Necessity of dietary calcium supplement in file fish (Monacanthus cirrhifer)

File fish, Monacanthus cirrhifer, juveniles with initial mean body weight of 0.27g were fed purified diets with or without calcium (Ca) supplement for 10 weeks at a water temperature of 27.0±1.4°C. Growth was significantly low in fish fed diet without Ca supplement than fish fed diet with Ca supplement. Feed efficiency and condition of fish were also significantly decreased in absence of a dietary Ca supplementation, Minerals contents of bone were similar in both the treatment groups and did not appear as a suitable indicator of Ca requirement. It appeared that Ca supplement to the purified diet is necessary for file fish for their proper growth and feed utilization.

An investigation of the kinetics of CO2 uptake by a synthetic calcium based sorbent

This study examines the kinetics of carbonation by CO2 at temperatures of ca. 750 °C of a synthetic sorbent composed of 15 wt% mayenite (Ca12Al14O33) and CaO, designated HA-85-850, and draws comparisons with the carbonation of a calcined limestone. In-situ XRD has verified the inertness of mayenite, which neither interacts with the active CaO nor does it significantly alter the CaO carbonation–calcination equilibrium. An overlapping grain model was developed to predict the rate and extent of carbonation of HA-85-850 and limestone. In the model, the initial microstructure of the sorbent was defined by a discretised grain size distribution, assuming spherical grains. The initial input to the model – the size distribution of grains – was a fitted parameter, which was in good agreement with measurements made with mercury porosimetry and by the analysis of SEM images of sectioned particles. It was found that the randomly overlapping spherical grain assumption offered great simplicity to the model, despite its approximation to the actual porous structure within a particle. The model was able to predict the performance of the materials well and, particularly, was able to account for changes in rate and extent of reaction as the structure evolved after various numbers of cycles of calcination and carbonation.

An investigation of the kinetics of CO 2 uptake by a synthetic calcium based sorbent

This study examines the kinetics of carbonation by CO 2 at temperatures of ca. 750°C of a synthetic sorbent composed of 15wt% mayenite (Ca 12Al 14O 33) and CaO, designated HA-85-850, and draws comparisons with the carbonation of a calcined limestone. In-situ XRD has verified the inertness of mayenite, which neither interacts with the active CaO nor does it significantly alter the CaO carbonation-calcination equilibrium. An overlapping grain model was developed to predict the rate and extent of carbonation of HA-85-850 and limestone. In the model, the initial microstructure of the sorbent was defined by a discretised grain size distribution, assuming spherical grains. The initial input to the model - the size distribution of grains - was a fitted parameter, which was in good agreement with measurements made with mercury porosimetry and by the analysis of SEM images of sectioned particles. It was found that the randomly overlapping spherical grain assumption offered great simplicity to the model, despite its approximation to the actual porous structure within a particle. The model was able to predict the performance of the materials well and, particularly, was able to account for changes in rate and extent of reaction as the structure evolved after various numbers of cycles of calcination and carbonation. © 2011 Elsevier Ltd.

Size effects in indentation of hydrated biological tissues

Fluid flow in biological tissues is important in both mechanical and biological contexts. Given the hierarchical nature of tissues, there are varying length scales at which time-dependent mechanical behavior due to fluid flow may be exhibited. Here, spherical nanoindentation and microindentation testings are used for the characterization of length scale effects in the mechanical response of hydrated tissues. Although elastic properties were consistent across length scales, there was a substantial difference between the time-dependent mechanical responses for large and small contact radii in the same tissue specimens. This difference was far more obvious when poroelastic analysis was used instead of viscoelastic analysis. Overall, indentation testing is a fast and robust technique for characterizing the hierarchical structure of biological materials from nanometer to micrometer length scales and is capable of making quantitative material property measurements to do with fluid flow. © 2011 Materials Research Society.

Biomimetic calcium carbonate-gelatin composites as a model system for eggshell mineralization

The composite nature of mineralized natural materials is achieved through both the microstructural inclusion of an organic component and an overall microstructure that is controlled by templating onto organic macromolecules. A modification of an existing laboratory technique is developed for the codeposition of a CaCO3-gelatin composite with a controllable organic content. First, calibration curves are developed to determine the organic content of a CaCO3-gelatin composite from infrared spectra. Second, a CaCO3-gelatin composite is deposited on either glass coverslips or demineralized eggshell membranes using an automated alternating soaking process. Electron microscopy images and use of the infrared spectra calibration curves show that by altering the amount of gelatin in the ionic growth solutions, the final organic component of the mineral can be regulated over the range of 1-10%, similar to that of natural eggshell. © 2012 Materials Research Societ.

