Calcium Carbonate In Water Research Articles

Abstract 1744: Injectable alginate scaffolds for the dual delivery of Minocycline and Temozolomide for the treatment of glioblastoma

Abstract Glioblastoma Multiforme (GBM) is the most frequent and aggressive malignant primary brain tumor in adults with a life expectancy of less than fifteen months after diagnosis. The standard care for GBM includes surgical resection followed by radiotherapy and chemotherapy. Despite advances in the different methods of therapy, the prognosis for gliomas has not been dramatically improved through the years due to high levels of reoccurrence therefore, alternative treatment methods are needed for GBM. Minocycline (MINO) is a common antibiotic with potential anticancer effects by acting as an anti-angiogenic agent which can help in the treatment and reduction of gliomas by reducing blood vessel formation. Temozolomide (TMZ) is a chemotherapy alkylating agent that has demonstrated antitumor activity against highly resistant malignancies as high-grade gliomas. Injectable alginate scaffolds can serve as a local delivery system for controlled drug release and can be an important component for the development of a treatment method against GBM. The objective of this study was to investigate the optimal concentration of TMZ and MINO alone or in combination against glioblastoma cells (U87-MG) and human umbilical vein endothelial cells (HUVEC) and to evaluate the ability of an injectable alginate scaffold to control the rate of drug release for the treatment of GBM. In this study, U87-MG were treated with MINO (0-4000 µM) and TMZ (0-6000 µM), while HUVEC were treated with MINO (0-1000 µM) and TMZ (0-2000 µM) alone or in combination and a MTT assay was used to determine cell viability. Injectable alginate scaffolds were fabricated by dissolving sodium alginate and calcium carbonate in water and then homogenized with glucanolactone and drugs for 20 seconds. The mixture was then injected into a 24-well plate. After fabrication, scaffolds with MINO, TMZ and MINO/TMZ were incubated in PBS at 37 °C. At each timepoint (1, 4, 7, 10 and 14 days), the amount of drug released was measured by reading the absorbance of MINO and TMZ at 350 and 327 nm, respectively using a microplate reader. The 50% inhibitory concentration (IC50) of MINO and TMZ were found to be 950 µM and 900 µM, respectively in U87-MG. In HUVEC, the IC50 of MINO and TMZ were found to be 150 µM and 400 µM, respectively. MINO and TMZ alone reduced cell viability by 39% and 41%, respectively, in U87-MG and in HUVEC by 36% and 34%, respectively. In combination, both drugs reduced cell viability in U87-MG by 58% and in HUVEC by 56%, resulting in synergistic effects for both cell lines. In addition, the application of the injectable alginate scaffold resulted in a controlled release of the drugs alone or in combination. In conclusion, the combination of MINO and TMZ resulted in synergistic effects on cell viability in both cell lines and the controlled delivery of both drugs with an injectable scaffold can be a promising method for the treatment of GBM. Citation Format: Marco A. Arriaga, Rene N. Rico, Kaitlyn D. Ybanez, Daniela Lopez-Lorenzo, Sue Anne Chew. Injectable alginate scaffolds for the dual delivery of Minocycline and Temozolomide for the treatment of glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1744.

Water Source Heat Pump’s Stuck Problems and Solutions

This paper analyses the water source heat pump’s normal stuck reasons, and test each of them. Identify the main reasons of the stuck pump is pump mechanical seal dynamic ring and static ring binding problems. (Poor water quality, water calcium carbonate, magnesium carbonate grind through the dynamic and static ring, after a long time stop, static ring long force extrusion contact, static ring binding surface molecular diffusion migration adhesion), due to the two rings’ binding, rotating torque beyond the motor starting torque, make the motor can’t start normally. This paper aims to find the real cause of the dynamic ring absorption, and put forward subsequent rectification measures to prevent recurrent stuck.

Ion Pairing and Multiple Ion Binding in Calcium Carbonate Solutions Based on a Polarizable AMOEBA Force Field and Ab Initio Molecular Dynamics.

