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[en] Lactic acid bacteria (LAB) have been used for food fermentation due to its fermentative ability to improve and enhance the quality of the end food products. However, the performance of LAB is affected as fermentation time elapsed because the microbial growth is inhibited by its end product, for example lactic acid. In this study, a new approach was introduced to reduce the product inhibition effect using CaCO_3 which is encapsulated in spherical liquid core capsules of diameter 3.5 mm and 3.6 mm produced through extrusion dripping method. The results showed that the pH and lactic acid concentration of LAB fermentation was well maintained by the capsules. The results of the fermentation conducted to control pH and lactic acid concentration using the capsules were better than those of the control set and comparable with that of the free CaCO_3 set. In addition, the viable cell concentration of L. casei shirota was high at the end of fermentation when the fermentation was conducted using the capsules. The results of this study suggested that the capsules have high potential to be applied for pH and lactic acid level control in LAB fermentation for various productions. (author)
[en] In order to study the composite fouling characteristics of crystallization and particulate, the fouling characteristics of calcium carbonate (CaCO3) and nanometer magnesia in the alternating elliptical axis tube were investigated experimentally. The results show that CaCO3 has obvious effect on the inhibition of the formation of particulate fouling. The asymptotic value of fouling resistance of the nanometer magnesia is the highest and the CaCO3 is the lowest, and the composite fouling is between them. The fouling rate and the asymptotic value of composite fouling resistance decrease with the increase of the CaCO3 concentration. The time reaches to the asymptotic value of the three experiments are similar. The variation of nanometer magnesia concentration has greater influence than the CaCO3 concentration on the asymptotic value of composite fouling. The fouling rate and the asymptotic value of composite fouling resistance increase obviously with the increase of the nanometer magnesia concentration
[en] Biominerals, the mineralized tissues of animals, plants, and microorganisms, have inspired humanity with their properties and forms since prehistory. Bones and shells have been used for tools, for currency, for symbolic objects and for art in every culture. Both the fascination and the importance that biominerals present for science are made clear in Darwin's nineteenth-century writings, and in D'Arcy Wentworth Thompson's 1917 On Growth and Form, with its memorable cover illustration of the multi-chambered calcium carbonate nautilus shell. Biomineralization is now a field of study in its own right
[en] The processes based on the separation by membranes seem to become very powerful tools for the purification and the retraining of the fluids. Competed by the inverse osmosis in the domain of the desalination of waters, the electrodialysis (ED) occupies a large place in the agro-alimentary industries to treat the co-products on the one hand and to contribute to the retraining of containing sewages of the heavy metals and toxic, on the other hand. Although it is appreciable for cost and reliability in several domains, the ED suffers to scaling problem caused by the concentration of some ions. Since the technique is used currently for the desalination of water in some industries, we have opted to study mechanisms of membrane scaling by calcium carbonate, one of salts the more frequently met in the stations of desalination in Tunisia. The survey uses a method of accelerated scaling of a pilot unit of electrodialysis. By means of this method, we studied the effect of the initial pH and the composition of water on the kinetics of the scaling formation. The treated waters are synthetic solutions. The results showed that the CO2 quantity initially dissolved in the solutions is an important factor in the scaling process. According to the composition of water, domains of CO2 pressure were defined in whom a small variation can generate the rupture of the metastability state in the compartment of concentration and provoke CaCO3 nucleation in the compartment of concentration and/or on the membranes and conducts. The presence in solution of magnesium in only a Ca/Mg ratio of 0,5 delayed considerably the CaCO3 nucleation. This ratio is considered like a low bottom limit of magnesium action, ion to natural inhibitory effect present in the natural waters.
