0.4% and 90.5 ± 0.9%, respectively. And the effluent SRT, SS and SVI of the system were 44.7 ± 0.6 days, 150 ± 6 mg/L and 100 mL/g, respectively.     

Influence of isovalent ion substitution on the electrochemical performance of LiCoPO4

LiCo_1−xM_xPO₄ (M = Mg²⁺, Mn²⁺ and Ni²⁺; 0 ≤ x ≤ 0.2) compounds have been synthesized by solid-state reaction method and studied as cathode materials for secondary lithium batteries. LiCoPO₄ exhibits a discharge plateau at ∼4.7 V with an initial discharge capacity of 125 mAh/g and on cycling capacity falls. Substitution of Co²⁺ with Mg²⁺/Mn²⁺/Ni²⁺ in LiCoPO₄ has an influence on the initial discharge capacity and on cycling behaviour. The capacity retention of LiCoPO₄ is improved by manganese substitution. Among the manganese substituted phases, LiCo_0.95Mn_0.05PO₄ shows good reversible capacity of ∼50 mAh/g.     

Novel modeling concept for evaluating the effects of cadmium and copper on heterotrophic growth and lysis rates in activated sludge process

A new modeling concept to evaluate the effects of cadmium and copper on heterotrophic growth rate constant (μ_H) and lysis rate constant (b_H) in activated sludge was introduced. The oxygen uptake rate (OUR) was employed to measure the constants. The results indicated that the μ_H value decreased from 4.52 to 3.26 d⁻¹ or by 28% when 0.7 mg L⁻¹ of cadmium was added. Contrarily the b_H value increased from 0.31 to 0.35 d⁻¹ or by 11%. When adding 0.7 mg L⁻¹ of copper, the μ_H value decreased to 2.80 d⁻¹ or by 38%. The b_H value increased to 0.42 d⁻¹ or by 35%. After regression, the inhibitory effect was in a good agreement with non-competitive inhibition kinetic. The inhibition coefficient values for cadmium and copper were 1.82 and 1.21 mg L⁻¹, respectively. The relation between the b_H values and heavy metal concentrations agreed with exponential type well. The heavy metal would enhance b_H value. Using these data, a new kinetic model was established and used to simulate the degree of inhibition. It was evident that not only the inhibitory effect on μ_H but also that the enhancement effect on b_H should be considered when heavy metal presented.     

Effect of metal ions on reactive dye decolorization by laccase from Ganoderma lucidum

In this work, the influence of different metal ions on laccase activity and laccase-catalyzed dye decolorization was investigated under in vitro conditions using crude laccase obtained from a white rot fungus Ganoderma lucidum. Laccase activity was enhanced by metal ions such as Ca²⁺, Co²⁺, Cu²⁺ and Zn²⁺ at low concentrations (1 mM). Increasing the concentration of metal ions except that of Cu²⁺ and Zn²⁺ up to 5 mM and above decreased the enzyme activity. Among several heavy metals, Fe²⁺ highly inhibited the enzyme activity. Effect of metal ions was tested on decolorization of two reactive dyes, namely Remazol black-B (RB-5) and Remazol brilliant blue R (RBBR) at a concentration of 50 mg l⁻¹. The presence of heavy metals generally did not exert much influence on the decolorization except Fe²⁺. Cu²⁺ and Cr⁶⁺ enhanced the decolorization of both dyes. In the presence of 1 mM Cu²⁺, 94% of RB-5 and 35.5% of RBBR were decolorized during 1 h incubation. G. lucidum laccase was able to tolerate mixture of several metal ions. Treatment of simulated reactive dye effluent by laccase showed that the redox mediator system is necessary for effluent decolorization. Syringaldehyde, a natural redox mediator, was very effective than the synthetic mediator 1-hydroxybenzotriazole (HBT). The initial rate of effluent decolorization in presence of syringaldehyde (0.0831 h⁻¹) was 5.6 times higher than HBT (0.0152 h⁻¹). Although the rate of decolorization was markedly decreased in the effluent containing mixed metal ions, presence of syringaldehyde showed effective decolorization. This study indicates that G. lucidum laccase and natural redox mediator system could be a potential candidate for color removal from reactive dye effluent.     

TiO2-coated foams as a medium for solar catalysis

Sunlight irradiating the surface of the Earth represents a maximum input available for a solar catalytic process of 50 W_UV m⁻². We propose using high-porosity, metallic, reticulated foams as the support medium for the photocatalyst in order to improve the apparent quantum yield. The layer of TiO₂ was applied by dip-coating. The measurement of the degradation kinetics was carried out on a model target molecule, 2,4 dichlorophenol, at an initial concentration of 10 mg l⁻¹. The aim was to assess the efficiency of the foams as a photocatalytic media compared to that of a suspension of catalytic powder (Degussa P25) and the flat 2D support (Ahlstrom cellulose media). The apparent quantum yield of the foam scaffold carrying the TiO₂ was high, showing that, as with the powder suspension, foam makes good use of the UV rays to break down molecules. It is noteworthy that the apparent quantum yield of the foam tended towards that observed for suspensions which form the ideal support thanks to their optimal ability to harness the light.     

