Site occupancies in synthetic monoclinic amphiboles: Rietveld structure refinement and infrared spectroscopy of (nickel, magnesium, cobalt)-richterite.

Amphiboles were synthesized at 750 8C, 1 kbar (H2O) on the binary joins (nickel, magnesium)-richterite and (magnesium, cobalt)-richterite. Structural variations and site occupancies were characterized by Rietveld structure refinement, with final RBragg indices in the range 4–9%, and by powder infrared spectroscopy in the principal OH-stretching region. Site-occupancy refinement of Ni-Mg and Mg-Co distributions give the partition coefficients over M1,3 and M2 where KM21 5 (M21/Mg)M1,3/(M21/Mg)M2, and M21 5 Ni21 or Co21, K 5 2.98 6 0.37 and K 5 1.34 6 0.31. Both Kd Ni Co values are greater than 1.0, d d whereas [6]r(Ni21 ) , [6]r(Mg) , [6]r(Co21 ); this indicates that cation size is not the primary factor affecting the ordering of Ni-Mg and Mg-Co over the octahedral sites. The infrared spectra of intermediate binary compositions show fine structure caused by ordering of Ni- Mg or Mg-Co over the M1,3 sites and by ordering of Na and M (vacancy) at the A site; thus intermediate compositions show an eight-band spectrum in the principal OHstretching region. Precise band intensities were derived by nonlinear least-squares fitting of Gaussian band shapes to the observed spectra. The relative observed intensities of the combinations of bands 3IA1 2IB1 IC and IB 1 2IC 1 3ID are in accord with the equations o o o o o o of Burns and Strens (1966), indicating that there is no significant variation in molar absorptivity with frequency (energy) for individual bands within a single sample (spectrum). Combined with the results of Skogby and Rossman (1991) on polarized single-crystal infrared spectra of amphiboles, this result suggests that different local configurations of M1,3 cations in amphiboles couple such that the transition probabilities of the associated OH groups are equal

Offsetting of CO₂ emissions by air capture in mine tailings at the Mount Keith Nickel Mine, Western Australia: Rates, controls and prospects for carbon neutral mining

The hydrated Mg-carbonate mineral, hydromagnesite [Mg₅(CO₃)₄(OH)₂•4H₂O], precipitates within mine tailings at the Mount Keith Nickel Mine, Western Australia as a direct result of mining operations. We have used quantitative mineralogical data and δ¹³C, δ¹⁸O and F¹⁴C isotopic data to quantify the amount of CO₂fixation and identify carbon sources. Our radiocarbon results indicate that at least 80% of carbon stored in hydromagnesite has been captured from the modern atmosphere. Stable isotopic results indicate that dissolution of atmospheric CO₂ into mine tailings water is kinetically limited, which suggests that the current rate of carbon mineralization could be accelerated. Reactive transport modeling is used to describe the observed variation in tailings mineralogy and to estimate rates of CO₂ fixation. Based on our assessment, approximately 39,800 t/yr of atmospheric CO₂ are being trapped and stored in tailings at Mount Keith. This represents an offsetting of approximately 11% of the mine's annual greenhouse gas emissions. Thus, passive sequestration via enhanced weathering of mineral waste can capture and store a significant amount of CO₂. Recommendations are made for changes to tailings management and ore processing practices that have potential to accelerate carbonation of tailings and further reduce or completely offset the net greenhouse gas emissions at Mount Keith and many other mines

Overview of studies on the antimicrobial effect of plant additives in vitro and in raw minced pork products

