Crystal structures and X-ray powder diffraction data for Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6 synthetic leucite analogues

Leucites are tetrahedrally coordinated silicate framework structures with some of the silicon framework cations partially replaced by divalent or trivalent cations. These structures have general formulae A2BSi5O12 and ACSi2O6; where A is a monovalent alkali metal cation, B is a divalent cation, and C is a trivalent cation. In this paper, we report the Rietveld refinements of three more synthetic leucite analogues with stoichiometries of Cs2NiSi5O12, RbGaSi2O6, and CsGaSi2O6. Cs2NiSi5O12 is Ia $\bar{3}$ d cubic and is isostructural with Cs2CuSi5O12. RbGaSi2O6 is I41/a tetragonal and is isostructural with KGaSi2O6. CsGaSi2O6 is $I\bar{4}3d$ cubic and is isostructural with RbBSi2O6.

Calcium-sensing receptor in GtoPdb v.2021.3

The calcium-sensing receptor (CaS, provisional nomenclature as recommended by NC-IUPHAR [47] and subsequently updated [77]) responds to multiple endogenous ligands, including extracellular calcium and other divalent/trivalent cations, polyamines and polycationic peptides, L-amino acids (particularly L-Trp and L-Phe), glutathione and various peptide analogues, ionic strength and extracellular pH (reviewed in [78]). While divalent/trivalent cations, polyamines and polycations are CaS receptor agonists [14, 110], L-amino acids, glutamyl peptides, ionic strength and pH are allosteric modulators of agonist function [36, 47, 61, 108, 109]. Indeed, L-amino acids have been identified as "co-agonists", with both concomitant calcium and L-amino acid binding required for full receptor activation [148, 54]. The sensitivity of the CaS receptor to primary agonists is increased by elevated extracellular pH [18] or decreased extracellular ionic strength [109]. This receptor bears no sequence or structural relation to the plant calcium receptor, also called CaS.

Trivalent Cations Detection of Magnetic-Sensitive Microcapsules by Controlled-Release Fluorescence Off-On Sensor

A pyrene-based derivative, 2-((pyrene-1-ylmethylene)amino)ethanol (PE) nanoparticle, was encapsulated via water-in-oil-in-water (W/O/W) double emulsion with the solvent evaporation method by one-pot reaction and utilized as a fluorescence turn-on sensor for detecting Fe3+, Cr3+, and Al3+ ions. Magnetic nanoparticles (MNPs) embedded in polycaprolactone (PCL) were used as the magnetic-sensitive polyelectrolyte microcapsule-triggered elements in the construction of the polymer matrix. The microcapsules were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) titrations, quantum yield (Φf) calculations, 1H nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), and superconducting quantum interference device magnetometry (SQUID) studies. This novel responsive release of the microcapsule fluorescence of the turn-on sensor for detecting trivalent cations was due to the compound PE and the MNPs being incorporated well within the whole system, and an effective thermal and kinetic energy transfer between the core and shell structure efficiently occurred in the externally oscillating magnetic field. The magnetic-sensitive fluorescence turn-on microcapsules show potential for effective metal ion sensing in environmental monitoring and even biomedical applications. Under the optimal controlled-release probe fluorescence conditions with high-frequency magnetic field treatment, the limit of detection (LOD) reached 1.574–2.860 μM and recoveries ranged from 94.7–99.4% for those metals in tap water.

Liudongshengite, Zn4Cr2(OH)12(CO3)·3H2O, a new mineral of the hydrotalcite supergroup, from the 79 mine, Gila County, Arizona, USA

