Optical Activity of Metal Nanoclusters Deposited on Regular and Doped Oxide Supports from First-Principles Simulations

We report a computational study and analysis of the optical absorption processes of Ag20 and Au20 clusters deposited on the magnesium oxide (100) facet, both regular and including point defects. Ag20 and Au20 are taken as models of metal nanoparticles and their plasmonic response, MgO as a model of a simple oxide support. We consider oxide defects both on the oxygen anion framework (i.e., a neutral oxygen vacancy) and in the magnesium cation framework (i.e., replacing Mg++ with a transition metal: Cu++ or Co++). We relax the clusters’ geometries via Density-Functional Theory (DFT) and calculate the photo-absorption spectra via Time-Dependent DFT (TDDFT) simulations on the relaxed geometries. We find that the substrate/cluster interaction induces a broadening and a red-shift of the excited states of the clusters, phenomena that are enhanced by the presence of an oxygen vacancy and its localized excitations. The presence of a transition-metal dopant does not qualitatively affect the spectral profile. However, when it lies next to an oxygen vacancy for Ag20, it can strongly enhance the component of the cluster excitations perpendicular to the surface, thus favoring charge injection.

Impact of Cement Dust on Physical and Chemical Nutrients Properties of Forest Topsoil

: The study examined the impact of Cement dust on physical and chemical nutrients properties of forest topsoil in close proximity to a major private cement industry in Obajana, Kogi State, Nigeria using standard methods by collecting Topsoil samples for physical and chemical properties analyses which are particle size, moisture content, pH, carbon, nitrogen,phosphorus, potassium, sodium, calcium, magnesium, cation exchange capacity and organic matter.Data revealed a strong influence of the particulate pollutants on the forest topsoil in close proximity to the Cement factory. It was observed that the soil properties; moisture content and soil pH varied at distances away from the factory. The result showed that the Cement dust particles entering the soil increased the pH of the soil, it more alkaline. The highest pH (6.03) was observed from hundred and fifty meters sample indicating the highest particulate pollution. There were also variations in the other soil nutrient properties; carbon, nitrogen, phosphorus, potassium, sodium, calcium, magnesium, cation exchange capacity and organic matter arising from the effect of cement dust. High organic matter content was recorded in the location samples compared with the control sample. This is attributed to the addition of cement dust to the soils, resulting in improved organic-matter cycling and plant growth. The result also showed that the chemical properties; organic carbon (OC), organic matter (OM), phosphorus (P), potassium (K), sodium (Na), calcium (Ca) and magnesium (Mg) are significantly higher in the study areas than the control. The study therefore concludes that the emission of cement dust on the forest stands over the years was found to have significantly affected the topsoil properties.

The crystal structure, morphology and mechanical properties of diaquabis(omeprazolate)magnesium dihydrate

The crystal structure of diaquabis(omeprazolate)magnesium dihydrate (DABOMD) in the solid state has been determined using single-crystal X-ray diffraction. Single crystals of DABOMD were obtained by slow crystallization in ethanol with water used as an antisolvent. The crystal structure shows a dihydrated salt comprising a magnesium cation coordinating two omeprazolate anions and two water molecules (W1) that are strongly bound to magnesium. In addition, two further water molecules (W2) are more weakly hydrogen-bonded to the pyridine nitrogen atom of each omeprazolate anion. The crystal structure was utilized to estimate key material properties for DABOMD, including crystal habit and mechanical properties, which are required for improved understanding and prediction of the behaviour of particles during pharmaceutical processing such as milling. The results from the material properties calculations indicate that DABOMD exhibits a hexagonal morphology and consists of a flat slip plane through the (100) face. It can be classed as a soft material based on elastic constant calculation and exhibits a two-dimensional hydrogen-bonding framework. Based on the crystal structure, habit and mechanical properties, it is anticipated that DABOMD will experience large disorder accompanied by plastic deformation during milling.

Assessment of Physical and Chemical Stability of Different Magnesium Compounds in Tablets

Modern lifestyle, excessive chemicalization of agricultural products, excessive processing and refining of food, cause a decrease in daily intake of magnesium, cation with an extremely important role in prevention and treatment of many diseases. As a result, there arises the need for extra magnesium intake in the form of dietary supplements. In this study were evaluated the physical and chemical stability of magnesium-containing tablets, depending on the active compound and the excipients used. Magnesium tablets in the form of orotate, lactate, citrate, oxide and hydroxide were taken into study and physical and chemical stability were observed over the validity period, at 6 and at 12 months after expiry date. There were no changes in physical and chemical stability during the validity period of the studied tablets. At 6 months after the expiry date, were observed variations in chemical composition with decrease in magnesium concentration to 98% of the declared value, only in the case of tablets containing magnesium lactate. At 12 months, the magnesium concentration decreased in all analysed samples, with no statistically significant differences (p[0.05) between the types of magnesium compounds � 95% for the orotate, 93% for the lactate, 90% for the oxide and hydroxide, respectively 85% for citrate. The results of this study indicate the therapeutically safety for using these tablets 6 months after the expiry date.