Saabunud / Received 15.09.2022 ; Aktsepteeritud / Accepted 17.06.2023 ; Avaldatud veebis / Published online 15.08.2023 ; Vastutav autor / Corresponding author Kadrin Meremäe ; [email protected] additives can be used in food technologies as natural additives to replace synthetic food additives partially or completely. The present work aims to give an overview of studies that have been carried out over the years 2011–2019 in the Department of Food Hygiene and Safety at the Estonian University of Life Sciences on the antimicrobial activity of plant additives in vitro as well as in raw minced pork products in the perspective to find effective candidates to use them further in meat products. The findings of the in vitro studies showed that the strongest bacterial growth inhibition was observed in the 96% ethanol extracts of rhubarb root and petiole as well as berries of blackcurrant and chokeberry. In the present in vitro study, plant extracts had the strongest antimicrobial activity against Campylobacter jejuni. In raw minced pork studies, the total microbes as well as yeasts and molds were inhibited in raw minced pork samples only in the presence of powders of rhubarb petioles and tomato or their mixture. In conclusion, this work revealed that powders of rhubarb, tomato and berries of blackcurrant and chokeberry are perspective candidates for inhibiting microbial growth in raw minced pork products.Uuringuid on finantseerinud: • Eesti Teadusagentuur (PRG1441) “Looduslike bio- aktiivsete ainete toimete mehhanismide uurimine loomsetes toitudes”, • projekt P180279VLTR “Looduslike bioaktiivsete ainete toime ning seonduvate mehhanismide uuri- mine toidumaatriksites”, • projekt P170054VLTH “Toidutaimede metabo- loomika ning sekundaarsete metaboliitide antioksü- dantse ja antibakteriaalse toime intensiivsuse ja mehhanismide uurimine”, • projekt 8-2/T15024VLTH “Säästvad taimsed lisan- did tervislikumate lihatoodete saamiseks – ideede tõestamine”. We would like to express thank to the Estonian Research Council (Project No PRG1441), the Estonian University of Life Sciences (Projects No P180279VLTR and P170054VLTH) and Ministry of Agriculture (Project No 8-2/T15024VLTH).Uuringuid on finantseerinud: • Eesti Teadusagentuur (PRG1441) “Looduslike bio- aktiivsete ainete toimete mehhanismide uurimine loomsetes toitudes”, • projekt P180279VLTR “Looduslike bioaktiivsete ainete toime ning seonduvate mehhanismide uuri- mine toidumaatriksites”, • projekt P170054VLTH “Toidutaimede metabo- loomika ning sekundaarsete metaboliitide antioksü- dantse ja antibakteriaalse toime intensiivsuse ja mehhanismide uurimine”, • projekt 8-2/T15024VLTH “Säästvad taimsed lisan- did tervislikumate lihatoodete saamiseks – ideede tõestamine”. We would like to express thank to the Estonian Research Council (Project No PRG1441), the Estonian University of Life Sciences (Projects No P180279VLTR and P170054VLTH) and Ministry of Agriculture (Project No 8-2/T15024VLTH)

Screening for new natural food additives with antibacterial properties against pathogenic bacteria : [poster]

• Due to increasing customer awareness, there is a trend to seek new natural food additives that can be used as antibacterial and/or antioxidative agents in food products [1] • Plant-based extracts consist of compounds that can possess antibacterial properties and may extend the shelf-life and enhance food safety [2] Aim: Find potential natural antimicrobials for food industry by testing antimicrobial properties of plant extracts against pathogenic bacteria.Poster of the Nordic Natural Products Conference 2023.This work was supported by the Estonian Research Council grant PRG 1441.This work was supported by the Estonian Research Council grant PRG 1441

Encapsulated Single Crystal Growth and Annealing of the High-Temperature Superconductor Tl-2201

Highly-perfect platelet single crystals of Tl_2Ba_2CuO_{6+d} (Tl-2201) were grown by a self-flux technique. A novel encapsulation scheme allowed the precursors to react prior to the sealing required to contain volatile thallium oxides, and permitted the removal of melt at the conclusion of growth, reproducibly producing high yields of clean crystals. The crystals were annealed under well-controlled oxygen partial pressures, then characterised. They have sharp superconducting transitions, narrow X-ray rocking curves and a low 4% substitution of thallium by copper, all evidence of their high perfection and homogeneity. The crystals are orthorhombic at most dopings, and a previously unreported commensurate superlattice distortion is observed.Comment: 8 pages, 5 figures, submitted to Journal of Crystal Growt

The crystal structure of stichtite, re-examination of barbertonite, and the nature of polytypism in MgCr hydrotalcites

