Exploring Laser Induced Breakdown Spectroscopy (LIBS) for Post-Detonation Nuclear Forensics Debris Analysis

In the unlikely but catastrophic event of a nuclear terrorist attack our government leadership will need reliable information to rapidly inform critical decisions. This research explores the use of Laser Induced Breakdown Spectroscopy (LIBS) as a potential analysis tool in the National Technical Nuclear Forensics process. The current state of post detonation nuclear forensics requires ground and air samples be collected and shipped to state-of-the-art laboratories for radiochemical analysis. The samples undergo many measurements and useable data is produced as these measurements are completed. This data flows back into the process to guide additional measurements and inform the process of narrowing down the origin of the nuclear materials. This is a time-consuming process in need of new analytical methods that can be performed in situ. It is clear that LIBS will not be able to perform all of the measurements needed but the intent of this project is to explore where a LIBS system deployed with a ground collection team could provide meaningful data more quickly than the traditional radiochemistry processes. My research will include calibrating and optimizing LIBS system at the United States Military Academy and conducting analysis of Trinitite (glass like debris from the first nuclear weapon test) and a surrogate material produced by University of Tennessee at Knoxville. The intent of the surrogate material is to be used during post-detonation nuclear forensics exercises. The analysis will include optimizing collection parameters for the glass-like samples, comparison of key constituents in Trinitite and the surrogate material, and characterizing the effects of sample non-homogeneity

Sedimentary talc in Neoproterozoic carbonate successions

Mineralogical, petrographic and sedimentological observations document early diagenetic talc in carbonate-dominated successions deposited on two early Neoproterozoic (~ 800–700 million years old) platform margins. In the Akademikerbreen Group, Svalbard, talc occurs as nodules that pre-date microspar cements that fill molar tooth structures and primary porosity in stromatolitic carbonates. In the upper Fifteenmile Group of the Ogilvie Mountains, NW Canada, the talc is present as nodules, coated grains, rip-up clasts and massive beds that are several meters thick. To gain insight into the chemistry required to form early diagenetic talc, we conducted precipitation experiments at 25 °C with low-SO4 synthetic seawater solutions at varying pH, Mg2+ and SiO2(aq). Our experiments reveal a sharp and reproducible pH boundary (at ~ 8.7) only above which does poorly crystalline Mg-silicate precipitate; increasing Mg2+ and/or SiO2(aq) alone is insufficient to produce the material. The strong pH control can be explained by Mg-silica complexing activated by the deprotonation of silicic acid above ~ 8.6–8.7. FT-IR, TEM and XRD of the synthetic precipitates reveal a talc-like 2:1 trioctahedral structure with short-range stacking order. Hydrothermal experiments simulating burial diagenesis show that dehydration of the precipitate drives a transition to kerolite (hydrated talc) and eventually to talc. This formation pathway imparts extensive layer stacking disorder to the synthetic talc end-product that is identical to Neoproterozoic occurrences. Early diagenetic talc in Neoproterozoic carbonate platform successions appears to reflect a unique combination of low Al concentrations (and, by inference, low siliciclastic input), near modern marine salinity and Mg2+, elevated SiO2(aq), and pH > ~ 8.7. Because the talc occurs in close association with microbially influenced sediments, we suggest that soluble species requirements were most easily met through microbial influences on pore water chemistry, specifically pH and alkalinity increases driven by anaerobic Fe respiration.Organismic and Evolutionary Biolog

Shed urinary ALCAM is an independent prognostic biomarker of three-year overall survival after cystectomy in patients with bladder cancer.

