Explore the vast range of titles available.

Montmorillonite is a layered clay mineral whose modification by pillaring, i.e., insertion of oxide nanoclusters between the layers, yields porous materials of great potential in sorption and catalysis. In the present study, an unrefined industrial bentonite from Kopernica (Slovakia), containing ca. 70% of montmorillonite, was used for the preparation of Ti-, Zr-, and mixed [Ti,Zr]-pillared clay sorbents. The pillared samples were characterized with X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and N[sub.2] adsorption at −196 °C and tested for the capacity of CO[sub.2] sorption at 0 °C and 1 bar pressure. The experiments revealed that pillared samples sorbed at least four times more CO[sub.2] than the parent bentonite. Of the materials tested, the sample pillared with mixed [Ti,Zr] oxide props showed the best performance, which was attributed to its superior microporosity. The results of CO[sub.2] adsorption demonstrated that the cost-effective use of crude industrial bentonite as the sorbent precursor is a viable synthesis option. In another experiment, all pillared montmorillonites were subjected to 24 h exposure at room temperature to a flow of dry CO[sub.2] and then tested using simultaneous thermal analysis (STA) and the mass spectrometry (MS) analysis of the evolving gases (STA/QMS). It was found that interaction with dry CO[sub.2] reduces the amount of bound carbon dioxide and affects the processes of dehydration, dehydroxylation, and the mode of CO[sub.2] binding in the pillared structure.

A topological index as a graph parameter was obtained mathematically from the graph’s topological structure. These indices are useful for measuring the various chemical characteristics of chemical compounds in the chemical graph theory. The number of atoms that surround an atom in the molecular structure of a chemical compound determines its valency. A significant number of valency-based molecular invariants have been proposed, which connect various physicochemical aspects of chemical compounds, such as vapour pressure, stability, elastic energy, and numerous others. Molecules are linked with numerical values in a molecular network, and topological indices are a term for these values. In theoretical chemistry, topological indices are frequently used to simulate the physicochemical characteristics of chemical molecules. Zagreb indices are commonly employed by mathematicians to determine the strain energy, melting point, boiling temperature, distortion, and stability of a chemical compound. The purpose of this study is to look at valency-based molecular invariants for SiO[sub.4] embedded in a silicate chain under various conditions. To obtain the outcomes, the approach of atom–bond partitioning according to atom valences was applied by using the application of spectral graph theory, and we obtained different tables of atom—bond partitions of SiO[sub.4]. We obtained exact values of valency-based molecular invariants, notably the first Zagreb, the second Zagreb, the hyper-Zagreb, the modified Zagreb, the enhanced Zagreb, and the redefined Zagreb (first, second, and third). We also provide a graphical depiction of the results that explains the reliance of topological indices on the specified polynomial structure parameters.

A topological index is a numerical parameter that is derived mathematically from a graph structure. In chemical graph theory, these indices are used to quantify the chemical properties of chemical compounds. We compute the first and second temperature, hyper temperature indices, the sum connectivity temperature index, the product connectivity temperature index, the reciprocal product connectivity temperature index and the F temperature index of a molecular graph silicate network and silicate chain network. Furthermore, a QSPR study of the key topological indices is provided, and it is demonstrated that these topological indices are substantially linked with the physicochemical features of COVID-19 medicines. This theoretical method to find the temperature indices may help chemists and others in the pharmaceutical industry forecast the properties of silicate networks and silicate chain networks before trying.

This publication offers an economically promising method of persistent luminescent silicate glass synthesis that does not involve high temperatures or ready-made (separately synthesized) PeL particles. In this study, we demonstrate the formation of SrAl[sub.2]O[sub.4] doped with Eu, Dy, and B in a SiO[sub.2] glass structure using the one-pot low-temperature sol–gel synthesis method. By varying the synthesis conditions, we can use water-soluble precursors (e.g., nitrates) and a dilute aqueous solution of rare-earth (RE) nitrates as starting materials for SrAl[sub.2]O[sub.4] synthesis, which can be formed during the sol–gel process at relatively low sintering temperatures (600 °C). As a result, translucent, persistently luminescent glass is obtained. The glass shows the typical Eu[sup.2+] luminescence and the characteristic afterglow. The afterglow duration is about 20 s. It is concluded that the slow drying procedure (2 weeks) is optimal for these samples to sufficiently get rid of the excess water (mainlyOH groups) and solvent molecules that can influence the strontium aluminate luminescence properties and have a pernicious effect on the afterglow. It can also be concluded that boron is playing a crucial role in the formation of trapping centers needed for PeL processes in the PeL silicate glass.

