Oxygen hole-doping effects on a spin-chain system, Ca[subscript 2+chi]Y[2-chi]Cu₅O[subscript 10-delta](CaYCuO) are reported. CaYCuO is a good specimen to study the magnetic properties of the CuO₂ chain at the ground state because it has no complex structure other than the chain and it has hole dopability up to the formal copper valence number of +2.4. Specifically, we can dope holes into the CuO₂ chain by substituting Ca²⁺ for Y³⁺ or by utilizing oxygen deficiency. After a systematic study of the two methods to dope holes, we found that oxygen doping makes a more critical change in magnetic ordering in the chain than the replacement of Ca²⁺. Oxygen deficiency effects of the chain on the magnetic properties were explained using a mean field theory. A new relation for the effective hole doping was found as p = x - [alpha delta], where a = 3/2(x - [delta]) - 1/4. We study the anisotropy of magnetic properties of single crystal Li-cathode material (LiFePO₄) for g-factor, Curie-Weiss temperature, and effective moment. Magnetic properties Au/SiO₂ coated [gamma]-Fe₂O₃ are compared with pure [gamma]-Fe₂O₃ finding a decrease in the blocking temperature and the irreversible temperature for the coated nanoparticles. / text

The objectives of this study were two-fold: firstly to add to existing knowledge about the reaction of peracid with both iodide and sulfides in the presence of micelles (anionic and non-ionic) and α-cyclodextrin. The reaction between iodide and peracid had previously been studied only at 25°C in non-ionic, anionic micellar and alpha cyclodextrin; while the reaction of sulfides and peracid had only been investigated in the presence of α-cyclodextrin at one temperature. This study has investigated the previously undetermined effect of temperature on these reactions and how changes in temperature can affect the process of reactants binding to the micelle or cyclodextrin catalyst. The second objective was to obtain quantitative information about reactivity in ordered aqueous media such as micellar systems and cyclodextrins, and find out how these media can affect and control these reactions. This might have implications for fields such as cell biology, specifically for process occurring in living cells since both cyclodextrins and micelles might be considered simple models for protein and membranes in terms of their hydrophobicity. In addition, little information is known about bimolecular reactions involving two neutral reactants in non-ionic micelles where only the hydrophobic interaction is likely to influence the reaction due to the absence of charge-charge interaction. A kinetic and thermodynamic investigation of the reactions between peracids and different reductants i.e. iodide and series of aryl alkyl sulfides in presence non-ionic micelle and a- cyclodextrin is reported in this work. The kinetics were conducted by monitoring spectrophotometrically the increase or decrease in the absorbance due to formation of triioidide or disappearance of sulfides respectively, and absorbance versus time plots were fitted to nonlinear equation in order to obtain the observed pseudo first order rate constants. For reactions carried out in micellar systems the kinetic data were treated using the multiple micellar pseudophase model developed by Davies which considers the partition of reactants between water in the bulk aqueous phase and that in the micellar pseudophases. Important parameters in this model include the binding constant of reactants to Brij (non-ionic micelle) and kn. (reaction rate in micelle). For reactions in α-cyclodextrin, data was fitted to rate equations containing first and second order dependencies on cyclodextrin using non linear regression techniques. The work was carried out in the presence of 0.003 M nitric acid as reaction medium. The effect of inorganic electrolytes (sodium nitrate, sulfate, actetate, perchlorate and chloride) on the rate of oxidation of iodide in the absence and presence of non-ionic surfactant brij-35 was also studied. The critical micelle concentration (CMC) of the surfactants was determined using kinetic techniques and was found to be inversely proportional to the salt concentration and also to the temperature. The CMC was also found to decrease as the length of the hydrophobic part of the Brij surfactants was increased, possibly due to the decrease of interfacial energy on micellization, which generally increases in with increasing hydrophobic chain length. It was