ABSTRACT A new mineral species, liudongshengite, ideally Zn4Cr2(OH)12(CO3)·3H2O, has been found in the 79 mine, Gila County, Arizona, USA. It occurs as micaceous aggregates or hexagonal platy crystals (up to 0.10 × 0.10 × 0.01 mm). The mineral is pinkish and transparent with white streak and vitreous luster. It is brittle and has a Mohs hardness of ∼1.5, with perfect cleavage on (001). No twinning or parting is observed macroscopically. The measured and calculated densities are 2.95 (3) and 3.00 g/cm3, respectively. Optically, liudongshengite is uniaxial (−), with ω = 1.720 (8), ε = 1.660 (7) (white light). An electron microprobe analysis, combined with the carbon content measured using an elemental combustion system equipped with mass spectrometry, yielded the empirical formula (Zn3.25Mg0.17Cr2.58)Σ6.00(OH)12(CO3)1.29·3H2O, based on (M2+ + M3+) = 6 apfu, where M2+ and M3+ are divalent and trivalent cations, respectively. Liudongshengite belongs to the quintinite group within the hydrotalcite supergroup and is the Cr-analogue of zaccagnaite-3R, Zn4Al2(OH)12(CO3)·3H2O. It is trigonal, with space group Rm and unit-cell parameters a = 3.1111(4), c = 22.682(3) Å, and V = 190.12(4) Å3. The crystal structure of liudongshengite is composed of positively charged brucite-like layers, [M2+1–xM3+x(OH)2]x+, alternating with negatively charged layers of (CO3)2–·3H2O. Compared to other minerals in the quintinite group, liudongshengite is remarkably enriched in M3+, with an M2+:M3+ ratio of 1.33:1. Like zaccagnaite-3R and many other hydrotalcite-type minerals, liudongshengite may also possess polytypes, as a series of synthetic hydrotalcite-type compounds with a general chemical formula [Zn4Cr2(OH)12]X2·4H2O, where X = Cl–, NO3–, or ½ SO42–, but with unit-cell parameters different from those for liudongshengite, have been reported previously.

Role of Environmental Variables in the Transport of Microbes in Stormwater

Microbial pathogens present in stormwater, which originate from human sewage and animal faecal matters, are one of the major impediments in stormwater reuse. The transport of microbes in stormwater is more than just a physical process. The mobility of microbes in stormwater is governed by many factors, such as dissolved organic matter, cations, pH, temperature and water flow. This paper examined the roles of three environmental variables, namely: dissolved organic matter, positive cations and stormwater flow on the transport of two faecal indicator bacteria (FIB), Enterococcus spp. and Escherichia coli. Stormwater runoff samples were collected during twelve wet weather events and one dry weather event from a medium density residential urban catchment in Brisbane. Enterococcus spp. numbers as high as 3 × 104 cfu/100 mL were detected in the stormwater runoff, while Escherichia coli numbers up to 3.6 × 103 cfu/100 mL were observed. The dissolved organic carbon (DOC) in the stormwater samples was in the range of 2.2–5.9 mg/L with an average concentration of 4.5 mg/L in which the hydrophilic carbon constituted the highest mass fraction of 60–80%. The results also showed that the transport of FIB in stormwater was reduced with an increasing concentration of the hydrophilic organic fraction, especially the humic fraction. On the contrary, the concentration of trivalent cations and stormwater flow rate showed a positive correlation with the FIB numbers. These findings indicated the potentiality to make a good use and measurement of simple environmental variables to reflect the degree of microbe transport in stormwater from residential/suburban catchments.

Symmetry relations in wurtzite nitrides and oxide nitrides and the curious case of Pmc21

Binary III–V nitrides such as AlN, GaN and InN in the wurtzite-type structure have long been considered as potent semiconducting materials because of their optoelectronic properties, amongst others. With rising concerns over the utilization of scarce elements, a replacement of the trivalent cations by others in ternary and multinary nitrides has led to the development of different variants of nitrides and oxide nitrides crystallizing in lower-symmetry variants of wurtzite. This work presents the symmetry relationships between these structural types specific to nitrides and oxide nitrides and updates some prior work on this matter. The non-existence of compounds crystallizing in Pmc21, formally the highest subgroup of the wurtzite type fulfilling Pauling's rules for 1:1:2 stoichiometries, has been puzzling scientists for a while; a rationalization is given, from a crystallographic basis, of why this space group is unlikely to be adopted.

