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<strong>Distribution and Interaction of Lead (Pb), Mercury (Hg), Selenium (Se), and Other Metals in Brain Tissue Using Synchrotron Micro-X-ray Fluorescence</strong>Alexis Webb (16642248) 01 August 2023 (has links)
<p>Alzheimer’s disease (AD) is a progressive neurodegenerative disease affecting more than 6 million individuals in the United States and more than 50 million worldwide. Currently, there exists no cure for AD and there are very few treatments to limit disease progression. Understanding the mechanisms through which AD develops and the risk factors associated with disease onset and progression is imperative in diagnosis and treatment of AD. Metal dysregulation has been implicated in disease pathogenesis through a number of mechanisms. Toxic heavy metals, such as lead (Pb) and mercury (Hg) are known to have deleterious effects on the central nervous system (CNS) and have been shown to increase AD pathology in animal models. However, there are significant knowledge gaps on how these metals deposit in human and animal brains at the microscopic scale, how they interact with essential metals in brain, and the relation of heavy metal exposure and AD. In this project, we aimed to investigate the distribution of heavy metals and their interactions with essential elements in transgenic mouse and human brain tissue models. We report, for the first time, Pb distribution and its co-deposition with Se in mouse brains following subchronic Pb exposure, Hg distribution and its co-deposition with Se in post-mortem AD and no cognitive impairment (NCI) brains, and the association of Pb, Hg, and other metals in these brains. All the data were obtained using synchrotron x-ray fluorescence (XRF), a powerful technique that allows for localization and quantification of multiple biological elements, as well as heavy metals, with a high spatial resolution and low detection limit. The work will shed light on the role essential metals, especially Se, play in neurotoxicity of Pb and Hg, and pave the way for potential future directions on heavy metal exposure and neurodegeneration.</p>
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Elemental distribution in the catchment around Lake Victoria in KenyaEnander, Frida January 2017 (has links)
Lake Victoria, the second largest freshwater body in the world is affected by rise in eutrophication. This is mainly due to anthropogenic activities happening in the catchment. In this study, distribution of six elements (Cu, Zn, N, C, P, and Si) in sediments were studied from the five sites in Kenya namely Kisumu (DK2, OK2), Busia (KK2), Siaya (SPK2 and Kapsabet (KP1A). The elemental flux values were correlated with historical changes in the catchment to see if it can influence the eutrophication in Lake Victoria. Flux calculated for these elements show a strong correlation with anthropogenic activities associated with land-use changes ushered after building of the railroads, agricultural practices and urban development in the catchment. The spatial and temporal changes in distribution of these elements have a distinct signature on the metal flux. The metal flux are correlated with change in trophic conditions in the lake. There is also a distinct difference in metal flux into the lake derived from urban versus rural areas.
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Modeling and Applications of Ferroelectric Based DevicesAtanu Kumar Saha (11209926) 30 July 2021 (has links)
<p>To sustain the upcoming paradigm shift in computations
technology efficiently, innovative solutions at the lowest level of the
computing hierarchy (the material and device level) are essential to delivering
the required functionalities beyond what is available with current CMOS platforms.
Motivated by this, in this dissertation, we explore ferroelectric-based devices
for steep-slope logic and energy-efficient non-volatile-memory functionalities
signifying the novel device attributes, possibilities for continual dimensional
scaling with the much-needed enhancement in performance.</p>
<p> </p>
<p>Among various ferroelectric (FE) materials, Zr doped HfO<sub>2</sub>
(HZO) has gained immense research attention in recent times by virtue of CMOS
process compatibility and a considerable amount of ferroelectricity at room
temperature. In this work, we investigate the Zr concentration-dependent
crystal phase transition of Hf<sub>1-x</sub>Z<sub>x</sub>O<sub>2</sub> (HZO)
and the corresponding evolution of dielectric, ferroelectric, and
anti-ferroelectric characteristics. Providing the microscopic insights of
strain-induced crystal phase transformations, we propose a physics-based model
that shows good agreement with experimental results for 10 nm Hf<sub>1-x</sub>Z<sub>x</sub>O<sub>2</sub>.
