RESUMEN
Sodium silicate solutions, also known as waterglass, have been found to have remarkable utility in a variety of applications. The cumulative weight of evidence from 70 years of varied analysis indicates that silicate solutions consist of a wide range of species, from monomers through oligomers, up to colloids. Moreover, the structure and distribution of these species are greatly dependent upon many parameters, such as solute concentrations, silica to alkali ratio, pH, and temperature. The most interesting and characteristic property of silicate solutions is their ability to form silica gels. Overall, despite extensive research using different spectroscopic and scattering techniques, many questions related to sodium silicate's dynamic structure, stability, polymerization, and gelation remain difficult to answer. The multitude of simultaneous reactions which restructure the silicate species at the atomic scale in response to variation in solution and environmental parameters, makes it difficult to investigate the individual events using only experimental data. Molecular modelling provides an alternative way to study the unknown areas in the aqueous silicate and silica gel systems, generating key insights into the chemical reactions at microscopic length scales. However, sufficient sampling remains a challenge for the practical use of molecular simulation for these systems. Based on both experimental and modelling studies, this review provides a detailed discussion over the structure and speciation of sodium silicate solutions, their gelation mechanism and kinetics, and the syneresis phenomenon. The goal is not only to review the current level of understanding of sodium silicate solutions, silica gels and characterization techniques suitable for studying them, but also to identify the gaps in the literature and open up opportunities for advancing knowledge about these complex systems. We believe that the future direction of research should be toward correlating atomistic, molecular, and meso-scale level details of interactions and reactions in silicate solution and establishing a fundamental understanding of its gelation mechanism and kinetics. We believe that this knowledge could eliminate the "trial and error" approach in manufacturing, and improve structural control in the synthesis of important materials derived from these solutions, such as silica gels and zeolites.
RESUMEN
BACKGROUND: Intrauterine growth factor (IUGR) is one of the most important causes of neonatal mortality. The aim of this study was to evaluate the therapeutic effect of utrogestan on the treatment of IUGR and its complications. MATERIALS AND METHODS: In this clinical trial, 66 pregnant women with idiopathic IUGR embryos were enrolled. Patients in the intervention group, in addition to receiving routine treatment of control group (high-protein diet, resting), took utrogestan capsules (100 mg) twice daily. The primary and secondary outcomes of the disease were recorded in a checklist. Data were analyzed using SPSS 18 using an independent t-test, Chi-square test, and Fisher's exact test. RESULTS: In the intervention group, mean neonatal weight (P = 0.003), mean neonatal Apgar score (P = 0.001), and mean gestational age at birth (P = 0.001) were significantly higher than those in the control group. There was no neonatal death in the intervention group, whereas in the control group, four cases of neonatal death were observed (P = 0.03). In the majority of subjects in the intervention group, resistance index, and pulsatility index of the umbilical artery decreased (P = 0.002). The difference in abdominal circumference and gestational age in the intervention group decreased (P = 0.01). In the intervention group, the diastolic flow of the umbilical artery increased (P = 0.002). CONCLUSION: Utrogestan was effective as an inexpensive and effective way to treat IUGR and improve pregnancy outcomes.
RESUMEN
In this study porous scaffolds of chitosan (CS) and carboxymethyl cellulose (CMC) reinforced with whisker-like biphasic and triphasic calcium phosphate fibers were fabricated by freeze drying method. The effect of addition of CMC, fiber type and content on the mechanical, physicochemical and biological properties of the composite scaffolds was evaluated. The fibers were synthesized by homogenous precipitation method and were characterized. Biphasic fibers contained two phases of hydroxyapatite (HA) and monetite, and triphasic fibers consisted of HA, ß-tricalcium phosphate and calcium pyrophosphate and were 20-270⯵m and 20-145⯵m in length, respectively. The composite scaffolds exhibited desirable microstructures with high porosity (61-75%) and interconnected pores in range of 35-200⯵m. Addition of CMC to CS led to a significant improvement in the mechanical properties (up to 150%) but did not affect the water uptake ability and biocompatibility. Both fibers improved the in vitro proliferation, attachment and mineralization of MG63 cells on scaffolds as evidenced by MTT assay, DAPI staining, SEM and Alizarin red staining. Triphasic fibers were more effective in reinforcing the scaffolds and resulted in higher cell viability. Composite scaffolds of CS and CMC reinforced with 50â¯wt% triphasic fibers were superior in terms of mechanical and biological properties and showed compressive strength and modulus of 150â¯kPa and 3.08â¯MPa, respectively, which is up to 300% greater than pure CS scaffolds. The findings indicate that the developed composite scaffolds are potential candidates for bone tissue engineering although they need further enhancement in mechanical properties.