A structure hierarchy is developed for chain-, ribbon- and tube-silicate based on the connectedness of one-dimensional polymerisations of (TO 4 ) n − tetrahedra, where T = Si 4+ plus P 5+ , V 5+ , As 5+ , Al 3+ , Fe 3+ , B 3+ , Be 2+ , Zn 2+ and Mg 2+ . Such polymerisations are described by a geometrical repeat unit (with n g tetrahedra) and a topological repeat unit (or graph) (with n t vertices). The connectivity of the tetrahedra (vertices) in the geometrical (topological) repeat units is denoted by the expression c T r ( c V r ) where c is the connectivity (degree) of the tetrahedron (vertex) and r is the number of tetrahedra (vertices) of connectivity (degree) c in the repeat unit. Thus c T r = 1 T r1 2 T r2 3 T r3 4 T r4 ( c V r = 1 V r1 2 V r2 3 V r3 4 V r4 ) represents all possible connectivities (degrees) of tetrahedra (vertices) in the geometrical (topological) repeat units of such one-dimensional polymerisations. We may generate all possible c T r ( c V r ) expressions for chains (graphs) with tetrahedron (vertex) connectivities (degrees) c = 1 to 4 where r = 1 to n by sequentially increasing the values of c and r , and by ranking them accordingly. The silicate ( sensu lato ) units of chain-, ribbon- and tube-silicate minerals are identified and associated with the relevant c T r ( c V r ) symbols. Following description and association with the relevant c T r ( c V r ) symbols of the silicate units in all chain-, ribbon- and tube-silicate minerals, the minerals are arranged into decreasing O:T ratio from 3.0 to 2.5, an arrangement that reflects their increasing structural connectivity. Considering only the silicate component, the compositional range of the chain-, ribbon- and tube-silicate minerals strongly overlaps that of the sheet-silicate minerals. Of the chain-, ribbon- and tube-silicates and sheet silicates with the same O:T ratio, some have the same c V r symbols (vertex connectivities) but the tetrahedra link to each other in different ways and are topologically different. The abundance of chain-, ribbon- and tube-silicate minerals decreases as O:T decreases from 3.0 to 2.5 whereas the abundance of sheet-silicate minerals increases from O:T = 3.0 to 2.5 and decreases again to O:T = 2.0. Some of the chain-, ribbon- and tube-silicate minerals have more than one distinct silicate unit: (1) vinogradovite, revdite, lintisite (punkaruaivite) and charoite have mixed chains, ribbons and/or tubes; (2) veblenite, yuksporite, miserite and okenite have clusters or sheets in addition to chains, ribbons and tubes. It is apparent that some chain-ribbon-tube topologies are favoured over others as of the ~450 inosilicate minerals, ~375 correspond to only four topologically unique graphs, the other ~75 minerals correspond to ~46 topologically unique graphs.

This paper presents a study on the carbonation behaviors of hydraulic and non-hydraulic calcium silicate phases, including tricalcium silicate (3CaO·SiO₂ or C₃S), γ-dicalcium silicate (γ-2CaO·SiO₂ or γ-C₂S), β-dicalcium silicate (β-2CaO·SiO₂ or β-C₂S), rankinite (3CaO·2SiO₂ or C₃S₂), and wollastonite (CaO·SiO₂ or CS). These calcium silicate phases were subjected to carbonation reaction at different CO₂ concentration and temperatures. Thermogravimetric analysis (TGA) tests were performed to quantify the amounts of carbonates formed during the carbonation reactions, which were eventually used to monitor the degree of reactions of the calcium silicate phases. Both hydraulic and non-hydraulic calcium silicates demonstrated higher reaction rate in case of carbonation reaction than that of the hydration reaction. Under specific carbonation scenario, non-hydraulic low-lime calcium silicates such as γ-C₂S, C₃S₂ and CS were found to achieve a reaction rate close to that of C₃S. Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscope (SEM) tests were performed to characterize the carbonation reaction products of the calcium silicate phases. The FTIR spectra during the early stage of carbonation reaction showed formation of calcium silicate hydrate (C–S–H) from C₃S, γ-C₂S, β-C₂S, and C₃S₂ phases with a similar degree of polymerization as that of the C–S–H that forms during the hydration reaction of C₃S. However, upon further exposure to CO₂, these C–S–H phases decompose and eventually converted to calcium-modified (Ca-modified) silica gel phase with higher degree of silicate polymerization. Contradictorily, CS phase started forming Ca-modified silica gel phase even at the early stage of carbonation reaction. This paper also revealed the stoichiometry of the Ca-modified silica gel that formed during the carbonation reaction of the calcium silicate phases using the SEM/energy dispersive spectroscopy (EDS) and TGA results.

