Modeling rhamnolipids production by Pseudomonas aeruginosa from immiscible carbon source in a batch system

A mathematical model to predict the rhamnolipids production by Pseudomonas aeruginosa from oleic acid in a two phase liquid-liquid batch reaction system, was developed in this study. The model was based on two theoretical assumptions: 1) the convective oleic acid mass transfer is coupled to a bioreaction in the aqueous liquid bulk, and 2) the volume of the immiscible oleic acid drops and the saturation concentration at the interface are a function of rhamnolipids production. The model was able to accurately predict the experimental growth of the Pseudomonas aeruginosa strain, and the rhamnolipids production data with oleic acid as carbon source. This mathematical approach indicated a high correspondence between the saturation dimensionless profiles of oleic acid at the interface and the experimental profiles of surface tension difference. This modeling approach may constitute a useful tool in the design and scaling-up of bioreactors applied to the production of biosurfactants with immiscible carbon sources.     

Investigation of the evolution of coronal bright points and magnetic field topology

Our investigation has been carried using the instruments onboard the Solar Dynamics Observatory (SDO) providing a high resolution of images (AIA photographs and HMI magnetograms). We have investigated the structure and magnetic evolution of several coronal bright points and small scale N-S polarity magnetic fluxes closely associated with them. We also compare the evolution of the magnetic polarities of elementary isolated sources of positive and negative fluxes (magnetic bipoles) and coronal bright points. Tiny (“elementary”) coronal bright points have been detected. A standard coronal bright point is shown to be a group of “elementary” coronal bright points that flare up sequentially. Our investigation shows that a change in the magnetic fluxes of opposite polarities is observed before the flare of a coronal bright point. We show that not all cases of the formation of coronal bright points are described by the magnetic reconnection model. This result has not been considered previously and has not been pointed out by other authors.     

Chemical composition of Russian Arctic precipitation in 2007-2015

The results of observations of the chemical composition of precipitation in the Russian Arctic in 2007-2015 are summarized including the data from NP-35 drifting ice station obtained in 2007-2008 in the framework of the joint program of Arctic and Antarctic Research Institute and Voeikov Main Geophysical Observatory. The qualitative and quantitative difference in the chemical composition of precipitation in the Atlantic, Siberian, and Pacific sectors of the Russian Arctic is revealed. It is found that the concentration of microelements (heavy metals) in precipitation at NP-35 ice station did not exceed 12% of total ions at the lowest mineralization. The comparative analysis is presented of the concentration of sulfate ions in precipitation in Norilsk and at NP-35 ice stations.     

The temple of apollo (Delphi) strengthens novel thermoluminescence dating method

The temple of Apollo in Delphi (Greece), built in 550 B.C., has been used to reconfirm a novel method of dating carved megalithic stone buildings using thermoluminescence (TL) (Liritzis, 1994). A calcitic (marble) sample was taken from the western side of the well-known inscribed polygonal wall, which constitutes the southern external support foundations of the temple. A partially bleached TL methodology was devised to determine first the ancient residual TL and then the correct archaeological dose. The obtained TL age of 420 ± 300 B.C. is compatible, within the margin of error, with the archaeological age. © 1997 John Wiley & Sons, Inc.     

The charge distribution on interstellar grains—The effect of induced charge

A calculation of the equilibrium charge acquired by interstellar grains is given, which takes account of polarization charges that are induced in a grain by incident ions and electrons.Both metal and dielectric grains are considered and photoionization of the latter grains by UV radiation is taken into account where necessary. It is found that the inclusion of the polarization charges in the calculation is only important in gas clouds where the mean charge on a grain is low (<1e); that is, for HI regions and dense molecular clouds. In such clouds, the effect of the polarization charges is to increase the amount of negative charge acquired by a grain. A discussion is given concerning the validity of the classical electrostatic theory employed in the paper for small grains of radius 10^–6 cm, and some astrophysical consequences of the modification of the grain charge by polarization effects are considered.     

Studying the Deep Structure of Elbrus Volcano by Microseismic Sounding

This paper presents results from a study of the deep structure of the Elbrus edifice and adjacent areas using geophysical techniques. We confirmed the existence of a shallow magma chamber, derived a more accurate location of the chamber in the host rocks and its characteristic dimensions, and compared new results with known studies. More accurate estimates have been obtained for the temperature at the top of the magma chamber and new evidence is adduced concerning the deep structure of the fluid magmatic systems in the Elbrus volcanic area.     