Proteins involved in tumor cell migration can potentially serve as markers of invasive disease. Activated Leukocyte Cell Adhesion Molecule (ALCAM) promotes adhesion, while shedding of its extracellular domain is associated with migration. We hypothesized that shed ALCAM in biofluids could be predictive of progressive disease. ALCAM expression in tumor (n = 198) and shedding in biofluids (n = 120) were measured in two separate VUMC bladder cancer cystectomy cohorts by immunofluorescence and enzyme-linked immunosorbent assay, respectively. The primary outcome measure was accuracy of predicting 3-year overall survival (OS) with shed ALCAM compared to standard clinical indicators alone, assessed by multivariable Cox regression and concordance-indices. Validation was performed by internal bootstrap, a cohort from a second institution (n = 64), and treatment of missing data with multiple-imputation. While ALCAM mRNA expression was unchanged, histological detection of ALCAM decreased with increasing stage (P = 0.004). Importantly, urine ALCAM was elevated 17.0-fold (P < 0.0001) above non-cancer controls, correlated positively with tumor stage (P = 0.018), was an independent predictor of OS after adjusting for age, tumor stage, lymph-node status, and hematuria (HR, 1.46; 95% CI, 1.03-2.06; P = 0.002), and improved prediction of OS by 3.3% (concordance-index, 78.5% vs. 75.2%). Urine ALCAM remained an independent predictor of OS after accounting for treatment with Bacillus Calmette-Guerin, carcinoma in situ, lymph-node dissection, lymphovascular invasion, urine creatinine, and adjuvant chemotherapy (HR, 1.10; 95% CI, 1.02-1.19; P = 0.011). In conclusion, shed ALCAM may be a novel prognostic biomarker in bladder cancer, although prospective validation studies are warranted. These findings demonstrate that markers reporting on cell motility can act as prognostic indicators

Stratigraphic evolution of the Neoproterozoic Callison Lake Formation: Linking the break-up of Rodinia to the Islay carbon isotope excursion

The ∼780 to 540 Ma Windermere Supergroup of western North America records the protracted development of the western Laurentian passive margin and provides insights into the nature, timing, and kinematics of Rodinia's fragmentation. Here we present a refined tectono- and chemo-stratigraphic model for circa 780 to 720 Ma sedimentation in NW Canada through a study of the Callison Lake Formation (formalized herein) of the Mount Harper Group, spectacularly exposed in the Coal Creek and Hart River inliers of the Ogilvie Mountains of Yukon, Canada. Twenty-one stratigraphic sections are integrated with geological mapping, facies analysis, carbon and oxygen isotope chemostratigraphy, and Re-Os geochronology to provide a depositional reconstruction for the Callison Lake Formation. Mixed siliciclastic, carbonate, and evaporite sediments accumulated in marginal marine embayments formed in discrete hangingwall depocenters of a prominent Windermere extensional fault zone. Deposition of the Windermere Supergroup in NW Canada post dates the eruption of the circa 780 Ma Gunbarrel Large Igneous Province by ∼30 million years, is locally associated with compressional or transpressional tectonism, and predates the successful rift-drift transition by ∼200 million years. In order to accommodate evidence for coeval extensional and compressional tectonism, abrupt facies change, and Neoproterozoic fault geometries, we propose that NW Laurentia experienced strike-slip deformation during the ∼740 to 660 Ma early fragmentation of the supercontinent Rodinia. Sequence stratigraphic data from the Callison Lake Formation and other basal Windermere successions in the northern Canadian Cordillera delineate three distinct depositional sequences, or transgressive-regressive (T-R) cycles, that are coeval with similar stratigraphic packages in the ∼780 to 720 Ma Chuar-Uinta Mountain-Pahrump basins of the western United States. The global circa 735 Ma Islay carbon isotope excursion is consistently present in carbonate strata of the third T-R cycle and is interpreted to represent a primary perturbation to the global carbon cycle, possibly driven by the uplift and weathering of extensive shallow epicontinental seaways and evaporite basins.Earth and Planetary Science

Active Ooid Growth Driven By Sediment Transport in a High-Energy Shoal, Little Ambergris Cay, Turks and Caicos Islands