Further, in a heterogeneous system, ferroelectric materials can exhibit
negative capacitance (NC) behavior. Such NC effects may lead to differential
amplification in local potential and can provide an enhanced charge and
capacitance response for the whole system compared to their constituents. Such
intriguing implications of NC phenomena have prompted the design and
exploration of many ferroelectric-based electronic devices to not only achieve
an improved performance but potentially also overcome some fundamental limits
of standard transistors. However, the microscopic physical origin as well as
the true nature of the NC effect, and direct experimental evidence remain
elusive and debatable. To that end, in this work, we systematically investigate
the underlying physical mechanism of the NC effect in the ferroelectric
material. Based upon the fundamental physics of ferroelectric material, we investigate
different assumptions, conditions, and distinct features of the quasi-static NC
effect in the single-domain and multi-domain scenarios. While the quasi-static
and hysteresis-free NC effect was initially propounded in the context of a single-domain
scenario, we highlight that the similar effects can be observed in multi-domain
FEs with soft domain-wall (DW) displacement. Furthermore, to obtain the
soft-DW, the gradient energy coefficient of the FE material is required to be
higher as well as the ferroelectric thickness is required to be lower than some
critical values. Otherwise, the DW becomes hard, and their displacement would
lead to hysteretic NC effects. In addition to the quasi-static NC, we discuss
different mechanisms that can lead to the transient NC effects. Furthermore, we
provide guidelines for new experiments that can potentially provide new
insights on unveiling the real origin of NC phenomena.</p>
<p> </p>
<p>Utilizing such ferroelectric insulators at the gate stack of
a transistor, ferroelectric-field-effect transistors (FeFETs) have been
demonstrated to exhibit both non-volatile memory and steep-slope logic
functionalities. To investigate such diverse attributes and to enable
application drive optimization of FeFETs, we develop a phase-field simulation
framework of FeFETs by self-consistently solving the time-dependent
Ginzburg-Landau (TDGL) equation, Poisson’s equation, and non-equilibrium
Green’s function (NEGF) based semiconductor charge-transport equation.
Considering HZO as the FE layer, we first analyze the dependence of the multi-domain
patterns on the HZO thickness (<i>T<sub>FE</sub></i>) and their critical role
in dictating the steep-switching (both in the negative and positive capacitance
regimes) and non-volatile characteristics of FeFETs. In particular, we analyze
the <i>T<sub>FE</sub></i>-dependent formation of hard and soft domain-walls
(DW). We show that, <i>T<sub>FE</sub></i> scaling first leads to an increase in
the domain density in the hard DW-regime, followed by soft DW formation and
finally polarization collapse. For hard-DWs, we describe the polarization
switching mechanisms and how the domain density impacts key parameters such as
coercive voltage, remanent polarization, effective permittivity and memory
window. We also discuss the enhanced but positive permittivity effects in
densely pattern multi-domain states in the absence of hard-DW displacement and
its implication in non-hysteretic attributes of FeFETs. For soft-DWs, we
present how DW-displacement can lead to effective negative capacitance in
FeFETs, resulting in a steeper switching slope and superior scalability. In
addition, we also develop a Preisach based circuit compatible model for FeFET
(and antiferroelectric-FET) that captures the multi-domain polarization
switching effects in the FE layer. </p>
<p> </p>
Unlike semiconductor
insulators (e.g., HZO), there are ferroelectric materials that exhibit a
considerably low bandgap (< 2eV) and hence, display semiconducting
properties. In this regard, non-perovskite-based 2D ferroelectric
-In<sub>2</sub>Se<sub>3</sub> shows a bandgap of ~1.4eV and that
suggests a combined ferroelectricity and semiconductivity in the same material
system. As part of this work, we explore the modeling and operational principle
of ferroelectric semiconductor metal junction (FeSMJ) based devices in the
context of non-volatile memory (NVM) application. First, we analyze the
semiconducting and ferroelectric properties of the α-In<sub>2</sub>Se<sub>3</sub> van
der Waals (vdW) stack via experimental characterization and first-principles
simulations. Then, we develop a FeSMJ device simulation framework by
self-consistently solving the Landau–Ginzburg–Devonshire equation, Poisson's
equation, and charge-transport equations. Our simulation results show good
agreement with the experimental characteristics of α-In<sub>2</sub>Se<sub>3</sub>-based
FeSMJ suggesting that the FeS polarization-dependent modulation of Schottky
barrier heights of FeSMJ plays a key role in providing the NVM functionality.