Sodium zirconium cyclosilicate (SZC) is an oral potassium (K+)-lowering therapy for adults with hyperkalemia. HARMONIZE Asia (ClinicalTrials.gov identifier: NCT03528681) evaluated the efficacy and safety of SZC in Chinese patients with hyperkalemia. This Phase III, randomized, double-blind, placebo-controlled study recruited patients with serum K+ (sK+) ≥5.1 mmol/L at 35 sites in China. Patients received SZC 10 g three times daily (TID) for 24 or 48 hours during an open-label initial phase (OLP). Those patients achieving normokalemia (sK+ 3.5–5.0 mmol/L inclusive) entered a 28-day randomized (2:2:1) treatment phase (RTP) and received SZC 5 g, SZC 10 g, or placebo once daily. The primary endpoint was mean sK+ during RTP Days 8 to 29. Secondary endpoints included mean change in sK+ during the OLP, the proportion of patients who achieved normokalemia at the end of the OLP, the proportion that maintained normokalemia during the RTP, and time to recurrence of hyperkalemia. In total, 270 patients received SZC 10 g TID during the OLP; 256 (94.8%) completed the OLP. During the OLP, mean sK+ decreased by 1.1 mmol/L from baseline (5.9 mmol/L; P < 0.001) and 87.4% of patients achieved normokalemia. During the RTP, SZC 5 g and 10 g reduced mean sK+ versus placebo in a dose-dependent manner (each P < 0.001); least-squares means (95% confidence interval [CI]) sK+ were 4.9 mmol/L (4.7, 5.0), 4.4 mmol/L (4.3, 4.6), and 5.2 mmol/L (5.1, 5.4) for SZC 5 g, 10 g, and placebo, respectively. At RTP end, the proportions of patients who maintained normokalemia were 58.8% (SZC 5 g; odds ratio vs placebo, 2.5 [95% CI: 1.1, 6.1; P = 0.035]), 76.5% (SZC 10 g; odds ratio vs placebo, 6.3 [95% CI: 2.6, 15.3; P < 0.001]), and 36.8% for placebo. Risk of recurrent hyperkalemia was reduced by 61.0% and 84.0% with SZC 5 g and SZC 10 g, respectively, versus placebo (each P < 0.001). During the RTP, the incidence of adverse events was numerically higher with SZC 5 g (50.0% of patients) and 10 g (44.0%) versus placebo (36.0%); driven primarily by peripheral edema and constipation. Both SZC doses demonstrated clinically relevant and statistically significant, dose-dependent efficacy in managing sK+ levels in Chinese patients with hyperkalemia, compared with placebo. SZC tolerability was broadly aligned with the known safety profile of SZC.

This research was developed to investigate whether inoculation with Azospirillum brasilense in combination with silicon (Si) can enhance N use efficiency (NUE) in wheat and to evaluate and correlate nutritional and productive components and wheat grain yield. The study was carried out on a Rhodic Hapludox under a no-till system with a completely randomized block design with four replications in a 2 × 2 × 5 factorial scheme: two liming sources (with Ca and Mg silicate as the Si source and limestone); two inoculations (control - without inoculation and seed inoculation with A . brasilense ) and five side-dress N rates (0, 50, 100, 150 and 200 kg ha −1 ). The results of this study showed positive improvements in wheat growth production parameters, NUE and grain yield as a function of inoculation associated with N rates. Inoculation can complement and optimize N fertilization, even with high N application rates. The potential benefits of Si use were less evident; however, the use of Si can favour N absorption, even when associated with A . brasilense . Therefore, studies conducted under tropical conditions with Ca and Mg silicate are necessary to better understand the role of Si applied alone or in combination with growth-promoting bacteria such as A . brasilense .

Pozzolanic reaction of volcanic ash with hydrated lime is thought to dominate the cementing fabric and durability of 2000-year-old Roman harbor concrete. Pliny the Elder, however, in first century CE emphasized rock-like cementitious processes involving volcanic ash (pulvis) \"that as soon as it comes into contact with the waves of the sea and is submerged becomes a single stone mass (fierem unum lapidem), impregnable to the waves and every day stronger\" (Naturalis Historia 35.166). Pozzolanic crystallization of Al-tobermorite, a rare, hydrothermal, calcium-silicate-hydrate mineral with cation exchange capabilities, has been previously recognized in relict lime clasts of the concrete. Synchrotron-based X-ray microdiffraction maps of cementitious microstructures in Baianus Sinus and Portus Neronis submarine breakwaters and a Portus Cosanus subaerial pier now reveal that Al-tobermorite also occurs in the leached perimeters of feldspar fragments, zeolitized pumice vesicles, and in situ phillipsite fabrics in relict pores. Production of alkaline pore fluids through dissolution-precipitation, cation-exchange and/or carbonation reactions with Campi Flegrei ash components, similar to processes in altered trachytic and basaltic tuffs, created multiple pathways to post-pozzolanic phillipsite and Al-tobermorite crystallization at ambient seawater and surface temperatures. Long-term chemical resilience of the concrete evidently relied on water-rock interactions, as Pliny the Elder inferred. Raman spectroscopic analyses of Baianus Sinus Al-tobermorite in diverse microstructural environments indicate a cross-linked structure with Al3+ substitution for Si4+ in Q3 tetrahedral sites, and suggest coupled [Al3++Na+] substitution and potential for cation exchange. The mineral fabrics provide a geoarchaeological prototype for developing cementitious processes through low-temperature rock-fluid interactions, subsequent to an initial phase of reaction with lime that defines the activity of natural pozzolans. These processes have relevance to carbonation reactions in storage reservoirs for CO2 in pyroclastic rocks, production of alkali-activated mineral cements in maritime concretes, and regenerative cementitious resilience in waste encapsulations using natural volcanic pozzolans.