The speciation of calcium carbonate in water is important to the geochemistry of the world's oceans and has ignited significant debate regarding the mechanism by which nucleation occurs. Here, it is vital to be able to quantify the thermodynamics of ion pairing versus higher order association processes in order to distinguish between possible pathways. Given that it is experimentally challenging to quantify such species, here we determine the thermodynamics for ion pairing and multiple binding of calcium carbonate species using bias-enhanced molecular dynamics. In order to examine the uncertainties underlying these results, we derived a new polarizable force field for both calcium carbonate and bicarbonate in water based on the AMOEBA model to compare against our earlier rigid ion model, both of which are further benchmarked against ab initio molecular dynamics for the ion pair. Both force fields consistently indicate that the association of calcium carbonate ion pairs to form larger species is stable, though with an equilibrium constant that is lower than for ion pairing itself.

Effect of Carbon Nanoparticles on the Crystallization of Calcium Carbonate in Aqueous Solution.

Nanofluids have great application prospects in industrial heat exchange systems because they can significantly improve the heat and mass transfer efficiency. However, the presence of nanoparticles in the fluid might also affect the formation and attachment of inorganic scales, such as calcium carbonate, on the heat exchange surface. The effects of carbon nanoparticles on the crystallization of calcium carbonate in aqueous solution were studied by the scale inhibition test, solution analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The results showed that carbon nanoparticles had an excellent surface scale inhibition performance for calcium carbonate, which could effectively prevent the adhesion of scale on the heat exchange surface. The carbon nanoparticles did not affect the solubility of calcium carbonate in water, but changed the crystal form of the precipitated calcium carbonate, making it difficult to adsorb on the heat exchange surface and achieving a surface scale inhibition effect. Carbon nanofluids effectively inhibit the adhesion of calcium carbonate to heat exchange surfaces.

Process for Preparation of Vitamin C and Method for Determination of Vitamin C in Tablets

Procedure for calcium ascorbate (VITAMIN-C) includes such technological steps as reaction of ascorbic acid on calcium carbonate in water. In recent years, the determination of vitamin C has become an important subject in the field of biochemistry and commercial foods.

Thermodynamics and kinetics of methane hydrate formation and dissociation in presence of calcium carbonate

Huge amount of gas hydrate deposits are identified in deep marine sediments, which may be considered as a future source of energy. Since carbonate is one of the major components of marine sediments, in the present study attention has been given to characterize methane hydrate formation and dissociation in presence of calcium carbonate. Experiments were performed with 0%, 2%, 4%, 6% and 10% by weight of calcium carbonate in distilled water. Extensive investigations have been done on pressure-temperature equilibrium behavior of hydrate formation and dissociation at varying concentrations of calcium carbonate. Hydrate formation rate was found to vary with concentration of calcium carbonate as the solubility of calcium carbonate in water is controlled by the presence of simultaneous chemical equilibria involving a high number of species like Ca2+, CO32−, HCO3−, CO2, etc. Induction time for hydrate formation has also been measured at different concentrations of carbonate. Nucleation point for the hydrate formation was observed to be slightly higher at higher concentration of calcium carbonate due to increased heat absorption. Dissociation enthalpy of hydrates was calculated by using Clausius-Clapeyron at different measured conditions. Moles consumption of methane gas during hydrate formation at different concentrations of carbonate was measured using real gas equation and found to be minimum at 10 wt%.

Antiscalant properties of Spergularia rubra and Parietaria officinalis aqueous solutions

The formation of calcium carbonate in water has important implications in industry. Chemical antiscalant is usually used to control scale depositions. Plant extracts have been recently used as new green antiscalant agents, as they can be easily prepared and are environmentally friendly.In this study, stock aqueous solutions of Spergularia rubra and Parietaria officinalis, two plants used in traditional medicine to treat or prevent urolithiasis, were obtained by infusion. The antiscaling properties of these extracts towards CaCO3 formation were tested by using chronoamperometry and Fast Controlled Precipitation methods. The aqueous solution of S. rubra was further fractionated to isolate compounds of lower polarity. Their efficiency towards CaCO3 precipitation was characterized by Fast Controlled Precipitation method. The inhibiting efficiency of this fractionated solution was greater than that of the stock aqueous solution.