Moreover, we show that the thickness scaling of FeS leads to a reduction in
read/write voltage and an increase in distinguishability. Array-level analysis
of FeSMJ NVM suggests a lower read-time and read-write energy with respect to
the HfO<sub>2</sub>-based ferroelectric insulator tunnel junction (FTJ)
signifying its potential for energy-efficient and high-density NVM applications.
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Preliminary Validation Of Handheld X-ray Fluorescence (hhxrf) Spectrometry: Distinguishing Osseous And Dental Tissue From Non-bone Material Of Similar Chemical CompositionZimmerman, Heather 01 January 2013 (has links)
Forensic anthropologists normally examine bone from a variety of medicolegal contexts. The skeletal remains may in some cases be highly fragmented or taphonomically modified, making it difficult to sort bone from non-bone material. In these cases, the forensic anthropologist may rely on microscopic or destructive chemical analyses to sort the material. However, these techniques are costly and time-intensive, prompting the use of nondestructive analytical methods in distinguishing bone and teeth from non-bone materials in a limited number of cases. The proposed analytical techniques are limited in that they rely on an examination of the major elements in the material, and do not sort out all materials with a similar chemical composition to bone/teeth. To date, no methods have been proposed for the use of handheld Xray fluorescence (HHXRF) spectrometry in discriminating human and nonhuman bone/teeth from non-bone materials. The purpose of this research was to develop a method for the use of HHXRF spectrometry in forensic anthropology specifically related to distinguishing human and nonhuman bone and teeth from non-bone materials of a similar chemical composition using multivariate statistical analyses: principal components analysis (PCA), linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), and hierarchical cluster analysis (HCA). This was accomplished in two phases. Phase 1 consisted of a Reliability Test and involved sampling a single human long bone in thirty locations. Multiple spectra were collected at each location to examine the reliability of the instrument in detecting the elements both within a single site and between multiple sites. The results of the Reliability Test indicated that HHXRF consistently detected the major and minor elements found on the surface of a human bone. iv These results were used for Phase 2, designated the Accuracy Test, which involved analyzing a set of materials compiled from the literature to test the accuracy of the technique in discriminating bone (human and nonhuman) and non-bone samples (other biological and nonbiological). The results of the Accuracy Test indicate that osseous and dental tissue can be distinguished from non-bone material of similar chemical composition with a high degree of accuracy (94%) when data is collected from several locations on a sample and analyzed separately during multivariate statistical analyses. Overall, it was not possible to discriminate rock apatite and synthetic hydroxyapatite (synthetic bone) from bone. However, this technique successfully discriminated other non-bone materials that are chemically similar to bone, such as ivory and octocoral, which previous methods focusing on only a comparison of Ca/P ratios were unable to distinguish from bone.