abStraCt Stichtite, ideally Mg 6 Cr 2 CO 3 (OH) 16 •4H 2 O, from Stichtite Hill, Tasmania, Australia, and barbertonite, also ideally Mg 6 Cr 2 CO 3 (OH) 16 •4H 2 O, from the Kaapsehoop asbestos mine, South Africa, have been studied by powder X-ray diffraction and their structures have been refined using the Rietveld method. Stichtite from Stichtite Hill crystallizes in the rhombohedral space group R3m, with unitcell parameters a = 3.09575(3) and c = 23.5069(6) Å, V = 195.099(6) Å 3 , with Z = 3/8. Barbertonite from the Kaapsehoop asbestos mine crystallizes in the hexagonal space group P6 3 /mmc. The co-type specimens of barbertonite were found to be intergrown mixtures consisting of barbertonite and stichtite. Unit-cell parameters of barbertonite from the co-type specimens were a = 3.09689(6), c = 15.6193(8) Å, and V = 129.731(8) Å 3 and a = 3.09646(6), c = 15.627(1) Å V = 129.76(1) Å 3 , and Z = ¼. Rietveld refinements of both stichtite and barbertonite show that they are polytypes rather than polymorphs and do not represent distinct mineral species. Several possible nomenclature systems are discussed for the naming of hydrotalcite minerals and groups. Raman band assignments are also presented for stichtite from Stichtite Hill. Stichtite and hydrotalcite minerals make up a large proportion of the ore at the Mount Keith nickel mine in Western Australia. Bulk powder diffraction shows the ore contains 6.1 wt% stichtite and 5.6 wt% iowaite. Hydrotalcite group minerals provide an important potential reservoir of CO 2 . At Mount Keith, the amount of CO 2 mined as stichtite could exceed 45 000 metric tons per year, while exchange of Cl for CO 3 could fix in excess of 40 000 metric tons CO 2 per year if end-member iowaite is reacted to form pyaroaurite

Colloidal Nanoparticles of Ln3+-Doped LaVO4: Energy Transfer to Visible- and Near-Infrared-Emitting Lanthanide Ions

Colloidal, organic solvent-soluble Ln3+-doped LaVO4 nanoparticles have been synthesized by a precipitation reaction in the presence of (C18H37O)2PS2- as ligand, that coordinates to the surface of the nanoparticles. The materials are well soluble in chlorinated solvent such as chloroform. Energy transfer of excited vanadate groups has been observed for Ln3+ ions that emit in the visible and the near-infrared (Eu3+, Tm3+, Nd3+, Er3+, Ho3+, Dy3+, Sm3+, Pr3+), thus making it a very generic sensitization mechanism. The LaVO4 nanoparticles have a different crystal structure than bulk LaVO4 ones (xenotime instead of monazite), similar to YVO4 nanoparticles. This xenotime crystal structure results in a more asymmetric crystal field around the Ln3+ ions that is advantageous to their luminescence, for it increases the radiative rate constant, thus reducing quenching processes

The crystal structure of Ga-rich plumbogummite from Tsumeb, Namibia

Ga-rich plumbogummite, (Pb0.87,Ca0.13)Σ1.00H(Al1.95,Ga1.05)Σ3.00(PO4)2(OH)6, from Tsumeb, Namibia, has rhombohedral symmetry, space group R3m, with the cell parameters a = 7.0752(19) Å, c = 16.818(4) Å and V = 729.1(3) Å3. The crystal structure has

Revised values of the bond valence parameters for [6] Sb(v)-O and [3-11] SB(III)-O

Bond valence parameters r0 and b have been re-determined for [3-11]Sb(III)-O and [6]Sb(V)-O, utilising crystal structures of natural and inorganic compounds from the Inorganic Crystal Structure Database. Bond valence parameters for Sb(III) were obtained from a best-fit r0-b curve for 242 independent SbOn polyhedra. For [6]Sb(V), a curve of best fitting r0-b pairs was determined by fitting to 207 independent SbO6 octahedra; b was then determined by optimising bond valence sums on the oxygens of Sb 2O5 and Sb2O4, given the limited, low quality structural data available for Sb(V) coordination numbers other than 6. Parameter values that minimised r.m.s. deviation from the ideal bond valence sums were r0 = 1.925 Å; and b= 0.455 Å; for Sb(III) and r0=1.904 Å;, b = 0.430 Å; for [6]Sb(V). The increase in r0 for Sb(III) may represent the repulsive effect of the lone-pair electrons, while the difference in b indicates higher polarisability when these electrons are present. Consideration of subsets of data for differing coordination numbers demonstrates that Sb(III) parameters are applicable to all SbOn coordination numbers (CN = 3-11). We also show that the apparent overbonding using the classical b value cannot be an artefact of unresolved site splitting. For Sb(V), independent determination of b allows bond lengths cautiously to be estimated for CN ≠ 6. This work confirms that the "universal" value b = 0.37 Å; is not adequate for heavier cations such as Sb