Uranium mineralization in the Guindani Canyon area of the northern Whetstone Mountains, Cochise County, Arizona

Rain and snow contain dissolved oxygen because of equilibration with atmospheric oxygen. In contrast, groundwater deep in the Earth, especially at depths of hundreds to thousands of meters, contains little dissolved oxygen. As erosion gradually lowers the Earth’s surface, oxygen-bearing groundwater gradually gains access to rock within the Earth that had not previously been exposed to oxidizing conditions. Uranium is generally stable under anoxic conditions, but is dissolved and transported by oxidizing waters. Gradual downward movement of uranium with a lowering groundwater table may produce a uranium enrichment zone at depth (supergene enrichment) overlain by rocks that have been depleted in uranium. Uranium may also be carried laterally for great distances away from sites where it was dissolved, and may be concentrated in secondary, supergene deposits.Documents in the AZGS Documents Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact [email protected])

Uranium mineralization in the Guindani Canyon area of the northern Whetstone Mountains, Cochise County, Arizona

Rain and snow contain dissolved oxygen because of equilibration with atmospheric oxygen. In contrast, groundwater deep in the Earth, especially at depths of hundreds to thousands of meters, contains little dissolved oxygen. As erosion gradually lowers the Earth’s surface, oxygen-bearing groundwater gradually gains access to rock within the Earth that had not previously been exposed to oxidizing conditions. Uranium is generally stable under anoxic conditions, but is dissolved and transported by oxidizing waters. Gradual downward movement of uranium with a lowering groundwater table may produce a uranium enrichment zone at depth (supergene enrichment) overlain by rocks that have been depleted in uranium. Uranium may also be carried laterally for great distances away from sites where it was dissolved, and may be concentrated in secondary, supergene deposits.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact [email protected]

Enhanced bioaffinity sensing using surface plasmons, surface enzyme reactions, nanoparticles and diffraction gratings

This paper introduces a novel approach to surface bioaffinity sensing based on the adsorption of nanoparticles onto a gold diffraction grating that supports the excitation of planar surface plasmons. A surface enzymatic amplification reaction is also incorporated into the detection scheme to enhance the sensitivity and utility of the nanoparticle-enhanced diffraction grating (NEDG) sensors. As a demonstration, the detection of microRNA is described where a combination of a surface polymerase reaction and DNA-modified nanoparticles is used to detect the bioaffinity adsorption of the target onto the probe-functionalized gold grating surface. The enzymatically-amplified NEDG sensors possess a great potential for a wide range of applications including the detection of biosecurity agents, DNA and RNA viruses, biomarkers, and proteins

Long-range surface plasmon resonance imaging for bioaffinity sensing

A novel bioaffinity sensor based on surface plasmon resonance (SPR) imaging measurements of a multiple-layered structure that supports the generation of long-range surface plasmons (LRSPs) at the water−metal interface is reported. LRSPs possess longer surface propagation lengths, higher electric field strengths, and sharper angular resonance curves than conventional surface plasmons. LRSPR imaging is a version of SPR imaging that requires a symmetric dielectric arrangement around the gold thin film. This arrangement is created using an SF10 prism/Cytop/gold/water multilayer film structure where Cytop is an amorphous fluoropolymer with a refractive index very close to that of water. LRSPR imaging experiments are performed at a fixed incident angle and lead to an enhanced response for the detection of surface binding interactions. As an example, the hybridization adsorption of a 16-mer single-stranded DNA (ssDNA) onto a two-component ssDNA array was monitored with LRSPR imaging. The ssDNA array was created using a new fabrication technology appropriate for the LRSPR multilayers

Creating advanced multifunctional biosensors with surface enzymatic transformations

This paper summarizes our recent work on the coupling of surface enzyme chemistry and bioaffinity interactions on biopolymer microarrays for the creation of multiplexed biosensors with enhanced selectivity and sensitivity. The surface sensitive techniques of surface plasmon resonance imaging (SPRI) and surface plasmon fluorescence spectroscopy (SPFS) are used to detect the surface enzymatic transformations in real time. Three specific examples of novel coupled surface bioaffinity/surface enzymatic processes are demonstrated: (i) a surface enzymatic amplification method utilizing the enzyme ribonuclease H (RNase H) in conjunction with RNA microarrays that permits the ultrasensitive direct detection of genomic DNA at a concentration of 1 fM without labeling or PCR amplification, (ii) the use of RNADNA ligation chemistry to create renewable RNA microarrays from single stranded DNA microarrays, and (iii) the application of T7RNApolymerase for the on-chip replication ofRNAfrom double strandedDNAmicroarray elements. In addition, a simple yet powerful theoretical framework that includes the contributions of both enzyme adsorption and surface enzyme kinetics is used to quantitate surface enzyme reactivity. This model is successfully applied to SPRI and SPFS measurements of surface hydrolysis reactions of RNase H and Exonuclease III (Exo III) on oligonucleotide microarray

Attomole detection of microRNAs by nanoparticle-amplified SPR imaging measurements of surface polyadenylation reactions

Multiple microRNAs (miRNAs) are detected in a microarray format using a novel approach that combines a surface enzyme reaction with nanoparticle-amplified SPR imaging (SPRI). The surface reaction of poly(A) polymerase creates poly(A) tails on miRNAs hybridized onto locked nucleic acid (LNA) microarrays. DNA-modified nanoparticles are then adsorbed onto the poly(A) tails and detected with SPRI. This ultrasensitive nanoparticle-amplified SPRI methodology can be used for miRNA profiling at attomole levels