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Determination and Speciation of Arsenic in Environmental and Biological SamplesBerg, Tiffany 01 September 2012 (has links)
A method was developed for the determination of total arsenic in rice grain by microwave-assisted digestion inductively coupled plasma mass spectrometry. Standard calibration solutions were matrix-matched with respect to acid concentration and carbon content post-digest. The importance of eliminating the drying step during sample preparation procedures was investigated. The method was validated with spikes containing standard arsenate solutions into the rice matrix, and with certified reference material SRM1568a (rice flour) from NIST. The method was successfully applied to a commercially available rice sample. Four arsenic species [arsenate (As(V)), arsenite (As(III)), dimethylarsinic acid (DMA) and monomethylarsonic acid (MMA)] were extracted from rice grains by microwave-assisted extraction and separated with high performance liquid chromatography inductively coupled plasma mass spectrometry. The method includes a novel sample clean-up step involving a dialysis procedure to decrease the amount of large starch molecules in the injection solution, in order to minimize poor resolution of chromatographic peaks and maximize column life. The method was validated with spikes of standard arsenic solutions, added to the rice matrix before the extraction procedure. Literature reference values for arsenic species quantification in SRM1568a (rice flour) were also compared. This method was successfully applied to a commercially available rice sample. A study into improvements in reverse phase-HPLC separations of arsenic species was conducted. For the first time, a Sunfire C8 column from Waters (Milford, CT) was employed for the separation of arsenic species in rice extracts. This column was compared to a Symmetry C8 column with respect to total elution time, detection limits, interference effects, and column life, and evaluated with respect to peak resolution, shifts in retention times, and peak symmetry.
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Chemical Approach to Tire Mark AnalysisLucchi, John 01 January 2023 (has links) (PDF)
Fatal accidents on the road are an unfortunate daily occurrence, with almost 30,000 deaths resulting from hit-and-runs in the USA between 2006 and 2021. The identification of the driver responsible for this road crime can become a challenge. Nonetheless, the accident scene provides a large amount of trace evidence that can prove critical to this matter, one of them being the tire marks. While traditional tire mark analysis is full of physical information helping the reconstruction of the event, additional information can be extracted from the rubber left during the braking event. Each tire model is manufactured with a specific design, obtained by a chemical formulation that can become its signature. Supplemental to the molecular profile of the rubber itself, analysis of the trace and contaminant elements can help build the chemical signature for the tire rubber. This work consists of establishing the link between the tire and the skid mark and particles it left during a braking event.
The difference between tire models was proved from the elemental analysis of the tire rubber itself, showing that the specific content of minor and trace elements is specific to the model. Expanding to the problem of tire marks, the first challenge consists in efficiently sampling the rubber from the road. The development of an effective procedure to lift the tire particles from the mark is demonstrated in this work. This does present some challenges, including removal of other particles present within the lift and extraction of the tire rubber for further analysis by ICP-MS, providing an elemental profile for the sampled skid mark. Finally, with the skid mark rubber analyzed, it is compared with the elemental profile of the rubber from the source tire. The results of this comparison will be discussed in both simulated (with a lab- made tire mark maker) and field cases (from braking tests performed by the Florida Highway Patrol (FHP)).
The results of my research provide the forensic community with the first evaluation of elemental analysis of tire rubber to use this seldom used trace evidence, all along the analytical process, from sampling to analysis to attribution.
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Study of Reaction Kinetics for Elemental Mercury Vapor Oxidation for Mercury Emission ControlSriram, Vishnu January 2017 (has links)
No description available.
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ELEMENTAL SPECIATION BY CHROMATOGRAPHIC SEPARATIONS INTERFACED TO INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRYPAWLECKI-VONDERHEIDE, ANNE MARIE 01 July 2003 (has links)
No description available.
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TRACE ELEMENTAL SPECIATION USING CHROMATOGRAPHY/CAPILLARY ELECTROPHORESIS COUPLED TO INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY FOR FOOD, PHARMACEUTICAL AND ENVIRONMENTAL ANALYSISKANNAMKUMARATH, SASI S. 01 July 2004 (has links)
No description available.
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INTERPRETATION OF MASS SPECTRA FOR ELEMENTAL SPECIATION STUDIESMEIJA, JURIS 13 July 2005 (has links)
No description available.
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