Membrane optode for mercury(II) determination in aqueous samples

A color changeable optode for Hg(II) was prepared by the immobilization of a dye 4-(2-pyridylazo)resorcinol (PAR) and a liquid ion-exchanger trioctylmethylammonium chloride (Aliquat-336) in the tri-(2-ethylhexyl) phosphate plasticized cellulose triacetate matrix. Hg(II) and CH₃Hg⁺ from aqueous samples could be quantitatively preconcentrated in this transparent optode producing a distinct color change (λ_max = 520 nm) within 5 min equilibration time in bicarbonate aqueous medium or 30 min in natural water. Whereas optode sample without Aliquat-336 did not change its color corresponding to Hg–PAR complex on equilibrium with the same aqueous solution containing Hg(II) ions. The uptake of Hg(II) was found to be pH dependant with a maximum (>90%) at a pH 7.5. The uptake of ions like Cu(II), Fe(II), Zn(II) and Pb(II) was negligible in the optode where as the uptake of Cd(II) and Zn(II) ions was 10–15% at pH 7.5. The optode developed in the present work was studied for its analytical application for Hg(II) in the aqueous samples by spectrophotometry, radiotracer (²⁰³Hg), Energy Dispersive X-ray Fluorescence (EDXRF) analyses and Instrumental Neutron Activation Analysis (INAA). The minimum amount of Hg(II) required to produce detectable response by spectrophotometry, INAA and EDXRF were found to be 5.5, 1 and 12 μg, respectively. This optode showed a linear increase in the absorbance at λ_max = 520 nm over a concentration range of 0.22–1.32 μg/mL of Hg(II) ions in aqueous solution for 5 min. The preconcentration of Hg(II) from large volume of aqueous solution was used to extend the lower limit of concentration range that can be quantified by the spectrophotometry of optode. It was observed that preconcentration of 11 μg Hg(II) in 100 mL (0.11 μg/mL) in aqueous samples gives a distinct color change and absorbance above 3σ of the blank absorbance. The optode developed in the present work was found to be reusable.     

Enhanced multiferroic properties and tunable magnetic behavior in multiferroic BiFeO3-Bi0.5Na0.5TiO3 solid solutions

A series of multiferroic (1−x)BiFeO₃−x(Bi_0.5Na_0.5)TiO₃ (BF-BNT) (x = 0 − 0.6) solid solution ceramics were prepared by a sol-gel method. The XRD results show that increasing BNT content induce a gradual phase transformation from rhombohedral to pseudocubic structure near x = 0.4. Compared with pure BiFeO₃, superior multiferroic properties are obtained for x = 0.3 with remnant polarization P_r = 1.49 μC/cm² and saturated magnetization M_s = 0.51 emu/g. Importantly, the paramagnetic (PM) to ferromagnetic (FM) transition is observed for the solutions, and the Curie temperature (T_C) can be tuned by varying the content of BNT. This observed FM ordering is discussed in terms of the possible existence of the long-range superexchange interaction of Fe³⁺-O-Ti-O-Fe³⁺ in the chemically ordered regions.     

Polypropylene foam behaviour under dynamic loadings: Strain rate,density and microstructure effects

Expanded polypropylene foams (EPP) can be used to absorb shock energy. The performance of these foams has to be studied as a function of several parameters such as density, microstructure and also the strain rate imposed during dynamic loading. The compressive stress–strain behaviour of these foams has been investigated over a wide range of engineering strain rates from 0.01 to 1500 s⁻¹ in order to demonstrate the effects of foam density and strain rate on the initial collapse stress and the hardening modulus in the post-yield plateau region. A flywheel apparatus has been used for intermediate strain rates of about 200 s⁻¹ and higher strain rate compression tests were performed using a viscoelastic Split Hopkinson Pressure Bar apparatus (SHPB), with nylon bars, at strain rates around 1500 s⁻¹ EPP foams of various densities from 34 to 150 kg m⁻³ were considered and microstructural aspects were examined using two particular foams. Finally, in order to assess the contribution of the gas trapped in the closed cells of the foams, compression tests in a fluid chamber at quasi-static and dynamic loading velocities were performed.     