shown from analysis of the kinetic data that all non-ionic micelles in the (absence of salts) and a-CD studied in this work enhanced the rate of the iodide oxidation by MCPBA and that the rate showed saturation type kinetics. Sulfate ions were shown to accelerate the reaction further, whereas perchlorate caused an inhibition of the iodide oxidation (compared to the reaction only in nitric acid) in presence of Brij-35, but an increase in the presence of α-cyclodextrin. For the oxidation of sulfides by MCPBA in micelles and a-CD the observed rate increases to a maximum with increasing micelle or a-CD concentration and then subsequently declines. In the case of sulfide oxidation by the anionic peracid, peroxymonosulfate (PMS), there was only inhibition in the rate, due to separation of reactants. The effect of temperature on both rate and equilibrium processes for these systems was determined over the range 15 to 35°C. The results showed a linear decrease in the binding of metachloroperbenzoic (MCPBA) acid and aryl alkyl sulfides to both micelle and a-CD with increasing the temperature. The thermodynamic and activation parameters for the reactions were determined by using Van't Hoff and Eyring plots. Comparison of the micellar association constants of MCPBA and the apparent micellar association constant of the transition state for the reaction with iodide, suggested that orientational restriction imposed on the peracid by Brij-35 are similar to that in the transition state. For the same reactions carried out in α-cyclodextrin at different temperatures it was determined that the binding constant enthalpy and entropy of substrates, (peracid and iodide) are more negative than that obtained in the presence of brij-35 which indicates that stronger interactions are involved and more restriction imposed on the reactant in presence of a-CD compared to brij-35.A similar approach was employed for the reaction of series of aryl alkyl sulfides with peracids (PMS and MCPBA) in presence of Brij-35 and a-CD. The aryl alkyl sulfides can form both 1:1 and 2:1 host: guest complexes in cyclodextrin; the 2:1 inclusion complexes for some sulfides were larger than the 1:1 complexes, indicating cooperative binding, with the driving force for this possibly being a substrate induced dipole-dipole interaction between the two cyclodextrin molecules. Linear free energy studies indicate that the catalytic species is the bound peracid reacting with the unbound sulfides; sulfide binding results in steric inhibition of the reaction. The reaction of the non-binding PMS with sulfides results only in inhibition as cyclodextrin concentration is increased. The enthalpy and entropy for sulfide oxidation by peracids was calculated by means of a Van't Hoff plot. The reaction in a-CD associated with more negative entropy and enthalpy for the inclusion 2:1 while for 1:1 some substrates associated with positive entropy and small negative enthalpy while other show the usual behaviour observed for complex formation (negative values for both enthalpy and entropy).In all studied reactions (related reactions) there were good relationships between enthalpy and entropy (isokinetic relationships or enthalpy-entropy compensation). Whilst in some cases it is difficult to explain why enthalpy-entropy compensation might be observed, we have suggested that in the case of binding of sulfides to cyclodextrin these plots can act as probes into the orientation of the substrate within the cyclodextrin cavity. The nature of the catalytic mechanism for the reactions of peracids with sulfides and iodide in the presence of micelles and α-cyclodextrin was examined by comparing the transition state stabilisation parameters, KTsi, for the same reaction in the two catalytic systems. It was found that for three out of five sulfides the degree of transition state stabilisation was almost identical in both Brij-35 and α-cyclodextrin, perhaps suggesting the same catalytic mechanism in each system; this could be via either decreased stabilisation of the peracid ground state in the absence of a protic solvent and/or the prevention of significant charge development in the transition state as a result of an intramolecular proton transfer step involving the peracid that is facilitated by the absence of water. Other possibilities exist, such as general acid catalysis, though these would be more dependent on the nature of the catalytic system. There was a less clear relationship for iodide.

