Chemical solubility of phosphate glasses in the system Na2O-CaO-MgO-P2O5-Al2O3-TiO2 in aqueous solutions of different pH values

Phosphate glasses of different composition ranges show very different solubility behaviour in aqueous solutions of pH 4 and 5.8. With inereasing P2O5 concentrations between 38 and 52 mol% , in the system Na2O-CaO-MgO-P2O5-Al2O3-TiO2 , the dissolution rate generally increases, however, the most notable increase is observed at P2O5 concentrations larger than 48 mol%. Additives of TiO2 and AI2O3 increase the stability to corrosion. Glasses with compositions in the metaphosphate range show larger dissolution rates in slightly acidic medium than glasses near the invert glass range. Glasses in the invert glass range show a stronger increase in the dissolution rates with decreasing pH value and also deceleration of the dissolution with time

Crystallization and vicosity of phosphate melts in the system Na2O-CaO-MgO-P2O5-Al2O3-TiO2

Glasses in the system Na2O-CaO-MgO-P2O5-Al2O3-TiO2 were studied with respeet to their crystallization and viscosity. Glasses in the metaphosphate range are composed of phosphate chains, and possess a comparably small tendeney to crystallization. Here, AlPO4 in a cristobalite-like modification and Ca2P2O7 are formed. Glasses in the intermediate range between metaphosphate and invert glass structures are composed of smaller phosphate units and show higher erystal growth velocities as well as higher viscosities. Additions of MgO, AI2O3 and TiO2 result in a strengthening of the glass network, and hence, inereasing viscosities and a notably smaller tendeney to crystallization

4MOST : the 4-metre multi-object spectroscopic telescope project in the assembly, integration, and test phase

4MOST is a new high-multiplex, wide-field spectroscopic survey facility under construction for ESO's 4m-VISTA telescope at Paranal, Chile. Its key specifications are: a large field of view of 4.4 square degrees, a high multiplex fibre positioner based on the tilting spine principle that positions 2436 science fibres in the focal surface of which 1624 fibres go to two low-resolution optical spectrographs (R = λ/Δλ ~ 6500) and 812 fibres transfer light to the high-resolution optical spectrograph (R ~ 20,000). Currently, almost all subsystems are completed and full testing in Europe will be finished in spring 2023, after which 4MOST will be shipped to Chile. An overview is given of instrument construction and capabilities, the planned science of the consortium and the recently selected community programmes, and the unique operational scheme of 4MOST

Model of the carbon concentrating mechanism in chloroplasts of eukaryotic algae

A generic chloroplast-based model for the carbon concentratingmechanism (CCM) in eukaryotic algae is presented. The finestructure of chloroplasts is represented by separate compartments:marginal and bulk stroma, pyrenoid, girdle lamella, bulk thylakoids,and central lamella traversing the pyrenoid. The roles of theindividual structural elements of the chloroplast with respect tothe CCM and the effect of carbonic anhydrase activity in variouscompartments are analyzed. Hypothetical HCO3- transport into theacidic thylakoid lumen is adjusted by imposing an optimizationprinciple: a given CO2 at the site of Rubisco is achievedwith minimum energy costs for the CCM. Our model is highlyefficient in terms of saturation of Rubisco carboxylase activityand the affinity of the chloroplast for CO2, if either a girdlelamella or a pyrenoid is present. The highest efficiency isachieved with a pyrenoid. A eukaryotic CCM is not necessarilyassociated with accumulation of dissolved inorganic carbon (DIC)as in cyanobacteria.Chloroplasts are categorized into four types corresponding tomorphological characteristics of all major algal classes with regardto the presence of pyrenoids, girdle lamellae, and the distributionof CA activity