Radioanalytical multi-elemental analysis : new methodology and archaeometric applications

Title from PDF of title page (University of Missouri--Columbia, viewed on October 21, 2010).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. J. David Robertson.Vita.Ph. D. University of Missouri--Columbia 2010.Several projects are covered in this dissertation: the application of instrumental neutron activation analysis (INAA) and rigorous statistical analyses to the sourcing of Egyptian limestone and Kenyan obsidian, and the development of a method to determine titanium, barium, and arsenic concentrations in obsidian using epithermal neutron activation. INAA, when coupled with rigorous statistical methods, including principal component analysis and clustering techniques, can provide the precision and confidence needed to accurately determine the source of material. However, this technique has not been fully explored for the provenancing of Egyptian limestone sculpture. A combination of the elemental concentration data and rigorous statistical methods is used to study the compositional differences between known ancient quarries. Obsidian is an important component of East African artifacts. Although compositional studies of obsidian from East Africa conducted in the 1980s showed great potential, a comprehensive database has not been developed. Here, samples from Kenya were examined via INAA. The results indicate that there is a clear correlation between geographic proximity and chemical composition. Titanium and barium are often used for characterizing obsidian, especially in areas in Africa. A method has been developed to analyze for these elements using epithermal neutron activation analysis, which takes advantage of larger natural abundances of parent nuclides and a higher probability for epithermal neutron reactions. It produces results with improved accuracy and precision for titanium and barium analyses in obsidian. It is also now possible to analyze for arsenic, which has not previously been reported in obsidian studies.Includes bibliographical reference

Electron degeneracy and intrinsic magnetic properties of epitaxial Nb:SrTiO3_3 thin-films controlled by defects

We report thermoelectric power experiments in e-doped thin films of SrTiO$_3$ (STO) which demonstrate that the electronic band degeneracy can be lifted through defect management during growth. We show that even small amounts of cationic vacancies, combined with epitaxial stress, produce a homogeneous tetragonal distortion of the films, resulting in a Kondo-like resistance upturn at low temperature, large anisotropic magnetoresistance, and non-linear Hall effect. Ab-initio calculations confirm a different occupation of each band depending on the degree of tetragonal distortion. The phenomenology reported in this paper for tetragonally distorted e-doped STO thin films, is similarto that observed in LaAlO$_3$/STO interfaces and magnetic STO quantum wells.Comment: 5 pages, 5 figure

X-ray Fluorescence and Neutron Activation Analysis of Obsidian from the Red Sea Coast of Eritrea

The strategic location of Eritrea along the Red Sea coast and the Horn of Africa makes it an important place to study human prehistory over a long span of time. However, recurrent political instability and the environmental adversity in the region have hindered comprehensive archaeological investigation. Paleolithic research in Eritrea began after the country obtained independence from Ethiopia in 1991. Geological survey in the Abdur area, along the Gulf of Zula coast (Figure 1), identified Paleolithic artifacts embedded in reef limestone dating to ~ 125 Ka BP (Walter et al., 2000). Based on this evidence, human coastal adaptation during the Late Pleistocene has been proposed. To explore the archaeological potential of the region, surveys and excavations were recently initiated along the Gulf of Zula and Buri Peninsula portions of the Red Sea coast. The survey documented a series of prehistoric sites from coastal and inland contexts featuring Acheulian, Middle Stone Age (MSA) and Later Stone Age (LSA) artifacts (Beyin and Shea, 2007). The Acheulian and MSA Lithic assemblages include highly deflated surface scatters of handaxes, prepared core products and retouched points made on locally available materials such as basalt, shale, and rhyolite. These assemblages however, lack secured stratigraphic contexts and obtaining radiometric dating is problematical. Excavations at three sites, Asfet, Misse East and Gelalo NW (Figure 1) in 2006 produced archaeological deposits of LSA affinity with mollusk shell association. A large quantity of debitage, blades, bladelets, backed tools and microliths characterize the lithic artifacts. A few of the artifacts are shown in Figure 2. The LSA bearing archaeological strata have been dated to the Early Holocene by 14C (AMS)

Quantitative parameters for the examination of InGaN QW multilayers by low-loss EELS

We present a detailed examination of a multiple InxGa1-xN quantum well (QW) structure for optoelectronic applications. The characterization is carried out using scanning transmission electron microscopy (STEM), combining high-angle annular dark field (HAADF) imaging and electron energy loss spectroscopy (EELS). Fluctuations in the QW thickness and composition are observed in atomic resolution images. The impact of these small changes on the electronic properties of the semiconductor material is measured through spatially localized low-loss EELS, obtaining band gap and plasmon energy values. Because of the small size of the InGaN QW layers additional effects hinder the analysis. Hence, additional parameters were explored, which can be assessed using the same EELS data and give further information. For instance, plasmon width was studied using a model-based fit approach to the plasmon peak; observing a broadening of this peak can be related to the chemical and structural inhomogeneity in the InGaN QW layers. Additionally, Kramers-Kronig analysis (KKA) was used to calculate the complex dielectric function (CDF) from the EELS spectrum images (SIs). After this analysis, the electron effective mass and the sample absolute thickness were obtained, and an alternative method for the assessment of plasmon energy was demonstrated. Also after KKA, the normalization of the energy-loss spectrum allows us to analyze the Ga 3d transition, which provides additional chemical information at great spatial resolution. Each one of these methods is presented in this work together with a critical discussion of their advantages and drawbacks