Ooids are a common component of carbonate successions of all ages and present significant potential as paleoenvironmental proxies, if the mechanisms that control their formation and growth can be understood quantitatively. There are a number of hypotheses about the controls on ooid growth, each offering different ideas on where and how ooids accrete and what role, if any, sediment transport and abrasion might play. These hypotheses have not been well tested in the field, largely due to the inherent challenges of tracking individual grains over long timescales. This study presents a detailed field test of ooid-growth hypotheses on Little Ambergris Cay in the Turks and Caicos Islands, British Overseas Territories. This field site is characterized by westward net sediment transport from waves driven by persistent easterly trade winds. This configuration makes it possible to track changes in ooid properties along their transport path as a proxy for changes in time. Ooid size, shape, and radiocarbon age were compared along this path to determine in which environments ooids are growing or abrading. Ooid surface textures, petrographic fabrics, stable-isotope compositions (δ^(13)C, δ^(18)O, and δ^(34)S), lipid geochemistry, and genetic data were compared to characterize mechanisms of precipitation and degradation and to determine the relative contributions of abiotic (e.g., abiotic precipitation, physical abrasion) and biologically influenced processes (e.g., biologically mediated precipitation, fabric destruction through microbial microboring and micritization) to grain size and character. A convergence of evidence shows that active ooid growth occurs along the transport path in a high-energy shoal environment characterized by frequent suspended-load transport: median ooid size increases by more than 100 μm and bulk radiocarbon ages decrease by 360 yr westward along the ∼ 20 km length of the shoal crest. Lipid and 16S rRNA data highlight a spatial disconnect between the environments with the most extensive biofilm colonization and environments with active ooid growth. Stable-isotope compositions are indistinguishable among samples, and are consistent with abiotic precipitation of aragonite from seawater. Westward increases in ooid sphericity and the abundance of well-polished ooids illustrate that ooids experience subequal amounts of growth and abrasion—in favor of net growth—as they are transported along the shoal crest. Overall, these results demonstrate that, in the Ambergris system, the mechanism of ooid growth is dominantly abiotic and the loci of ooid growth is determined by both carbonate saturation and sediment transport mode. Microbes play a largely destructive, rather than constructive, role in ooid size and fabric

Active Ooid Growth Driven By Sediment Transport in a High-Energy Shoal, Little Ambergris Cay, Turks and Caicos Islands

Ooids are a common component of carbonate successions of all ages and present significant potential as paleoenvironmental proxies, if the mechanisms that control their formation and growth can be understood quantitatively. There are a number of hypotheses about the controls on ooid growth, each offering different ideas on where and how ooids accrete and what role, if any, sediment transport and abrasion might play. These hypotheses have not been well tested in the field, largely due to the inherent challenges of tracking individual grains over long timescales. This study presents a detailed field test of ooid-growth hypotheses on Little Ambergris Cay in the Turks and Caicos Islands, British Overseas Territories. This field site is characterized by westward net sediment transport from waves driven by persistent easterly trade winds. This configuration makes it possible to track changes in ooid properties along their transport path as a proxy for changes in time. Ooid size, shape, and radiocarbon age were compared along this path to determine in which environments ooids are growing or abrading. Ooid surface textures, petrographic fabrics, stable-isotope compositions (δ^(13)C, δ^(18)O, and δ^(34)S), lipid geochemistry, and genetic data were compared to characterize mechanisms of precipitation and degradation and to determine the relative contributions of abiotic (e.g., abiotic precipitation, physical abrasion) and biologically influenced processes (e.g., biologically mediated precipitation, fabric destruction through microbial microboring and micritization) to grain size and character. A convergence of evidence shows that active ooid growth occurs along the transport path in a high-energy shoal environment characterized by frequent suspended-load transport: median ooid size increases by more than 100 μm and bulk radiocarbon ages decrease by 360 yr westward along the ∼ 20 km length of the shoal crest. Lipid and 16S rRNA data highlight a spatial disconnect between the environments with the most extensive biofilm colonization and environments with active ooid growth. Stable-isotope compositions are indistinguishable among samples, and are consistent with abiotic precipitation of aragonite from seawater. Westward increases in ooid sphericity and the abundance of well-polished ooids illustrate that ooids experience subequal amounts of growth and abrasion—in favor of net growth—as they are transported along the shoal crest. Overall, these results demonstrate that, in the Ambergris system, the mechanism of ooid growth is dominantly abiotic and the loci of ooid growth is determined by both carbonate saturation and sediment transport mode. Microbes play a largely destructive, rather than constructive, role in ooid size and fabric

Sedimentology, chemostratigraphy, and stromatolites of lower Paleoproterozoic carbonates, Turee Creek Group, Western Australia