[en] Gallstones of seven patients were collected from different parts of North West Frontier and Punjab provinces. These stones were analyzed using Liebermann-Burchard method, estimation technique and Microlab-200 for cholesterol, calcium carbonate (CaCO/sub 3/) and bilirubinate respectively. The levels of cholesterol bilirubinate and CaCO/sub 3/ were found in the ranges of 50-81, 12-40 and 7-19% respectively. All of the stones were found to be mixed type stones that contain cholesterol, bilirubinate and calcium carbonate. The structures of the stones are also shown in the picture, which confirm our analysis data. Possible reasons, which cause formation of gallstones, are discussed in this paper. (author)
[en] Scale formation is a serious problem encountered in many industrial plants including natural water desalination units. Scales are mainly formed by calcium carbonate . In some ground waters, the presence of some species such as Mg2+, SO42- and Fe2+ influence significantly the CaCO3 precipitation. In the present work, the effects of Fe2+ and Fe3+ on the kinetic precipitation and the microstructure of CaCO3 were investigated. The calcium carbonate was precipitated by using the degassing CO2 method. This technique is based on the elimination of the dissolved carbonic gas CO2 in solution by air or N2 bubbling according to the following precipitation reaction of calcium carbonate: Ca2+2HCO3-→CaCO3+(s)+CO2↑+H2O. In ground Water, iron usually occurs in its ferrous state (Fe2+), but once exposed to air, it will be oxidized to Fe3+. The effect of iron (II) on the carbonate calcium precipitation was been reported under an azote bubbling condition. The experimental procedure used in this work allowed us to study the effect of Fe(II) and Fe(III) on the CaCO3 precipitation. It was shown that the iron ions with these different degrees of oxidation (II or III) improved the kinetic precipitation of calcium carbonate. XRD analysis shows that the presence of iron (II) favoured the formation of aragonite instead of vaterite phase. The microscopic observation by SEM showed that the presence of the iron (II) in the solution affects the morphology and the size of the carbonate calcium precipitate.
[en] Polycrystalline zinc oxide (ZnO) films were successfully deposited on calcite (CaCO/sub 3/) by pulsed laser deposition PLD at room temperature. Zinc metal target (4N purity, analytical grade) was used for laser ablation in ambient O/sub 2/ atmosphere. XRD results show the poly crystallinity of ZnO thin film. Four probe apparatus was used to measure the resistivity of thin film. It was found to have very high resistivity approx 200 M omega m. High resistivity is attributed to the high-quality crystal structure of ZnO. ZnO/sub 2/ was also found to be present in the thin film. These films have great importance in fabrication of gas sensors and other applications. (author)
[en] Understanding of soil phosphorus (P) adsorption chemistry is essential for evolving best fertilizer management practices aimed at enhancing fertilizer P use efficiency and environment quality. Soil chemical parameters which govern P adsorption maxima and binding strength in calcareous and non-calcareous soils were determined. Five soils representing three different parent materials i.e. mixed mineralogy alluvium, loess and non calcareous sandstone were sampled at genetic horizons in each profile. Phosphorus adsorption isotherm was developed for each of the 32 soil samples by equilibration of two g air dry soil with 0 to 4000 mgl/sup -1/ (0 to 125 mM) P in 20 ml of 10 mM KCI; and fitted to Langmuir and Freundlich equations. The chemical parameters i.e. pH, CaCO/sub 3/, total and dissolved organic carbon, exchangeable calcium, dithionite extractable iron (Fe/sub d/) and aluminum (AI/sub d/), oxalate extractable iron (Fe/sub o/) and aluminum (Al/sub o/) and as a test for plant available P extractable with NaHCO/sub 3/ were determined. The Fruendlich equation, an empirical relation between adsorbed and solution P, fitted the adsorption isotherms better than the Langmuir equation which relates adsorption to solid surface coverage by adsorbate. Adsorption maxima at low affinity sites positively correlated with soil CaCO/sub 3/ due to precipitation as Ca-P and to extractable iron oxide; and the binding strength of high affinity (kJ sites correlated positively with soil Fe/sub d/, Al/sub o/, AI/sub d/, and crystalline iron oxide (Fe/sub d/-Fe/sub o/) contents. The Freundlich parameter b/sub r/, adsorption exponent which signifies sorption intensity also positively correlated with soil Fe/sub d/, Fe/sub cr/ and Aid contents. Phosphorus adsorption at its low concentration in equilibrium solution seems to be governed by soil iron oxides and precipitation as Ca-P is important only at high P concentration, less frequently achieved in farm fields. (author)
[en] Continued construction of the realistic phantom for calibration of transuranic isotope lung counters is discussed. Current work includes final shaping of the torso cast, development of a technique for making foamed plastic lungs loaded with transuranic isotopes, casting of tissue-equivalent (T.E.) organs, and acquisition of rib cages for the second and third phantoms