Mineral composition of serpentinites of the Kishinskij protrusion (Greater Caucasus)

Ряд ключевых вопросов геологии серпентинитовых массивов Большого Кавказа остается дискуссионным. К их числу относятся формационная принадлежность и геодинамическая типизация протолита апогипербазитов. Необходимым фактическим материалом для обсуждения этих вопросов служат сведения о минеральном составе. Объектом исследований являются серпентиниты Кишинского массива, залегающего в основании Кизилкольского тектонического покрова в зоне Передового хребта Большого Кавказа. Цель работы – получение данных о минеральном составе серпентинитов Кишинского массива, анализ особенностей состава зональных хромшпинелидов, получение данных об условиях формирования и преобразования апогипербазитов. Методы исследования. Рентгенофазовый анализ, электронно-зондовый микроанализ и электронная микроскопия, статистический анализ результатов измерений. Результаты работы. Изучаемые серпентиниты интенсивно дислоцированы. В целом они имеют хризотил-антигоритовый состав. В составе «тектонических окатышей» внутренние части сложены антигоритовыми (с небольшим количеством хризотила) с бруситом разновидностями, внешние части – хризотил-антигоритовыми с клинохлором. По разломам отмечается гидротермальное оталькование, окварцевание и карбонатизация. В серпентинитах присутствуют зональные хромшпинелиды, ядерные части которых представлены алюмохромитом с реликтами хромпикотита, каймы – феррихромитом – хроммагнетитом; локально отмечаются тонкие оторочки магнетита. Метасоматические замещения в хромшпинелидах сопровождались привносом Fe(замещавшего как двух-, так и трехвалентные катионы), Mn, Ni и выносом Mg, Al, Cr, V. Преобразования пород происходили в условиях высокотемпературной зоны зеленосланцевой фации с участием восстановительных флюидов при относительно пониженном отношении флюид/порода. Для ядер значения Cr# составляют ~0,5-0,7, Mg# ~0,4-0,6, что отвечает области составов первичных магматических шпинелей. Судя по составу хромшпинелидов, апогипербазиты связаны с офиолитовой ассоциаций и близки ультрамафитам островодужных обстановок, в том числе серпентинитовым диапирам фронтальных частей островных дуг. При сравнении с серпентинитами расположенного севернее Даховского выступа устанавливается формационное сходство – принадлежность к офиолитам, но в то же время проявляется отличие Р-Т параметров условий метаморфических трансформаций. Several key issues in the geology of the serpentinite massifs of the Greater Caucasus remain debatable. These include formational and geodynamic typing the protolith of apohyperbasites. The necessary factual material for discussing these issues is information about the mineral composition. The object of research is the serpentinites of the Kishinsky massif, which lies at the base of the Kizilkol tectonic cover in the zone of the Peredovoy Range of the Greater Caucasus. The aim of this study was to gather data on serpentinites of Kishinsky massif mineral composition; characteristics analysis of the zonal composition of chromespinelides; to obtain data on the formation conditions and transformation of apohyperbasites. Methods.X-ray phase analysis, electron microprobe analysis and electron microscopy, statistical analysis of measured results. Results. The studied serpentinites are intensively dislocated. Generally, they are of chrysotile-antigorite composition. As part of the "tectonic pellets", the inner parts are composed of antigorite (with a small amount of chrysotile) and brucite varieties, the outer parts are chrysotile – antigorite with clinochlore. Presence of hydrothermal talcose, silicification and carbonatization is noted in the observed faults. There are zonal chromespinelides in serpentinites where nuclear part is represented by chromohercynite with relics of chromepicotite; the edges - ferrochromium and chromemagnetite; locally observed thin rims of magnetite. Metasomatic substitutions in chromespinelides were accompanied by the addition of Fe (which replaced both di-and trivalent cations), Mn, Ni, and the removal of Mg, Al, Cr, and V. Rock transformations occurred in the high-temperature zone of the greenschist facies with reducing fluids at a relatively low fluid/rock ratio. The values of Cr# are ~0.5-0.7, Mg# ~0.4-0.6 for the cores which corresponds to the primary magmatic spinels composition area. Based on the composition of chromespinelides it is established the apohyperbasites are associated with the ophiolite’s association and close to ultramafic rocks of island-arc environments, including serpentinite diapires in the front parts of island arcs. A formational similarity is established – belonging to ophiolites, but there is a difference - in the P-T parameters of the conditions of metamorphic transformations when compared with serpentinites located to the north of the Dakhovsky shield