Ion substitution induced formation of spherical ceramic particles

How to precipitate ceramic nano- and microspheres in water based solutions only using inorganic ions is a challenge. In this study, spherical particles of alkaline earth phosphates and fluorides were synthesized using a precipitation reaction. Substituting ions, through inhibition of crystal growth, was used to induce sphere formation and to alter the morphology, size and composition of the spheres. The difference in ionic radius between the substituting ion (Mg, Ca and Sr) and the main cation (Sr and Ba) influenced the critical concentration to allow for sphere formation as well as the crystallinity. The larger difference, the lower was the concentration needed to form spheres. Low concentrations of Mg was enough to generate amorphous spheres of Sr- and Ba-phosphates whereas higher concentrations were needed if the radius difference were smaller. An increasing degree of substitution leads to a decrease in crystallinity of precipitated particles. The degree of substitution was determined to 16–55% where a low degree of ion substitution in the phosphates resulted in the formation of spheres (500–800?nm) with rough surfaces composed of apatite like phases. A higher degree of substitution resulted in amorphous spheres (500?nm- 1?μm) with smooth surfaces.     

Adsorption of Pb and Cd in rice husk and their immobilization in porous glass-ceramic structures

Rice husk, an agricultural waste, is abundantly available in many countries such as China, India, Brazil, US, and South East Asia. Despite the massive production of rice husk, it is mainly disposed to landfill. In this work, utilization of rice husk for a potential waste-water treatment is evaluated, along with subsequent encapsulation of the adsorbed heavy metals (Pb and Cd) inside a porous glass-ceramic. Vitrified bottom ash (another source of waste) was mixed with foaming agents in dif- ferent weight ratios (40:60, 50:50, and 60:40) to prepare a glass matrix for encapsulation of Pb-/Cd-loaded rice husk. It was shown that using 40 wt% vitrified bottom ash with 60 wt% foaming agents leads to a foam glass with the best pore size distribution. Therefore, this batch was further mixed with 70 volume% (5 wt%) heavy metal-loaded rice husk and was heat-treated at 750°C for 3 hours. The final glass-ceramic porous structure was char acterized using SEM, XRD, compression test, and it was shown that it is safe to be used as it passes the EN12457-2 leaching test.     

Correction to: Online Identity Crisis: Identity Issues in Online Communities

Minds and Machines - An amendment to this paper has been published and can be accessed via the original article.     

Assessment of intradialysis calcium mass balance by a single pool variable‐volume calcium kinetic model

Introduction: A reliable method of intradialysis calcium mass balance quantification is far from been established. We herein investigated the use of a single‐pool variable‐volume Calcium kinetic model to assess calcium mass balance in chronic and stable dialysis patients. Methods: Thirty‐four patients on thrice‐weekly HD were studied during 240 dialysis sessions. All patients were dialyzed with a nominal total calcium concentration of 1.50 mmol/L. The main assumption of the model is that the calcium distribution volume is equal to the extracellular volume during dialysis. This hypothesis is assumed valid if measured and predicted end dialysis plasma water ionized calcium concentrations are equal. A difference between predicted and measured end‐dialysis ionized plasma water calcium concentration is a deviation on our main hypothesis, meaning that a substantial amount of calcium is exchanged between the extracellular volume and a nonmodeled compartment. Findings: The difference between predicted and measured values was 0.02 mmol/L (range ?0.08:0.16 mmol/L). With a mean ionized dialysate calcium concentration of 1.25 mmol/L, calcium mass balance was on average negative (mean ± SD ?0.84 ± 1.33 mmol, range ?5.42:2.75). Predialysis ionized plasma water concentration and total ultrafiltrate were the most important predictors of calcium mass balance. A significant mobilization of calcium from the extracellular pool to a nonmodeled pool was calculated in a group of patients. Discussion: The proposed single pool variable‐volume Calcium kinetic model is adequate for prediction and quantification of intradialysis calcium mass balance, it can evaluate the eventual calcium transfer outside the extracellular pool in clinical practice.     

Piperazine and methyldiethanolamine interrelationships in CO2 absorption by aqueous amine mixtures. Part II—Saturation rates of mixed reagent solutions

This work is a companion to a previous article, Part I, published in The Canadian Journal of Chemical Engineering, dealing with CO₂ absorption in aqueous solutions containing a single aminic reagent (specifically methyldiethanolamine (MDEA) or piperazine (PZ)). In this second part, different PZ/MDEA mixtures are experimentally studied and their performances are compared with that of the single reagents. It is indeed well known that small quantities of PZ added to MDEA aqueous solutions are sufficient to obtain a significant improvement in the kinetics of the process. PZ is considered an activator or promoter for MDEA, but the mechanism of this synergy has still not been clearly demonstrated. The aim of this study is an attempt to understand how PZ and MDEA can interact by experimentally analyzing this beneficial mutual effect and by explaining it with the help of a suitable yet not complex model. We believe that the involved chemistry is not more complex than that reported in Part I for the single reagents. According to our findings, it is MDEA that enhances the action of PZ, as opposed to what many authors claim. Moreover, our results seem to rule out the existence of any PZ shuttle effect.     

Ligand Binding to Dynamically Populated G-Quadruplex DNA

Several small-molecule ligands specifically bind and stabilize G-quadruplex (G4) nucleic acid structures, which are considered to be promising therapeutic targets. G4s are polymorphic structures of varying stability, and their formation is dynamic. Here, we investigate the mechanisms of ligand binding to dynamically populated human telomere G4 DNA by using the bisquinolinium based ligand Phen-DC3 and a combination of single-molecule FRET microscopy, ensemble FRET and CD spectroscopies. Different cations are used to tune G4 polymorphism and folding dynamics. We find that ligand binding occurs to pre-folded G4 structures and that Phen-DC3 also induces G4 formation in unfolded single strands. Following ligand binding to dynamically populated G4s, the DNA undergoes pronounced conformational redistributions that do not involve direct ligand-induced G4 conformational interconversion. On the contrary, the redistribution is driven by ligand-induced G4 folding and trapping of dynamically populated short-lived conformation states. Thus, ligand-induced stabilization does not necessarily require the initial presence of stably folded G4s.     

1,2,4-Oxadiazole Topsentin Analogs with Antiproliferative Activity against Pancreatic Cancer Cells,Targeting GSK3β Kinase

A new series of topsentin analogs, in which the central imidazole ring of the natural lead was replaced by a 1,2,4-oxadiazole moiety, was efficiently synthesized. All derivatives were pre-screened for antiproliferative activity against the National Cancer Institute (NCI-60) cell lines panel. The five most potent compounds were further investigated in various pancreatic ductal adenocarcinoma (PDAC) cell lines, including SUIT-2, Capan-1, and Panc-1 cells, eliciting EC₅₀ values in the micromolar and sub-micromolar range, associated with significant reduction of cell migration. These remarkable results might be explained by the effects of these new topsentin analogues on epithelial-to-mesenchymal transition markers, including SNAIL-1/2 and metalloproteinase-9. Moreover, flow cytometric analysis after Annexin V-FITC and propidium iodide staining demonstrated that these derivatives enhanced apoptosis of PDAC cells. Keeping with these data, the PathScan intracellular signaling and ELISA array revealed cleavage of caspase-3 and PARP and a significant inhibition of GSK3β phosphorylation, suggesting this kinase as a potential downstream target of our novel compounds. This was further supported by a specific assay for the evaluation of GSK3β activity, showing IC₅₀ values for the most active compounds against this enzyme in the micromolar range.