ICONE23-2060 WET RESUSPENSION OF INSOLUBLE MATERIAL FROM A BOILING SUMP

Experiments have been conducted using the technical scale THAI test facility to investigate the wet resuspension of aerosols from a boiling sump. One test with a water solution of potassium iodide and cesium chloride salts and two tests with different suspensions of calcium carbonate in water (primary mass-median-diameters of 0.065 μm and 0.9 μm) have been performed. Resuspension was derived by injecting steam at the bottom of the sump. The investigated superficial velocities, ranging from 0.025 m/s to 0.13 m/s, extend previous resuspension of soluble material experiments in the THAI facility to turbulent flow regime. The aerosol released from the boiling sump into the gas space has been measured independently by using an SMPS particle counter and gas scrubbers. The droplet entrainment has been quantified, based on the concentrations of salts resuspended into the gas atmospheric flow. The entrainment derived from the gas scrubber measurements is well in accordance to previous experimental findings obtained in the THAI facility and other test facilities. A significant enrichment of insoluble aerosol concentration inside the droplets has been found. The SMPS results revealed that very small aerosols are dominantly released from a boiling sump which might remain airborne for long times.

Activation of the dissolution of carbonate materials in water by electric impulse discharges

Effect of electric impulse discharges on the equilibrium in the systems calcium carbonate-water and calcium carbonate-water-carbon dioxide was studied.

Evaluation of the Particle Growth of Amorphous Calcium Carbonate in Water by Means of the Porod Invariant from SAXS

A time-resolved SAXS study has been carried out on the formation of amorphous calcium carbonate from supersaturated aqueous solutions at an initial concentration of 5 mmol/L CaCO(3). Particle formation was induced by mixing equal volumes of equinormal CaCl(2) and Na(2)CO(3) solutions with a stopped-flow device installed at the SAXS beamline. The resulting scattering curves were analyzed without any model assumption with respect to the particle shape. The analysis is based on the intercept of the scattering curve, its initial slope, and the Porod invariant. These parameters give access to the average particle mass, the average particle size, and the mass concentration of the particles, respectively. The evolution of particle mass and concentration with time gives access to the trend in the particle number density. The size and mass values were found to be correlated by characteristic exponents. Two different mass values can be used for this correlation: direct use of the intercept of the scattering curve or alternatively a ratio of this intercept with the corresponding Porod invariant. The resulting exponents depend on the particle growth mechanism. These exponents, together with the evolution of the number density, are capable of discriminating between a monomer-addition mechanism and a particle-particle coagulation mechanism as two alternative building mechanisms for the resulting amorphous CaCO(3) nanoparticles. A detailed description of the data analysis and its merit in establishing a particle growth mechanism is presented.

A Molecular Dynamics Study of the Early Stages of Calcium Carbonate Growth

The precipitation of calcium carbonate in water has been examined using a combination of molecular dynamics and umbrella sampling. During 20 ns molecular dynamics trajectories at elevated calcium carbonate concentrations, amorphous particles are observed to form and appear to be composed of misaligned domains of vaterite and aragonite. The addition of further calcium ions to these clusters is found to be energetically favorable and virtually barrierless. By contrast, there is a large barrier to the addition of calcium to small calcite crystals. Thus, even though calcite nanocrystals are stable in solution, at high supersaturations, particles of amorphous material form because this material grows much faster than ordered calcite nanocrystals.

Molecular Dynamics Study of the Solvation of Calcium Carbonate in Water

We performed molecular dynamics simulations of diluted solutions of calcium carbonate in water. To this end, we combined and tested previous polarizable models. The carbonate anion forms long-living hydrogen bonds with water and shows an amphiphilic character, in which the water molecules are expelled in a region close to its C(3) symmetry axis. The calcium cation forms a strongly bound ion pair with the carbonate. The first hydration shell around the CaCO(3) pair is found to be very similar to the location of the water molecules surrounding CaCO(3) in ikaite, the hydrated mineral.