A novel ultra-light structure for radiation shielding

A new ultra-light structure based on the application of open-cell metal foams has been designed and investigated to determine its ability for attenuation of γ-rays and thermal neutrons. Open-cell metal foam, a unique class of material, has been employed in the structure and is studied in this work where radiation attenuation abilities of foams and foams filled with water and borated water have been compared with bulk Aluminum. The γ-ray attenuation measurements were performed using γ-ray at 0.662, 1.173 and 1.332 MeV photon energies and thermal neutron attenuation measurements were conducted using a polyenergetic thermal neutron beam. The results show that the metallic foam by itself attenuates less γ-ray as compared to bulk material, while the mass attenuation coefficients of foams filled with water is higher than that of bulk metals. The thermal neutron experiment, on the other hand, has shown a dramatic attenuation improvement in foams filled with water and particularly with borated water as compared to bulk metal and foam.     

Mechanical characterization of dense calcium phosphate bioceramics with interconnected porosity

Porous hydroxyapatite/tricalcium phosphate (HA/TCP) bioceramics were fabricated by a novel technique of vacuum impregnation of reticulated polymeric foams with ceramic slip. The samples had approximately 5–10% interconnected porosity and controlled pore sizes appropriate to allow bone ingrowth, combined with good mechanical properties. A range of polyurethane foams with 20, 30 and 45 pores per inch (ppi) were used as templates to produce samples for testing. The foams were inpregnated with solid loadings in the range of 60–140 wt%. The results indicated that the average apparent density of the HA/TCP samples was 2.48 g/cm³, the four-point bending strength averaged 16.98 MPa, the work of fracture averaged 15.46 J/m² and the average compressive strength was 105.56 MPa. A range of mechanical properties resulted from the various combinations of different grades of PU foam and the solid loading of slips. The results indicated that it is possible to manufacture open pore HA/TCP bioceramics, with compressive strengths comparable to human bone, which could be of significant clinical interest.     

Ag and O ion irradiation induced improvement in dielectric properties of the Ba(Co1/3Nb2/3)O3 thin films

We present the preliminary results of temperature and frequency dependent dielectric measurements on Ba(Co_1/3Nb_2/3)O₃ (BCN) thin films. These films were prepared on indium tin oxide (ITO) coated glass substrates by the pulse laser deposition (PLD) technique. It exhibits single-phase hexagonal symmetry. These films were irradiated with Ag¹⁵⁺ (200 MeV) and O⁷⁺ (100 MeV) beams at the fluence 1 × 10¹¹, 1 × 10¹², and 1 × 10¹³ ions/cm². On irradiating these films, its dielectric constant (?′) and dielectric loss (tan δ) parameters improve compared to un-irradiated film. Compared to O⁷⁺ irradiation induced point/cluster defects Ag¹⁵⁺ induced columnar defects are more effective in reducing/pinning trapped charges within grains. The present paper highlights the role of swift heavy ion irradiation in engineering the dielectric properties of conductive samples to enable them to be useful for microwave device applications.     

Investigation of a basic dye removal from aqueous solution onto chemically modified Unye bentonite

The adsorption behavior of crystal violet (CV⁺) from aqueous solution onto magnesium-oxide coated bentonite (MCB) sample was investigated as a function of parameters such as initial CV⁺ concentration, contact time and temperature. The Langmuir, and Freundlich adsorption models were applied to describe the equilibrium isotherms. The Langmuir monolayer adsorption capacity of MCB were estimated as 496 mg/g. The pseudo-first-order, pseudo-second-order kinetic and the intra-particle diffusion models were used to describe the kinetic data and rate constants were evaluated. The values of the energy (E_a), enthalpy (ΔH^≠) and entropy of activation (ΔS^≠) were 56.45 kJ/mol, 53.90 kJ/mol and −117.26 J/mol K, respectively, at pH 6.5.     

Synthesis of spherical nanostructured LiMxMn2−xO4 (M = Ni, Co, and Ti; 0 ≤ x ≤ 0.2) via a single-step ultrasonic spray pyrolysis method and their high rate charge-discharge performances

LiM_xMn_2−xO₄ (M = Ni²⁺, Co³⁺, and Ti⁴⁺; 0 ≤ x ≤ 0.2) spinels were prepared via a single-step ultrasonic spray pyrolysis method. Comparative studies on powder properties and high rate charge-discharge electrochemical performances (from 1 to 15 C) were performed. XRD identified that pure spinel phase was obtained and M was successfully substituted for Mn in spinel lattice. SEM and TEM studies confirmed that powders had a feature of ‘spherical nanostructural’, that is, powders consisted of spherical secondary particles with the size of about 1 μm, which were developed from close-packed primary particles with several tens of nanometers. Substitutions enhanced density of second particles to different extents, depending on M and its content. Charge-discharge tests showed that as-prepared LiMn₂O₄ could deliver excellent rate performance (around 100 mAh/g at 10 C). Ni substitution contributed to improving electrochemical performances. In the voltage range of 4.95-3.5 V, the materials showed much better electrochemical performances than LiMn₂O₄ in terms of capacity, cycleability and rate capability.