Nanohydroxyapatite synthesis using optimized process parameters for load-bearing implant

In this study, nanohydroxyapatite (NHA) was synthesized using calcium nitrate tetrahydrate and diammonium hydrogen phosphate via the precipitation method assisted with ultrasonication. Three independent process parameters: temperature (T) (70, 80 and 90°C), ultrasonication time (t) (20, 25 and 30 min), and amplitude (A) (60, 65 and 70%) were studied and optimized using response surface methodology based on 3 factors and 5 level central composite design. The responses of the model were analysed with the help of the particle size measured from field-emission scanning electron microscopy and Brunauer–Emmett–Teller (BET). The surface area of particle was measured with BET and the thermal stability of the powder was measured using thermogravimetric analysis. Finally, with the optimized process parameters obtained from the model, the NHA powder was synthesised and validated against the predicted value. The results show a good agreement with an average error 8% between the actual and predicted values. Moreover, the thermal stability and porosity of synthesized NHA was further improved after calcination. This improvement could be due to the removal of impurities from the NHA powder after calcination as indicated by the Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy.     

Effect of chemical composition and alumina content on structure and properties of ceramic insulators

In the present work, six electrical porcelain compositions with different amount of alumina and silica have been prepared and fired in an industrial furnace at 1300 °C. Density, porosity, bending strength and electrical strength were measured in the samples. In order to find a relationship between properties and sample microstructures, samples were analyzed by scanning electron microscope (SEM) and x-ray diffraction (XRD) techniques. The results showed that, with chemical composition of 53·5 wt.% SiO₂ and 37·5 wt.% alumina, highest electrical strength of 21·97 kV/mm was achieved in fabricated electrical porcelains. Increasing amount of alumina up to 30 wt.% decreases quartz and cristobalite phases, but increases corundum phase 3 to 5 times. SEM observation revealed that dense particles and uniform distribution of long and thin needle shaped mullite are predominant in sample microstructures with highest electrical strength.     

Stability of a Hurwitz polynomial under coefficient perturbations: necessary and sufficient conditions

Necessary and sufficient conditions for a perturbed polynomial to remain Hurwitz are given. The conditions allow considerable freedom in allocating different weights to various coefficients to reflect different levels of uncertainty in the coefficients. The new conditions are an extension of a previous result of the author in which sufficient conditions for the same problem were obtained.     

Determination of chloride, nitrate and calcium ions in sugar with ion selective-electrodes

Chloride, nitrate, and calcium ion-selective electrodes were tested and found satisfactory for the determination of the corresponding ions in highly refined white sugar, molasses and other impure sugar samples at different stages of sugar manufacturing or refining. The interferences by Br⁻ and I⁻ ions in Cl⁻ determination were eliminated by oxidation with 3 M HNO₃ and passing air to remove the free Br₂ and I₂ formed. The Cl⁻ concentration was then determined with a chloride-selective electrode against a calibration curve. Chloride should not be determined by ashing sugar, since this causes high losses of Cl⁻. It was found that NO₃⁻ and free Ca²⁺ ions could be determined directly in the sugar solution against corresponding calibration curves. Total calcium was determined after ashing of sugar samples. The ash was dissolved in 0.1 M HCl and passed through an anion exchange resin to remove PO³⁻₄ and SiO₂₋₃ ions, and Ca²⁺ was determined as before. Bound calcium was obtained by subtracting values of free from total calcium. Determination of bound calcium was useful to monitor the process of liming. For comparison, the three ions were also determined with acceptable precision without removing interfering ions using the method of standard addition and Gran's plot. The errors of determination for both direct and standard addition techniques were 3% for Cl⁻ and NO⁻₃ and 1–5% for Ca²⁺.     

Moisture Sorption Studies on Garlic Powder

The moisture sorption isotherms of two samples of garlic powder, one containing corn starch (CS) and the other without starch, were deter-mined using saturated salt solutions. Monolayer values were calculated from the isotherms using the Brunauer, Emmett and Teller (BET) equation. The addition of CS at 5% slightly increased the monolayer value of the garlic powder, but it had little effect on the caking behavior of the powder. Equilibrium relative humidity (ERH) of garlic powder corresponding to the monolayer value was found to be 14%.     

Expression analysis of <i>OsSERK</i>, <i>OsLEC1</i> and <i>OsWOX4</i> genes in rice (<i>Oryza</i> sativa L.) callus during somatic embryo development

Somatic embryogenesis is an asexual reproduction process that occurs in many plant species, including rice. This process contains several totipotency markers such as Somatic Embryogenesis Receptor-like Kinase (SERK), Leafy Cotyledon1 (LEC1) and WUSCHEL-Related Homeobox4 (WOX4) and also a helpful model for embryo development and clones and transformations. Here, we report the gene expression during somatic embryo development correlates with regeneration frequency in 14 Javanica rice (pigmented and non-pigmented) using modifified N6 media supplemented with Kinetin (2.0 mg/L) and NAA (1.0 mg/L). Although there have been advances in understanding the genetic basis of somatic embryogenesis in other varieties, rice is still unexplored, especially during somatic embryo development. Moreover, for the formation of callus induction from immature embryos, 2,4-D (2.0 mg/L, 3.0 mg/L) was used. This study analysed the gene expression of OsSERK, OsWOX4 and OsLEC1 genes through RT-PCR analysis. Higher expression of the OsLEC1 gene indicates that their function may correlate in the in vitro with the high response of rice after transfer to regeneration media. This study found that rice varieties of pigmented rice (MS Pendek and Gogoniti II) and non-pigmented rice (Pandan Ungu) showed high regeneration frequency, showing higher OsLEC1 expression than other varieties because OsLEC1 promotes the maturation of somatic embryos in plant regeneration on day 14. However, the contrast with Genjah nganjuk may be effective because of other regulatory genes. RT-PCR analysis showed OsSERK had less expression level than OsLEC1 and OsWOX4 in the varieties, which correlate with the percentage of plant regeneration, but not for Gogoniti II. In conclusion, the higher percentage of plant regeneration correlates with the higher expression level of OsLEC1 at day 14 of media regeneration of rice.     

Fungal assembly of L-asparaginase using solid-state fermentation: a review

Because of its antitumor therapeutic-activity, as well as its application in food industries to improve the quality,L-asparaginase has attracted considerable attention from several investigators. In recent years, fungi have occupiedadvanced rank among microorganisms in the production process of the enzyme. This review is spotting the light onthe advantages of fungal enzyme and its applications in the food industry and medications. The solid-statefermentation was discussed as the wide alternative and most accepted biosynthesis technique. However, some lightswere also spotted to the statistical experimental design of the fermentation process, mainly on the methodology of theresponse surface for L-asparaginase biosynthesis by fungi. Finally, the immobilization of the enzyme and the featuresof the widely used solid substrates for the maximization of the production process were explored.