The calcite/water interface: I. Surface charge in indifferent electrolyte media and the influence of low-molecular-weight polyelectrolyte

Suspensions of calcium carbonate in water with an indifferent background electrolyte (NaCl) have been investigated using several techniques. Particular attention was paid to the dissolution of calcite at equilibrium and as a function of sodium polyacrylate (NaPA) concentration. Also of interest was how this affects the magnitude of the surface charge and the zeta potential. The development of the interfacial charge is discussed with respect to the dissolved species and with regard to the kinetics of dissolution. The partial pressure of CO 2 in solution is believed to play a major role in determining the sign of the charge at equilibrium. In addition to effectively stabilizing calcite suspensions, NaPA was also found to act as a chelating agent at the calcite surface, enhancing the dissolution. The order of addition of NaPA to the suspensions was found to be important.

Efficient large scale stereoinversion of ( R)-ethyl 3-hydroxybutyrate

A three step method for the large scale preparation of enantiomerically pure ethyl ( S)-3-hydroxybutyrate is reported starting from the commercial biopolymer poly[( R)-hydroxybutyrate]. The key step depends on the ability to cleanly invert the stereochemistry of ( R)-ethyl 3-hydroxybutyrate via its mesylate ester under neutral conditions, avoiding the competing elimination process. This has been achieved in good (75%) yield on >100 g scale by controlled addition of the mesylate to a stirred slurry of calcium carbonate in water at 80 °C.

Prediction of Dispersion Characteristics and Rheology in Dense Slurries.

The prediction of slurry viscosity for the suspensions with and without particle size distribution has become possible by using the suspension rheology model proposed in this study. The viscosity prediction model is based on Simha’s cell model, which is applicable to completely dispersed systems. It was certified experimentally that the Simha’s model was able to predict the slurry viscosity for the case of the suspensions with particle size distribution. The present suspension rheology model adopted the assumption that the effect of agglomeration appeared only for the cluster formation with the minimum sized particles, and the other larger particles were completely dispersed. Usui previously proposed the same type model, but the model is modified to give more accurate viscosity predictions. The present model makes the assumption that multi-breakup of inter-particle bonding occurs when a cluster breaks into two parts under a simple shear flow. It is demonstrated that the present model combined with the Simha’s cell model can be successfully used to predict the rheological behavior of slurries.Prediction of the maximum packing volume fraction with non-spherical particles has been one of the important problems in powder technology. The sphericity depending on the particle diameter was measured by means of an image processing instrument. An algorithm to predict the maximum packing volume fraction with non-spherical particles was proposed. The maximum packing volume fraction was used to predict the slurry viscosity with completely dispersed condition. For this purpose, Simha’s cell model was applied for the concentrated slurry with wide particle size distribution. Also, Usui’s model developed for aggregative slurries was applied to predict the non-Newtonian viscosity of dense calcium carbonate-water slurry and fly ash slurry. It was certified that the maximum packing volume fraction for non-spherical particles can be successfully used to predict the slurry viscosity, and this means indirectly the maximum packing volume fraction determined in this study may be reasonable.

Influences of T, S and PCO2 on the pseudo-homogeneous precipitation of CaCO 3 from seawater: implications for whiting formation

The influences of temperature, salinity and P CO 2 on the pseudo-homogeneous nucleation of calcium carbonate from natural seawater were investigated to determine if whitings could be produced by this mechanism under ‘reasonable’ natural conditions. Increasing temperature and salinity substantially raises the P CO 2 at which calcium carbonate nucleation can occur. The saturation state of the water, at which precipitation takes place, is essentially independent (range 20–25 times with respect to calcite) of temperature and salinity, from 25 to 40°C and for S = 35–70 psu. These findings indicate that formation of whitings on the Great Bahama Bank are unlikely to be due to the nucleation of calcium carbonate. However, whitings observed near the Trucial Coast of the Persian Gulf could possibly be the result of direct nucleation of calcium carbonate in waters of lowered P CO 2 associated with phytoplankton blooms.