Marymia: an Archean, amphibolite facies-hosted, orogenic lode-gold deposit overprinted by Palaeoproterozoic orogenesis and base metal mineralisation, Western Australia

The Marymia gold deposit, comprising two orebodies, Keillor 1 and Keillor 2, is at the northern end of the Plutonic Well greenstone belt in the Marymia Inlier, in the southern Capricorn Orogen, just north of the Yilgarn craton. The Marymia Inlier is a discrete fault-bounded Archean gneiss-granitoid-greenstone domain surrounded by sedimentary basins that were formed and variably metamorphosed and deformed during several Palaeoproterozoic orogenic cycles. The greenstone sequence at Marymia is stratigraphically and geochemically similar to greenstone sequences in the Yilgarn craton, but was subjected to further deformation and metamorphism in the Palaeoproterozoic. Late Archean deformation (D1-D2) was ductile to brittle-ductile in style, whereas Palaeoproterozoic deformation was predominantly brittle. Equilibrium mineral assemblages indicate that peak amphibolite-facies metamorphism (540-575 °C, <3 kb) was overprinted by greenschist-facies metamorphism (300-360 °C). Petrographic textures indicate that prograde metamorphism was coeval with D1-D2, with peak metamorphism early to syn D2. Gold mineralisation at Marymia is hosted in metamorphosed tholeiitic basalts and banded iron formation. On a gross scale, the distribution of gold is controlled by D2 folds and shear zones. Lithological contacts with strong rheological or chemical contrasts provide local controls. Gold-related alteration comprises subtle millimetre- to centimetre-wide zones of silicification with variable amounts of quartz, hornblende, biotite, K-feldspar, plagioclase, calcite/siderite, scheelite, titanite, epidote, sulfide and telluride minerals. Quartz veins are generally narrow and discontinuous with low total volume of quartz. Gold is sited in the wall rock, at vein salvedges or within stringers of wall rock within veins. There are two distinct opaque-mineral assemblages: pyrite-pyrrhotite-chalcopyrite-galena and hessite-petzite-altaite-Bi-telluride-galena. Ore samples are variably enriched in Ag, Te, Pb, W, Cu, S and Fe reflecting heterogeneity of the ore mineralogy. Structural timing and temperature of formation of alteration and ore minerals support deposition of gold during late peak amphibolite-facies metamorphism from neutral to alkaline (pH=5-6), moderately oxidising (log P_O2,-21-22) and CO₂-bearing (X_CO2 Ƹ.2) fluids. The total sulfur content of the fluid is estimated at 1mDS. Lead isotope compositions support derivation of lead from within the local greenstone sequence. Gold lodes were deformed by faults and shear zones in the Palaeoproterozoic, with only limited remobilisation. Subeconomic, carbonate vein- and breccia-hosted base metal mineralisation is locally hosted within Palaeoproterozoic fault zones, which clearly cut gold lodes. Base-metal-related alteration is characterised by intense carbonatisation, chloritisation, and albitisation of the mafic host rocks. Mineral assemblages are consistent with formation at greenschist facies conditions. Lead isotope compositions support crystallisation at ca. 1.7 Ga from lead that is similar in composition to earlier gold-related galena.     

Electrical and electromagnetic surveys to locate possible causes of water seepage to ground surface at a quarry open pit near Helwan city,Egypt

Water seepage to ground surface at a limestone quarry located at Wadi Garawy about 20 km south-east of Helwan city in Egypt posed a real threat to the mining activity at the quarry. The quarry area is known to be very dry for decades and away from water utilities and infrastructures that may cause water leaks to the quarry. Geophysical investigation including 1D Vertical Electrical Sounding (VES), 2D Electrical Resistivity Tomography (ERT) and 1D Transient Electromagnetic (TEM) surveys were conducted to characterize the rock sequence and locate what could be a possible source of water seepage to the quarry. The resistivity profiles generated from the VES and TEM surveys mapped the rock units in the area down to depths exceeded 100 m. The ERT profiles acquired from the quarrying zone close to the water seepage spot have imaged the top of groundwater level at few meters below the ground surface at the quarry open pit. The spot of groundwater seepage seemed to occur at an area of limestone dissolution that were filled by finer sediments. The finer sediments acted as a hydrological conduit that allowed an upward seepage of groundwater to ground surface under the capillary action effect.