Η ύπαρξη αργιλικών ορυκτών εντός των ζωνών διάρρηξης επηρεάζει σημαντικά και ελέγχει τη μηχανική και σεισμική συμπεριφορά των ρηγμάτων. Ο σχηματισμός των μαλακών αργίλων σε πετρώματα ρηξιγενών ζωνών μπορεί να οδηγήσει σε εξασθένηση (fault zone weakening) της ζώνης διάρρηξης, καθώς και στην ανάπτυξη των ιστών μέσω αυθιγένεσης και μηχανικής περιστροφής, ενώ παράλληλα επηρεάζει τη διαπερατότητα της ζώνης διάρρηξης. Η παρουσία των αργιλικών ορυκτών σε πετρώματα ρηξιγενών ζωνών παίζει επίσης σπουδαίο ρόλο στην κυκλοφορία των ρευστών τόσο μέσα στον πυρήνα όσο και την ευρύτερη ζώνη διάρρηξης (damage zone). Στην παρούσα διπλωματική εργασία μελετήθηκε η ρηξιγενής ζώνη της Αρκίτσας, που αναπτύσσεται στο νότιο τμήμα του B. Ευβοϊκού κόλπου με γενική διεύθυνση ΑΒΑ-ΔΝΔ, με σκοπό να εξεταστεί αν η ρηξιγενής ζώνη αποτελεί δίαυλο ρευστής φάσης και να αναγνωριστούν τα πιθανά χαρακτηριστικά της κυκλοφορίας των ρευστών αυτών. Αντιπροσωπευτικά δείγματα πλούσια σε αργιλικό υλικό συλλέχθηκαν τόσο από τον πυρήνα του ρήγματος (fault core) όσο και από την ευρύτερη ζώνη διάρρηξης (fault damage zone). Τα δείγματα αναλύθηκαν με την χρήση περιθλασιμετρίας ακτίνων Χ, ηλεκτρονικής μικροσκοπίας σάρωσης και μικροανάλυσης. Στο κέντρο της ρηξιγενούς ζώνης αναγνωρίστηκαν αργιλικά ορυκτά όπως μοντμοριλλονίτης, κορρενσίτης και ιλλίτης καθώς και μικροκρυσταλλικός ασβεστίτης, δολομίτης, χαλαζίας, πλαγιόκλαστο και αλκαλικός άστριος. Η απουσία του κορρενσίτη από την ευρύτερη ζώνη διάρρηξης, ενός αργιλικού ορυκτού που συνήθως σχηματίζεται σε υδροθερμικές συνθήκες, υποδηλώνει ότι η κυκλοφορία των ρευστών περιορίστηκε κυρίως εντός και περιμετρικά του ρήγματος. Οι ορυκτολογικές παραγενέσεις στη ρηξιγενή ζώνη και κυρίως η παρουσία του κορρενσίτη, σε συνδυασμό με την απουσία του λομοντίτη, υποδεικνύουν συνθήκες υδροθερμικής εξαλλοίωσης σε ουδέτερο προς αλκαλικό περιβάλλον και σε θερμοκρασίες 100-150oC. / Clay minerals in shallow fault rocks are increasingly recognized as key to the mechanical and seismogenic behavior of faults and fluid flow circulation within the fault core and the surrounding damage zone. We therefore studied fault-gouge mineralogy from samples derived from the ENE-trending Arkitsa fault zone, in east-central Greece, in order to testify if the fault is acting as a channel for fluid flow and whether the conditions that characterize the flow can be identified. Clay-gouge samples were collected within the fault core zone, as well as in the broader fault damage area. Consequently, the samples were analyzed by X-Ray Diffraction, SEM and Electron microprobe analyses. The minerals that were identified within the centre of the fault zone are: Montmorillonite, corrensite, illite, micro-calcite, dolomite, quartz, plagioclase and K-feldspars. The absence of corrensite, a clay mineral usually formed in hydrothermal conditions, in the samples from the broader fault damage area indicates that the circulation of hydrothermal fluids is mostly confined within and around the fault core zone. The assemblages within the fault gouge zone and especially the presence of corrensite, combined with the absence of laumontite, indicate hydrothermal alteration at neutral to alkaline conditions and a temperature range at about 100-150 oC.

No description available.

No description available.

In this thesis, column experiments were conducted in order to determine the effect of irrigation with local groundwater on mobilization of lead and zinc in 50 years old sulfate-acid mine tailings. In addition, the influence of soluble oxalic acid, a common rhizosphere organic acid, was assessed by varying its concentration across an environmentally relevant range. In general, metal contaminant dissolution was not affected by the presence of oxalic acid. In both tailings, Zn mobilization was higher than Pb suggesting the presence of more kinetically labile Zn phases, regardless of the treatment used. Lead mobilization was also low because effluent solutions were near to equilibrium conditions with respect to gypsum, preventing Pb dissolution from Pb-sulfate minerals. Geochemical modeling also indicated that lead release was controlled by anglesite and plumbojarosite dissolution. Zinc release appears to be controlled by Zn-talc and goslarite.

