Oxygen penetration and mineral stability within the San Manuel tailings, AZ

2018 ◽  
Vol 19 (3) ◽  
pp. 255-268
Author(s):  
J. Declercq ◽  
R. J. Bowell
Keyword(s):  
Oxygen Penetration ◽  
Mineral Stability

scholarly journals Bodipy-Loaded Micelles Based on Polylactide as Surface Coating for Photodynamic Control of Staphylococcus aureus

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 223
Author(s):  
Enrico Caruso ◽  
Viviana Teresa Orlandi ◽  
Miryam Chiara Malacarne ◽  
Eleonora Martegani ◽  
Chiara Scanferla ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Pathogenic Bacteria ◽  
Surface Coatings ◽  
Supramolecular System ◽  
Amphiphilic Copolymers ◽  
Oxygen Penetration ◽  
Short Period ◽  
Excellent Activity ◽  
Coating Matrix ◽  
Photodynamic Control

Decontaminating coating systems (DCSs) represent a challenge against pathogenic bacteria that may colonize hospital surfaces, causing several important infections. In this respect, surface coatings comprising photosensitizers (PSs) are promising but still controversial for several limitations. PSs act through a mechanism of antimicrobial photodynamic inactivation (aPDI) due to formation of reactive oxygen species (ROS) after light irradiation. However, ROS are partially deactivated during their diffusion through a coating matrix; moreover, coatings should allow oxygen penetration that in contact with the activated PS would generate 1O2, an active specie against bacteria. In the attempt to circumvent such constraints, we report a spray DCS made of micelles loaded with a PS belonging to the BODIPY family (2,6-diiodo-1,3,5,7-tetramethyl-8-(2,6-dichlorophenyl)-4,4′-difluoroboradiazaindacene) that is released in a controlled manner and then activated outside the coating. For this aim, we synthesized several amphiphilic copolymers (mPEG–(PLA)n), which form micelles, and established the most stable supramolecular system in terms of critical micelle concentration (CMC) and ∆Gf values. We found that micelles obtained from mPEG–(PLLA)2 were the most thermodynamically stable and able to release BODIPY in a relatively short period of time (about 80% in 6 h). Interestingly, the BODIPY released showed excellent activity against Staphylococcus aureus even at micromolar concentrations.

scholarly journals Thermodynamic Stabilities of U(VI) Minerals: Estimated and Observed Relationships

1996 ◽  
Vol 465 ◽  
Author(s):  
Robert J. Finch
Keyword(s):  
Gibbs Energy ◽  
Reaction Pathways ◽  
Free Energies ◽  
Fine Grained ◽  
Surface Energies ◽  
Stability Diagrams ◽  
Activity Diagrams ◽  
Mineral Stability ◽  
Mineral Compositions

ABSTRACTGibbs free energies of formation (ΔG°ƒ) for several structurally related U(VI) minerals are estimated by summing the Gibbs energy contributions from component oxides. The estimated ΔG°f values are used to construct activity-activity (stability) diagrams, and the predicted stability fields are compared with observed mineral occurrences and reaction pathways. With some exceptions, natural occurrences agree well with the mineral stability fields estimated for the systems Sio2-Cao-Uo3-UOH2O and Co2-caO-UO3-H2O providing confidence in the estimated thermodynamic values. Activity-activity diagrams are sensitive to small differences in ΔG°f values, and mineral compositions must be known accurately, including structurally bound H2O. The estimated ΔG°f values are not considered reliable for a few minerals for two major reasons: (1) the structures of the minerals in question are not closely similar to those used to estimate the ΔG°f* values of the component oxides, and/or (2) the minerals in question are exceptionally fine grained, leading to large surface energies that increase the effective mineral solubilities.

scholarly journals Use of an oxygen planar optode to assess the effect of high velocity microsprays on oxygen penetration in a human dental biofilms in-vitro

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Yalda Khosravi ◽  
Rala D.P. Kandukuri ◽  
Sara R. Palmer ◽  
Erin S. Gloag ◽  
Sergey M. Borisov ◽  
...  
Keyword(s):  
High Velocity ◽  
Oxygen Penetration ◽  
Planar Optode

scholarly journals Luminescent Nanosensors for Ratiometric Monitoring of Three-Dimensional Oxygen Gradients in Laboratory and Clinical Pseudomonas aeruginosa Biofilms

2019 ◽  
Vol 85 (20) ◽  
Author(s):  
Megan P. Jewell ◽  
Anne A. Galyean ◽  
J. Kirk Harris ◽  
Edith T. Zemanick ◽  
Kevin J. Cash
Keyword(s):  
Cystic Fibrosis ◽  
Pseudomonas Aeruginosa ◽  
Temporal Variation ◽  
Complex Structure ◽  
Three Dimensional ◽  
Spatial And Temporal Variation ◽  
Content Type ◽  
Oxygen Penetration ◽  
Oxygen Gradients ◽  
Oxygen Sensitive