Influence of the Compensating Cation Nature on the Water Adsorption Properties of Zeolites

The influence of the compensating cation (Na+, Li+, Mg2+) nature on the water adsorption properties of LTA and FAU-type zeolites was investigated. Cation exchanges were performed at 80 °C for 2 h using 1 M aqueous solutions of lithium chloride (LiCl) or magnesium chloride (MgCl2). XRF and ICP-OES analyses indicate that the cation exchange yields reach values between 59 to 89% depending on the number of exchange cycles and the nature of the zeolite and cation, while both zeolites structures are preserved during the process, as shown by XRD and solid state NMR analyses. Nitrogen adsorption-desorption experiments indicate a higher available microporous volume when sodium cations are replaced by smaller monovalent lithium cations or by divalent magnesium cations because twice less cations are needed compared to monovalent cations. Up to 15% of gain in the available microporous volume is obtained for FAU-type zeolites exchanged with magnesium cation. This improvement facilitates the adsorption of water with an increase in the water uptake up to 30% for the LTA and FAU type zeolites exchanged with magnesium. These exchanged zeolites are promising for uses in water decontamination because a smaller amount is needed to trap the same amount of water compared to their sodium counterparts.

Investigation of Grignard Reagent as an Advanced Base for Aza-Claisen Rearrangement

Employing iPrMgCl as an advanced base instead of lithium hexamethyldisilazane (LHMDS) resulted in dramatic improvements in aza-Claisen rearrangement. This advance is considered responsible for the increased bulkiness of the alkoxide moiety (including magnesium cation and ligands), followed by a resultant conformational change of the transition state. To support this hypothesis, various substrates of aza-Claisen rearrangement were prepared and screened. In addition, a molecular dynamic simulation study was performed to investigate and compare the structural stability of reaction intermediates.

Mg2+ homeostasis and transport in cyanobacteria – at the crossroads of bacterial and chloroplast Mg2+ import

Magnesium cation (Mg2+) is the most abundant divalent cation in living cells, where it is required for various intracellular functions. In chloroplasts and cyanobacteria, established photosynthetic model systems, Mg2+is the central ion in chlorophylls, and Mg2+flux across the thylakoid membrane is required for counterbalancing the light-induced generation of a ΔpH across the thylakoid membrane. Yet, not much is known about Mg2+homoeostasis, transport and distribution within cyanobacteria. However, Mg2+transport across membranes has been studied in non-photosynthetic bacteria, and first observations and findings are reported for chloroplasts. Cyanobacterial cytoplasmic membranes appear to contain the well-characterized Mg2+channels CorA and/or MgtE, which both facilitate transmembrane Mg2+flux down the electrochemical gradient. Both Mg2+channels are typical for non-photosynthetic bacteria. Furthermore, Mg2+transporters of the MgtA/B family are also present in the cytoplasmic membrane to mediate active Mg2+import into the bacterial cell. While the cytoplasmic membrane of cyanobacteria resembles a ‘classical’ bacterial membrane, essentially nothing is known about Mg2+channels and/or transporters in thylakoid membranes of cyanobacteria or chloroplasts. As discussed here, at least one Mg2+channelling protein must be localized within thylakoid membranes. Thus, either one of the ‘typical’ bacterial Mg2+channels has a dual localization in the cytoplasmic plus the thylakoid membrane, or another, yet unidentified channel is present in cyanobacterial thylakoid membranes.

Recovery of degraded area of Urochloa decumbens with turkey litter fertilizer

The aimed of this study was to evaluate the effects of different dosages of turkey litter on soil’s chemical attributes and yield of the Urochloa decumbens in classified as degraded pasture. The work was performed at the municipality of Mineiros-GO between October/2011 and September/2013 in Quartzipsamment soil. The treatments consisted in applications of 0, 3, 6, 9 and 12 Mg ha-1 of turkey litter at a randomized-complete blocks design with four replications. Was evaluated the fodder’s productivity and the following soil’s chemical attributes: organic matter, hydrogenionic potential (CaCl2), phosphorus (resin), potassium, calcium, magnesium, cation exchange capacity and base saturation of soil. In general terms, the increase of turkey litter’s doses increased the grass productivity and the supply of nutrients of the soil, maintaining the balance of the soil-plant system. The dosage of 12 Mg ha-1 year-1 of turkey litter ensure higher amounts in the soil’s chemical attributes and in the productivity of dry mass of Urochloa decumbens.

Promising Directions for the Stabilization of Ferroalloy Production Slags

In this paper the analysis of the processes for spontaneous decay of slags from the production of refined ferroalloy grades is performed. It is shown that the main reason for the decay is the formation of a dicalcium silicate in highly basic melts with CaO / SiO2 ratio of 1.5-3.1. Based on the performed studies, three main promising directions for the stabilization of slags of ferroalloy production have been formed. First direction is the replacement of the calcium cation (or transformation) in a dicalcium silicate, for example, with the magnesium cation or the production of non-decaying compounds of the gehlenite type (2CaO·Al2O3·SiO2), mainly due to the application of phase composition peculiarities of the waste rock for ferroalloy raw materials. Second direction is the reduction of the dicalcium silicate content with a decrease in the ratio of CaO / SiO2 in the slag less than 1.4, due to the separation of the silicothermic reduction process into two stages, obtaining in the first stage a low-basic (CaO / SiO2 = 1.3-1.4) non-decaying tailing slag, and on the second one - highly basic return slag (1.8-1.9), which is used in the first stage of this technological chain. The third direction is the replacement of the SiO anion of dicalcium silicate with other anions, for example, ВО by means of small additions of calcium borate, colemanite, etc. A possibility for stabilization of ferroalloy production slags with obtaining of construction crushed stone corresponding to the requirements of TU 0798-69-00186499-2014 "Crushed stone and sand from ferroalloy slags. Technical conditions», is shown experimentally.