Minerálne zloženie kryštalických vápencov z lokality Dobšiná - Kruhová (Slovenská republika)

Crystalline limestones containing fragments of amphibolites from the locality Dobšiná - Kruhová are part of the Klátov complex (Northern Gemericum, Western Carpathians). The colour of studied rocks is light grey with massive texture and granoblastic structure. Inhomogeneous mottled to breccia-like character of a crystalline limestones is caused by the presence of amphiboles in the studied rocks. The identified mineral association of crystalline limestones consists of calcite, amphiboles (pargasite, magnesio-hornblende, actinolite), clinopyroxenes (diopside), albite and titanite. Chemical zonation of amphiboles from the crystalline limestones and fragments of amphibolites have been studied in BSE imaging. Light grey BSE zone is represented by pargasite (with more Fe2+ up to 1.37 apfu and less Mg up to 2.26 apfu) and dark grey BSE zone is represented by magnesio-hornblend and actinolite (less Fe2+ 0.68 apfu in magnesio-hornblende; 0.62 apfu in actinolite and more Mg up to 3.30 apfu in magnesio-hornblende and up to 4.03 apfu in actinolite). Diopside has slightly higher content of Al (up to 0.13 apfu) and low content of Fe2+ (up to 0.17 apfu) with XMg ratio in the range 0.83 - 0.96. Chemical composition of albites is Ab91.12-98.21An1.52-5.12 with ortoclase component in the range 0.22 - 4.49 mol. %. Titanites from the amphibolite fragments and crystalline limestones have identical chemical composition (Ca up do 1.00 apfu, Si up to 0.97 apfu). Lower content of Ti (0.88 - 0.95 apfu) and higher content of F (up to 0.27 wt. %) and H2O (up to 0.38 wt. %) is present. In titanites not very significant (Al, Fe3+) + (OH, F) ↔ Ti + O substitution was also identified. We assume that pargasite and magnesio-hornblende are products of prograde etape of metamorphosis unlike actinolite which is product of retrograde etape of metamorphosis. Diopside was generated by dehydration and decomposition processes of magnesio-hornblende and pargasite in a high-temperature prograde regime of metamorphosis in the conditions of upper amphibolite facies. Calcite is chemically pure, presence of dolomite has not been confirmed.

Incommensurately Modulated Crystal Structure and Photoluminescence Properties of Eu2O3- and P2O5-Doped Ca2SiO4 Phosphor

We prepared four types of Eu2O3- and P2O5-doped Ca2SiO4 phosphors with different phase compositions but identical chemical composition, the chemical formula of which was (Ca1.950Eu3+0.013☐0.037)(Si0.940P0.060)O4 (☐ denotes vacancies in Ca sites). One of the phosphors was composed exclusively of the incommensurate (IC) phase with superspace group Pnma(0β0)00s and basic unit-cell dimensions of a = 0.68004(2) nm, b = 0.54481(2) nm, and c = 0.93956(3) nm (Z = 4). The crystal structure was made up of four types of β-Ca2SiO4-related layers with an interlayer. The incommensurate modulation with wavelength of 4.110 × b was induced by the long-range stacking order of these layers. When increasing the relative amount of the IC-phase with respect to the coexisting β-phase, the red light emission intensity, under excitation at 394 nm, steadily decreased to reach the minimum, at which the specimen was composed exclusively of the IC-phase. The coordination environments of Eu3+ ion in the crystal structures of β- and IC-phases might be closely related to the photoluminescence intensities of the phosphors.

Factors of strength increasing of metals produced by selective laser melting of powders

Standard samples of metal powders of various chemical composition were made for mechanical tests by selective laser melting. The paper describes an increase in strength characteristics of all samples made by melting comparing with similar parameters of monolithic samples of identical chemical composition. It is established that ultrafine-grained structure and condensation of nanoparticles could be cosidered factors of strength increase.