This paper is part of a larger water quality study for Arizona (Marrero-Ortiz et al., 2009) and looks more closely at 22 water samples from 16 wells less than 250 feet deep in rural areas of southern Cochise County, Arizona. Nine wells were positive for total coliforms, four wells tested positive for fecal coliforms and one well tested positive for Escherichia coli. Nine wells were positive for enterococci and 13 were positive for Aeromonas hydrophila, some with very high levels. Fourteen of 21 possible metals were detected. All 16 wells contained barium. Ten wells were above limits for at least one primary contaminant (e.g., uranium or coliforms). Nine of the wells exceeded safe limits for at least one secondary contaminant (e.g. aluminum or total dissolved solids). Also found were weak correlations between microbes and metals including enterococci and arsenic, and Aeromonas hydrophila and manganese and uranium.

Epitaxial growth, or the oriented growth of a crystalline monolayer on an ordered substrate, appears in a wide range of systems and applications, from novel device fabrication to freshwater remediation. Despite this, methodical studies of the phenomenon are rare, and the mechanisms governing epitaxial growth are poorly understood. This investigation employs AFM techniques to monitor the epitaxial growth of ion crystal systems at the initial stages of growth. By using systems with well-known physical properties, we are able to relate growth modes to two key parameters, crystal lattice mismatch, Δr/r₀, and affinity between the overgrowth and the substrate ions, ξ. We found wetting growth occurs for systems in which Δr/r₀ is expansive (overgrowth lattice must expand to accommodate substrate) or mildly compressive (overgrowth compresses to accommodate substrate). Additionally, a strong affinity between the substrate and overgrowth ions, in combination with an expansive system, allows for epitaxial growth from undersaturated solutions. We also have observed several instances where the lateral force contrast on the growing film exhibits a strong dependence on the time of exposure to the growth solution and on the driving force for growth (solute concentration). We present results for three epitaxial growth systems in aqueous solutions: CaSO₃ on CaCO₃, PbSO₄ on BaSO₄, and BaSO₃ on BaSO₄. Chemically and topographically identical regions grown at higher concentrations exhibit higher friction than regions grown at lower concentrations. These observations suggest that epitaxial growth occurs by a fast condensation step incorporating a high defect density.

No description available.

The Mt. Milligan deposit is a tilted (~45°) Cu-Au alkalic porphyry located 155 km northwest of Prince George, B.C., Canada. It is the youngest of the BC alkalic porphyry deposits, all of which formed between 210 to 180 Ma in an extensive belt of K-enriched rocks related to the accretion of the Quesnellia-Stikinia superterrane to ancestral North America. Mt. Milligan has a measured and indicated resource of 205.9 million tonnes at 0.60 g/t Au and 0.25% Cu containing 3.7 million oz. gold, and 1.12 billion lb. copper. Shoshonitic volcanic and volcaniclastic andesites host mineralization. These have been intruded by a composite monzonitic stock (MBX stock), and associated sill (Rainbow Dike). Early disseminated chalcopyrite-magnetite and accessory quartz veins are associated with K-feldspar alteration in the MBX stock. A halo of biotite alteration with less extensive magnetite replaces host rocks within a ~150 m zone surrounding the stock, while K-feldpsar alteration extends along the Rainbow Dike and permeable epiclastic horizons. Peripheral albite-actinolite-epidote assemblages surround the K-silicate zone. Albite-actinolite occurs at depth, and epidote dominates laterally. Copper and Au grade are maximal where the albite-actinolite assemblage overprints biotite alteration. Gold grade is moderate in association with epidote, whereas Cu is depleted. The post-mineral Rainbow Fault separates the core Cu-rich zone from a downthrown Au-rich zone. A similar zonation of metals occurs in the hanging-wall (66 zone), where a Cu-bearing, potassically-altered trachytic horizon transitions to a funnel-shaped zone of pyrite-dolomite-sericite-chlorite alteration with elevated gold. Sulfide S-isotope compositions range from -4.79 δ34S in the central Cu-Au orebody to near-zero values at the system periphery, typical of alkalic porphyries. Sulfur isotope contours reflect the magmatic-hydrothermal fluid evolution, and indicate late-stage ingress of peripheral fluids into the Cu-Au zone. Carbonate C- and O-isotope compositions corroborate the magmatic fluid path from the Cu-Au rich zone to Au-rich zone with decreasing depth. Strontium isotopic compositions of peripheral alteration minerals indicate a laterally increasing meteoric fluid component. Changes in major- and trace element composition of epidote and pyrite across the deposit are also systematic. These provide additional vectors to ore, and confirm the kinematics of the Rainbow Fault.