Circulating miR-181 is a prognostic biomarker for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a relentless neurodegenerative disease of the human motor neuron system, where variability in progression rate limits clinical trial efficacy. Therefore, better prognostication will facilitate therapeutic progress. In this study, we investigated the potential of plasma cell-free microRNAs (miRNAs) as ALS prognostication biomarkers in 252 patients with detailed clinical phenotyping. First, we identified, in a longitudinal cohort, miRNAs whose plasma levels remain stable over the course of disease. Next, we showed that high levels of miR-181, a miRNA enriched in neurons, predicts a greater than two-fold risk of death in independent discovery and replication cohorts (126 and 122 patients, respectively). miR-181 performance is similar to neurofilament light chain (NfL), and when combined together, miR-181 + NfL establish a novel RNA–protein biomarker pair with superior prognostication capacity. Therefore, plasma miR-181 alone and a novel miRNA–protein biomarker approach, based on miR-181 + NfL, boost precision of patient stratification. miR-181-based ALS biomarkers encourage additional validation and might enhance the power of clinical trials

Potassium fertilization: paradox or K management dilemma?

In 2014, Khan et al. presented evidence that soil exchangeable K (Exch-K) increases over time without addition of potassium (K) to the soil despite the removal of K in crops on a soil rich in montmorillonite and illite. The authors term this behavior ‘The potassium paradox’. From their review of the literature, the authors also report a lack of crop response to potassium chloride (KCl) fertilization. Close evaluation of these findings reveals that their observations can be interpreted and predicted using current knowledge of K in soil chemistry and its uptake by plants, and there is no paradox in K behavior in the soil–plant system. There is also no evidence of a detrimental effect of KCl on crop yield or quality. Their conclusion that the widely used Exch-K soil test is inadequate for managing K fertilization is discussed and some possible modifications to improve its performance are included. We believe that measurement of Exch-K is an essential and valuable tool and its use should be continued, along with improvements in recommending K fertilizer application

Report on a Retroperitoneal Teratoma (Foetus in foetu)

Successful removal of a retroperitoneal teratoma from an infant is described. Various theories dealing with the origin of such tumors are discussed. Blood supply, hemopoiesis and circulation of the tumor have been investigated

Critical magnetic behavior in [Ag8/Co0.5]x64, [Ag8/Co1]x32 and [Ag16/Co1]x32 epitaxial multilayers

We investigate the low temperature magnetic behavior of three epitaxial Co/Ag multilayers, grown onto MgO (001) substrates, with a nominal content per period of either half a monolayer or one monolayer of Co, and either 8 or 16 Ag monolayers. The samples were studied by X-ray reflectivity and diffraction, transmission electron microscopy, magnetometry and ac susceptometry. The results indicated a well defined stacking sequence in the growth direction, the number of periods and of Ag monolayers per period being coincident with the nominal values for each sample. The Co layers were found to be discontinuous and corresponded to a quasi-monodisperse in-plane distribution of Co nanoparticles embedded in a Ag(001) matrix. The zero-field cooled and field cooled temperature variations of the low field magnetization indicated the presence of irreversibilities at temperatures below 20 K. The ac field frequency (f) and temperature (T) dependencies of the real part of the susceptibility (¿') corresponded to a Vogel-Fulcher behavior in the three samples, and indicated a frequency shift parameter (G) of the order of 4 x 10-2. For each sample, the experimental data corresponding to the variations of the imaginary part of the ac susceptibility (¿¿) with f and T were found to collapse into a single curve according to the dynamic scaling law. Taken together, these results allow us to conclude that the three multilayers experience a phase transition of the paramagnetic to superspin glass type, driven by the dipolar interactions between the Co nanoparticles. Regarding the influence of the multilayer features, we found a clear dependence of the order parameter of the transition on the nominal number of Co monolayers per period

Emerging Diluted Ferromagnetism in High-T-c Superconductors Driven by Point Defect Clusters

Defects in ceramic materials are generally seen as detrimental to their functionality and applicability. Yet, in some complex oxides, defects present an opportunity to enhance some of their properties or even lead to the discovery of exciting physics, particularly in the presence of strong correlations. A paradigmatic case is the high-temperature superconductor YBa2Cu3O7-delta(Y123), in which nanoscale defects play an important role as they can immobilize quantized magnetic flux vortices. Here previously unforeseen point defects buried in Y123 thin films that lead to the formation of ferromagnetic clusters embedded within the superconductor are unveiled. Aberration-corrected scanning transmission microscopy has been used for exploring, on a single unit-cell level, the structure and chemistry resulting from these complex point defects, along with density functional theory calculations, for providing new insights about their nature including an unexpected defect-driven ferromagnetism, and X-ray magnetic circular dichroism for bearing evidence of Cu magnetic moments that align ferromagnetically even below the superconducting critical temperature to form a dilute system of magnetic clusters associated with the point defects

The Threat of Capital Drain: A Rationale for Public Banks?

This paper yields a rationale for why subsidized public banks may be desirable from a regional perspective in a financially integrated economy. We present a model with credit rationing and heterogeneous regions in which public banks prevent a capital drain from poorer to richer regions by subsidizing local depositors, for example, through a public guarantee. Under some conditions, cooperative banks can perform the same function without any subsidization; however, they may be crowded out by public banks. We also discuss the impact of the political structure on the emergence of public banks in a political-economy setting and the role of interregional mobility