The rate and mechanism of polymorphic transformation of calcium carbonate in water

The transformations of vaterite and aragonite to calcite in water were investigated at temperatures ranging from 25.0 to 80.0°C and ion activities of Ca2+ and CO2-3 ranging from 10-2.5 M to 10-4.1 M and 10-4.1 M to 10-5.7 M, respectively. It was conf irmed that these transformations proceeded by the dissolution of the metastable phases (vaterite and aragonite) and the growth of calcite, and that the rate-determining step was the growth of calcite for the both transformations. The rate constant of transformation was in good agreement with that of calcite growth from supersaturated solutions. The apparent activation energy of the transformation is about 70 kJ mol-1 and suggests that the rate of transformation of metastable phase is controlled by the surface reaction of calcite growth. The transformation rate of vaterite is independent of the activities of Ca2+ and CO2-3 ions under most conditions. The transformation is considerably retarded in solutions with very high pH (>10) and low concentration of total carbonate ion. Li+ strongly retards the transformation, whereas other alkali metal ions and Cl-, Br- and NO-3 scarcely affect the transformation rate. The incorporation of Li+, having a small ionic radius, is thought to cause a lattice strain on the surface of calcite and thus causes the retardation.

Oxidation states of plutonium in carbonate-rich natural waters

Adsorption of actinide elements to calcium carbonate in waters of moderate to high carbonate concentration has been shown to be dependent on the oxidation state. This property has been exploited for distinguishing the (III) and (IV) oxidation states of plutonium. Ambient plutonium in Mono Lake, California, a natural high-carbonate water, appeared to be entirely in the (IV) oxidation state. Tracer experiments in carbonate media and in Mono Lake water, in the presence of atmospheric oxygen, confirmed that Pu(III) is rapidly oxidized under these conditions.

The formation and transformation mechanism of calcium carbonate in water

Highly supersaturated solutions of Ca 2+ and CO 2− 3 ions rapidly precipitate amorphous calcium carbonate, ACC, the logarithmic thermodynamic solubility product of which is about −6.0 at 25°C. The ACC initially formed is transformed to a mixture of several crystalline calcium carbonate polymorphs within several minutes. The transformed polymorphs are vaterite and calcite at low temperature (14 to 30°C), and aragonite and calcite at high temperature (60 to 80°C). At intermediate temperatures (40 to 50°C) the formation of all three polymorphs was observed. Metastable polymorphs are gradually transformed to the stable form, calcite. It takes about 200 min at 25°C and 370 min at 30°C for the complete transformation of vaterite to calcite, and 1000–1300 min for that of aragonite to calcite at 60–80°C. At 50°C, vaterite is predominantly transformed at first to aragonite within 60 min, and then the aragonite is transformed to calcite in about 900 min. The results of the change in the ion activity product of the solution and the abundances of the polymorphs strongly suggest that the polymorphic transformation of vaterite and aragonite to calcite takes place through dissolution of the metastable phase and growth of the stable phase, calcite. The rate-determining step of the transformation is the growth of calcite. The relative abundance of vaterite becomes higher at 25°C with increasing concentrations of calcium and carbonate ions in the supersaturated solution. When the ion activity product of the initial supersaturated solution is lower than the solubility product of ACC at 25°C, only vaterite directly precipitates after some induction period. The vaterite crystals formed are free of calcite seeds and the vaterite saturated solutions are stable for several days.

Temperature and Ionic Strength Corrections to the Langelier Index—Revisited

The saturation state of calcium carbonate in water has been determined for years by use of the Langelier Index. The US Environmental Protection Agency today specifies its use by water suppliers. Yet the 40‐year‐old chemistry that fostered popular, simplified versions of the index has undergone substantial evolution. Some chemists believe correction factors for temperature and ionic strength can be updated with knowledge gained from activity coefficient and calcium carbonate research. Calculations presented here show wide discrepancies between temperature correction factors derived from initial and more recent research on calcium carbonate solubility. They are most pronounced in the temperature range of primary concern in potable water supplies.