The ca. 2.45–2.22 Ga Turee Creek Group, Western Australia, contains carbonate- rich horizons that postdate earliest Proterozoic iron formations, bracket both Paleoproterozoic glaciogenic beds and the onset of the Great Oxidation Event (GOE), and predate ca. 2.2–2.05 Ga Lomagundi-Jatuli C-isotopic excursion(s). As such, Turee Creek carbonate strata provide an opportunity to characterize early Paleoproterozoic carbonate sedimentation and carbon cycle dynamics in the context of significant global change. Here, we report on the stratigraphy, sedimentology, petrology, carbon isotope chemostratigraphy, and stromatolite development for carbonate-rich successions within the pre-glacial part of the Kungarra Formation and the postglacial Kazput Formation. Kungarra carbonate units largely occur as laterally discontinuous beds within a thick, predominantly siliciclastic shelf deposit. While this succession contains thin microbialite horizons, most carbonates consist of patchy calcite overgrowths within a siliciclastic matrix. C-isotopic values show marked variation along a single horizon and even within hand samples, reflecting spatially and temporally variable mixing between dissolved inorganic carbon in seawater and isotopically light inorganic carbon generated via syn- and post-depositional remineralization of organic matter. In contrast, the Kazput carbonates consist of subtidal stromatolites, grainstones, and micrites deposited on a mixed carbonate-siliciclastic shelf. These carbonates exhibit moderate δ13 C values of -2‰ to +1.5‰ and likely preserve a C-isotopic signature of seawater. Kazput carbonates, thus, provide some of the best available evidence that an interval of unexceptional C-isotopic values separates the Lomagundi-Jatuli C-isotopic excursion(s) from the initiation of the GOE as inferred from multiple sulfur isotopes (loss 4 of mass independent fractionation). The Kazput Formation also contains unusual, m-scale stromatolitic buildups, which are composed of sub-mm laminae and discontinuous, convex upward lenticular precipitates up to a few mm in maximum thickness. Laminae, interpreted as microbial mat layers, contain quartz and clay minerals as well as calcite, whereas precipitate lenses consist of interlocking calcite anhedra, sometimes showing faint mm-scale banding. These cements formed either as infillings of primary voids formed by gas emission within penecontemporaneously lithified mats, or as local seafloor precipitates that formed on, or within, surface mats. It is possible that both mechanisms interacted to form the unique Kazput stromatolites. These microbialites speak to a distinctive interaction between life and environment early in the Paleoproterozoic Era.Earth and Planetary Science

Chemical Interactions and Their Role in the Microphase Separation of Block Copolymer Thin Films

The thermodynamics of self-assembling systems are discussed in terms of the chemical interactions and the intermolecular forces between species. It is clear that there are both theoretical and practical limitations on the dimensions and the structural regularity of these systems. These considerations are made with reference to the microphase separation that occurs in block copolymer (BCP) systems. BCP systems self-assemble via a thermodynamic driven process where chemical dis-affinity between the blocks driving them part is balanced by a restorative force deriving from the chemical bond between the blocks. These systems are attracting much interest because of their possible role in nanoelectronic fabrication. This form of self-assembly can obtain highly regular nanopatterns in certain circumstances where the orientation and alignment of chemically distinct blocks can be guided through molecular interactions between the polymer and the surrounding interfaces. However, for this to be possible, great care must be taken to properly engineer the interactions between the surfaces and the polymer blocks. The optimum methods of structure directing are chemical pre-patterning (defining regions on the substrate of different chemistry) and graphoepitaxy (topographical alignment) but both centre on generating alignment through favourable chemical interactions. As in all self-assembling systems, the problems of defect formation must be considered and the origin of defects in these systems is explored. It is argued that in these nanostructures equilibrium defects are relatively few and largely originate from kinetic effects arising during film growth. Many defects also arise from the confinement of the systems when they are ‘directed’ by topography. The potential applications of these materials in electronics are discussed

Surface processes recorded by rocks and soils on Meridiani Planum, Mars: Microscopic Imager observations during Opportunity's first three extended missions

The Microscopic Imager (MI) on the Mars Exploration Rover Opportunity has returned images of Mars with higher resolution than any previous camera system, allowing detailed petrographic and sedimentological studies of the rocks and soils at the Meridiani Planum landing site. Designed to simulate a geologist's hand lens, the MI is mounted on Opportunity's instrument arm and can resolve objects 0.1 mm across or larger. This paper provides an overview of MI operations, data calibration, and analysis of MI data returned during the first 900 sols (Mars days) of the Opportunity landed mission. Analyses of Opportunity MI data have helped to resolve major questions about the origin of observed textures and features. These studies support eolian sediment transport, rather than impact surge processes, as the dominant depositional mechanism for Burns formation strata. MI stereo observations of a rock outcrop near the rim of Erebus Crater support the previous interpretation of similar sedimentary structures in Eagle Crater as being formed by surficial flow of liquid water. Well-sorted spherules dominate ripple surfaces on the Meridiani plains, and the size of spherules between ripples decreases by about 1 mm from north to south along Opportunity's traverse between Endurance and Erebus craters