Thermal evolution of Er silicate thin films grown by rf magnetron sputtering

Stoichiometric Er silicate thin films, monosilicate (Er2SiO 5) and disilicate (Er2Si2O7), have been grown on c-Si substrates by rf magnetron sputtering. The influence of annealing temperature in the range 1000-1200 °C in oxidizing ambient (O 2) on the structural and optical properties has been studied. In spite of the known reactivity of rare earth silicates towards silicon, Rutherford backscattering spectrometry shows that undesired chemical reactions between the film and the substrate can be strongly limited by using rapid thermal treatments. Monosilicate and disilicate films crystallize at 1100 and 1200 °C, respectively, as shown by x-ray diffraction analysis; the crystalline structures have been identified in both cases. Moreover, photoluminescence (PL) measurements have demonstrated that the highest PL intensity is obtained for Er2Si2O7 film annealed at 1200 °C. In fact, this treatment allows us to reduce the defect density in the film, in particular by saturating oxygen vacancies, as also confirmed by the increase of the lifetime of the PL signal. © 2008 IOP Publishing Ltd.

The influence of stoichiometry on the structural stability and on the optical emission of erbium silicate thin films

We report the effects of thermal annealing performed in N2 or O2 ambient at 1200 °C on the structural and optical properties of Er silicate films having different compositions (Er2Si O 5,Er2 Si2 O7, and their mixture). We demonstrate that the chemical composition of the stoichiometric films is preserved after the thermal treatments. All different crystalline structures formed after the thermal annealing are identified. Thermal treatments in O 2 lead to a strong enhancement of the photoluminescence intensity, owing to the efficient reduction of defect density. In particular the highest optical efficiency is associated to Er ions in the α phase of Er 2 Si2 O7. © 2008 American Institute of Physics.

Synthesis and luminescence properties of erbium silicate thin films

We have studied the structure and the room temperature luminescence of erbium silicate thin films deposited by rf magnetron sputtering. Films deposited on silicon oxide layers are characterized by good structural properties and excellent stability. The optical properties of these films are strongly improved by rapid thermal annealing processes performed in the range of temperature 800-1250 °C. In fact through the reduction of the defect density of the material, a very efficient room temperature photoluminescence at 1535 nm is obtained. We have also investigated the influence of the annealing ambient, by finding that treatments in O2 atmosphere are significantly more efficient in improving the optical properties of the material with respect to processes in N2. Upconversion effects become effective only when erbium silicate is excited with high pump powers. The evidence that all Er atoms (about 1022 cm-3) in erbium silicate films are optically active suggests interesting perspectives for optoelectronic applications of this material. © 2007 Elsevier B.V. All rights reserved.

Anisotropic behaviour in the magnetic field dependence of the low temperature electrical resistance of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering

We report about the magnetoresistive properties of calcium-doped lanthanum manganate thin films grown by RF magnetron sputtering on single crystalline LaAlO3 and MgO substrates. Two orientations of the magnetic field with respect to the electrical current have been studied: (i) magnetic field in the plane of the film and parallel to the electrical current, and (ii) magnetic field perpendicular to the plane of the film. The film grown on LaAlO 3 is characterised by an unusual magnetoresistive behaviour when the magnetic field is applied perpendicular to the film plane: the appearance of two bumps in the field dependence of the resistance is shown to be related to the occurrence of anisotropic magnetoresistive effects in manganate films. © 2004 Elsevier B.V. All rights reserved.

Impact of hydrated magnesium carbonate additives on the carbonation of reactive MgO cements

Reactive magnesia (MgO) cements have emerged as a potentially more sustainable and technically superior alternative to Portland cement due to their lower production temperature and ability to sequester significant quantities of CO2. Porous blocks containing MgO were found to achieve higher strength values than PC blocks. A number of variables are investigated to achieve maximum carbonation and associated high strengths. This paper focuses on the impact of four different hydrated magnesium carbonates (HMCs) as cement replacements of either 20 or 50%. Accelerated carbonation (20 C, 70-90% RH, 20% CO2) is compared with natural curing (20 C, 60-70% RH, ambient CO2). SEM, TG/DTA, XRD, and HCl acid digestion are utilized to provide a thorough understanding of the performance of MgO-cement porous blocks. The presence of HMCs resulted in the formation of larger size carbonation products with a different morphology than those in the control mix, leading to significantly enhanced carbonation and strength. © 2013 Elsevier Ltd.

Characterization of light and heavy hydrated magnesium carbonates using thermal analysis

Upon heating, hydrated magnesium carbonates (HMCs) undergo a continuous sequence of decomposition reactions. This study aims to investigate the thermal decomposition of various commercially produced HMCs classified as light and heavy, highlight their differences, and provide an insight into their compositions in accordance with the results obtained from thermal analysis and microstructure studies. An understanding of the chemical compositions and microstructures, and a better knowledge of the reactions that take place during the decomposition of HMCs were achieved through the use of SEM, XRD, and TG/differential thermal analysis (DTA). The quantification of their CO 2 contents was provided by TG and dissolving the samples in HCl acid. Results show that variations exist within the microstructure and decomposition patterns of the two groups of HMCs, which do not exactly fit into the fixed stoichiometry of the known HMCs in the MgO-CO2-H2O system. The occurrence of an exothermic DTA peak was only observed for the heavy HMCs, which was attributed to their high CO2 contents and the relatively delayed decomposition pattern. © 2013 Akadémiai Kiadó, Budapest, Hungary.