Ag2S2O8 meets AgSO4: the second example of metal–ligand redox isomerism among inorganic systems

Ag(i)2S2O8 – prepared here for the first time – constitutes a redox isomer of the already known Ag(ii)SO4. These “electromers” have identical chemical composition but they differ in all important physicochemical properties.

Thoughts on the “missing link” between saltworks biology and solat salt quality

Although solar salterns worldwide use seawater of identical chemical composition as the raw material for salt production, the size and quality of the halite crystals that precipitate in the crystallizer ponds is highly variable. Biological processes have been implicated to be responsible for the differences observed, but the “missing link” between saltworks biology and solar salt quality has never unequivocally been identified. This paper presents an overview of the different organic chemicals that are formed by the members of the microbial communities in saltern evaporation and crystallizer ponds as osmotic stabilizers as well as different compounds formed during further microbial metabolism of those osmotic solutes. Examination of the in situ concentrations and the possible role of glycerol, glycine betaine, ectoine, dihydroxyacetone, acetate, lactate, and other organic compounds failed to identify one or more compounds that may accumulate at concentrations high enough to significantly modify the formation of sodium chloride crystals in the salterns and to negatively influence the quality of the salt produced.

Growth of Eutectic Austenite in Free Graphite Cast Irons

The present work investigates the growth of the eutectic austenite of hypereutectic free graphite cast irons of different graphite morphology. The study was based on the analysis of several samples obtained from a highly hypereutectic cast iron melt. A hypereutectic melt was used in order to ensure the absence of proeutectic austenite. With the aim of obtaining samples of different graphite morphology but nearly identical chemical composition, the melt was nodularized by using a standard procedure, and different samples were cast after various fading periods. Through this procedure, spheroidal, vermicular and flake graphite samples were obtained The results show that the eutectic austenite grows dendritically in all samples investigated. Nevertheless, significant differences were found in the size of the solidification units (grains) and in the microsegregation patterns as the graphite morphology changes from spheroidal to flake.

The S-Layer Proteins of Two Bacillus stearothermophilus Wild-Type Strains Are Bound via Their N-Terminal Region to a Secondary Cell Wall Polymer of Identical Chemical Composition

ABSTRACT Two Bacillus stearothermophilus wild-type strains were investigated regarding a common recognition and binding mechanism between the S-layer protein and the underlying cell envelope layer. The S-layer protein from B. stearothermophilusPV72/p6 has a molecular weight of 130,000 and assembles into a hexagonally ordered lattice. The S-layer from B. stearothermophilus ATCC 12980 shows oblique lattice symmetry and is composed of subunits with a molecular weight of 122,000. Immunoblotting, peptide mapping, N-terminal sequencing of the whole S-layer protein from B. stearothermophilus ATCC 12980 and of proteolytic cleavage fragments, and comparison with the S-layer protein from B. stearothermophilus PV72/p6 revealed that the two S-layer proteins have identical N-terminal regions but no other extended structurally homologous domains. In contrast to the heterogeneity observed for the S-layer proteins, the secondary cell wall polymer isolated from peptidoglycan-containing sacculi of the different strains showed identical chemical compositions and comparable molecular weights. The S-layer proteins could bind and recrystallize into the appropriate lattice type on native peptidoglycan-containing sacculi from both organisms but not on those extracted with hydrofluoric acid, leading to peptidoglycan of the A1γ chemotype. Affinity studies showed that only proteolytic cleavage fragments possessing the complete N terminus of the mature S-layer proteins recognized native peptidoglycan-containing sacculi as binding sites or could associate with the isolated secondary cell wall polymer, while proteolytic cleavage fragments missing the N-terminal region remained unbound. From the results obtained in this study, it can be concluded that S-layer proteins from B. stearothermophilus wild-type strains possess an identical N-terminal region which is responsible for anchoring the S-layer subunits to a secondary cell wall polymer of identical chemical composition.