ABSTRACT Bacterial biofilms can form persistent infections on wounds and implanted medical devices and are associated with many chronic diseases, such as cystic fibrosis. These infections are medically difficult to treat, as biofilms are more resistant to antibiotic attack than their planktonic counterparts. An understanding of the spatial and temporal variation in the metabolism of biofilms is a critical component toward improved biofilm treatments. To this end, we developed oxygen-sensitive luminescent nanosensors to measure three-dimensional (3D) oxygen gradients, an application of which is demonstrated here with Pseudomonas aeruginosa biofilms. The method was applied here and improves on traditional one-dimensional (1D) methods of measuring oxygen profiles by investigating the spatial and temporal variation of oxygen concentration when biofilms are challenged with antibiotic attack. We observed an increased oxygenation of biofilms that was consistent with cell death from comparisons with antibiotic kill curves for PAO1. Due to the spatial and temporal nature of our approach, we also identified spatial and temporal inhomogeneities in the biofilm metabolism that are consistent with previous observations. Clinical strains of P. aeruginosa subjected to similar interrogation showed variations in resistance to colistin and tobramycin, which are two antibiotics commonly used to treat P. aeruginosa infections in cystic fibrosis patients. IMPORTANCE Biofilm infections are more difficult to treat than planktonic infections for a variety of reasons, such as decreased antibiotic penetration. Their complex structure makes biofilms challenging to study without disruption. To address this limitation, we developed and demonstrated oxygen-sensitive luminescent nanosensors that can be incorporated into biofilms for studying oxygen penetration, distribution, and antibiotic efficacy—demonstrated here with our sensors monitoring antibiotic impacts on metabolism in biofilms formed from clinical isolates. The significance of our research is in demonstrating not only a nondisruptive method for imaging and measuring oxygen in biofilms but also that this nanoparticle-based sensing platform can be modified to measure many different ions and small molecule analytes.

scholarly journals Characterization of Anaerobic Biofilms Growing on Carbon Felt Bioanodes Exposed to Air

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1341
Author(s):  
Raúl M. Alonso ◽  
Guillermo Pelaz ◽  
María Isabel San-Martín ◽  
Antonio Morán ◽  
Adrián Escapa
Keyword(s):  
Normal Operation ◽  
Carbon Felt ◽  
Dissolved Oxygen Concentration ◽  
Oxygen Penetration ◽  
Long Period ◽  
And Performance ◽  
Catalytic Capacity ◽  
Felt Electrodes

The role of oxygen in anodic biofilms is still a matter of debate. In this study, we tried to elucidate the structure and performance of an electrogenic biofilm that develops on air-exposed, carbon felt electrodes, commonly used in bioelectrochemical systems. By simultaneously recording the current density produced by the bioanode and dissolved oxygen concentration, both inside and in the vicinity of the biofilm, it was possible to demonstrate the influence of a protective aerobic layer present in the biofilm (mainly formed by Pseudomonas genus bacteria) that prevents electrogenic bacteria (such as Geobacter sp.) from hazardous exposure to oxygen during its normal operation. Once this protective barrier was deactivated for a long period of time, the catalytic capacity of the biofilm was severely affected. In addition, our results highlighted the importance of the material’s porous structure for oxygen penetration in the electrode.

Rates of microbial processes in sediments

1993 ◽  
Vol 344 (1670) ◽  
pp. 49-58 ◽  
Keyword(s):  
Organic Matter ◽  
Simulation Model ◽  
Sediment Surface ◽  
Concentration Profiles ◽  
Water Interface ◽  
Organic Loading ◽  
Linear Gradient ◽  
Oxygen Penetration ◽  
And Diffusion ◽  
Methods Of Measurement

The following methods of measurement of sediment parameters are discussed: (1) rate of diffusional exchange of reactants and products across the sediment—water interface; (2) the concentration profiles of these reactants and profiles in the sediment, and (3) profiles and integrated rates of reactions in the sediment. The interaction of the processes of reaction and diffusion are illustrated using a simulation model. The effect of increasing organic loading (6.2, 37.2 and 62.0 mmol C m -2 d -1 ), with organic matter distributed in three ways: close to the sediment surface, a linear gradient downwards or evenly mixed throughout the sediment. Predictable increases in anoxic processes occurred with increasing organic loading. There were higher diffusional losses of dissolved organic matter when organic degradation occurred close to the sediment—water interface. The model predicted that degradation of organic matter at depth could have the following effects: an increase in the depth of oxygen penetration, an increase in the ratio of CO 2 /O 2 , and an increase in nitrification and denitrification.

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