We optical and electrical properties of titanium dioxide

This thesis describes the investigation of shallow and deep trap states in single crystal rutile end commercial pigments. The processes involved when rutile acts as a photocatalyst are examined and their relevance to the pigment industry is discussed. Single crystals have been grown by the plasma flame fusion method. Oxidised (colourless) and reduced (blue) crystals were grown by altering the position of the growth pedestal relative to the plasma. Crystals doped with aluminum, niobium, manganese and iron introduced via the powder feed material were successfully grown as single crystals. The techniques of photoconductivity, photoluminascene, photon stimulated current, thermally stimulated conductivity (TSC) and thexmoluminescene (TL) have been used to probe deep and shallow levels in the single crystal rutile. The kinetic responses of PL and PC have been explained consistently in terms of a charge transfer model by considering the hole traffic through the luminescence centre as well as the electron concentration in the conduction band, and realising that the Cr(^3+) luminescence centre is only one of the many recombination centres present in these crystals, A study of TSC and TL in the nominally 'undoped' single crystals reveals the presence of six discrete electron trapping levels. The TSC and TL curves are analysed and consistent values of the trapping parameters are obtained. Limitations of the simple insulator model and its application to single crystal rutile are discussed. Crystals from different sources all contain the same three trapping levels with ionisation energies of 0.1), 0.24 and 0o37 eV. The density of these traps increase as the crystals are chemically reduced. An investigation of manganese, chromium, iron, cobalt and nickel diffusion doped single crystal rutile reveals the presence of the 0,19 eV trap in chromium doped crystals and the 0.41 eV trap in nickel, chromium, iron and cobalt doped crystals

Magnetostratigraphy of the Koobi Fora Formation, Lake Turkana, Kenya

Journal ArticleThe Koobi Fora Formation, a Pliocene and Pleistocene sequence of sedimentary deposits northeast of Lake Turkana, has yielded numerous fossils and stone artifacts of early hominids. Stratigraphic correlation of the hominid-bearing deposits throughout the Turkana region was established primarily by the chemistry and isotopic ages of volcanic tuffs and complemented by magnetostratigraphic studies. We have reinterpreted previously published magnetostratigraphy from the upper part of the Koobi Fora Formation because the original stratigraphy and dating of tuffs have been revised. In our reinterpretation we include previously unpublished data from the uppermost part of the formation. The upper magnetozones correlate with parts of the Brunhes Normal-Polarity Chron and Matuyama Re versed-Polarity Chron (about 0.6-0.85 Ma) and are separated from the magnetozones of the upper part of the Matuyama (2.0-1.25 Ma) by a disconformity. The Olduvai Normal-Polarity Subchron is represented within the Matuyama, but the lower part of the Matuyama (2.4-2.0 Ma) is missing due to an erosional disconformity. We have also determined magnetozones in the lower part of the Koobi Fora Formation, which had not been sampled for paleomagnetism during the earlier studies. Our time calibration of the magnetozones is made possible by isotopic dating of several tuffs and by chemical correlation of Koobi Fora tuffs with dated tuffs in the Shungura Formation of southern Ethiopia. The tephra correlations are corroborated by the excellent concordance between the magnetostratigraphies of the Koobi Fora and Shungura formations. The lower part of the Koobi Fora spans the interval from about 4 Ma to 2.4 Ma, within the Gilbert Re versed-Polarity and Gauss Normal-Polarity chrons. Rock magnetic studies indicate that detrital magnetite carries most of the stable remanence, although hematite contributes to the remanence as indicated by thermal demagnetization. The hematite, which presumably formed by postdepositional oxidation of original iron oxide grains, carries chemical remanent magnetization (CRM) that diminishes the sharpness of polarity zone boundaries. The CRM accumulated continuously within the uppermost 10 m of sediment below the land surface, so that the CRM reinforces the depositional remanent magnetization within thick magnetozones but obscures magnetozones having durations of roughly less than 70,000 years in sections where the sedimentation rate was approximately 15 cm/1000 years

Corticotropin-releasing factor receptors couple to multiple g-proteins to activate diverse intracellular signaling pathways in mouse hippocampus: role in neuronal excitability and associative learning

Corticotropin-releasing factor (CRF) exerts a key neuroregulatory control on stress responses in various regions of the mammalian brain, including the hippocampus. Using hippocampal slices, extracts, and whole animals, we investigated the effects of human/rat CRF (h/rCRF) on hippocampal neuronal excitability and hippocampus-dependent learning in two mouse inbred strains, BALB/c and C57BL/6N. Intracellular recordings from slices revealed that application of h/rCRF increased the neuronal activity in both mouse inbred strains. Inhibition of protein kinase C (PKC) by bisindolylmaleimide I (BIS-I) prevented the h/rCRF effect only in hippocampal slices from BALB/c mice but not in slices from C57BL/6N mice. Inhibition of cAMP-dependent protein kinase (PKA) by H-89 abolished the h/rCRF effect in slices from C57BL/6N mice, with no effect in slices from BALB/c mice. Accordingly, h/rCRF elevated PKA activity in hippocampal slices from C57BL/6N mice but increased only PKC activity in the hippocampus of BALB/c mice. These differences in h/rCRF signal transduction were also observed in hippocampal membrane suspensions from both mouse strains. In BALB/c mice, hippocampal CRF receptors coupled to Gq/11 during stimulation by h/rCRF, whereas they coupled to Gs, Gq/11, and Gi in C57BL/6N mice. As expected on the basis of the slice experiments, h/rCRF improved context-dependent fear conditioning of BALB/c mice in behavioral experiments, and BIS-I prevented this effect. However, although h/rCRF increased neuronal spiking in slices from C57BL/6N mice, it did not enhance conditioned fear. These results indicate that the CRF system activates different intracellular signaling pathways in mouse hippocampus and may have distinct effects on associative learning depending on the mouse strain investigated

Nationwide Analysis on Intentional Indoor and Outdoor Tanning: Prevalence and Correlates

Outdoor and indoor tanning are considered as risk factors for the development of skin cancer. The aims of this nationwide representative study were to quantify both behaviors in a sample with a wide age range, to identify those showing both behaviors and to explore and compare determinants of both behaviors. We used data from the fifth wave (2019) of the National Cancer Aid Monitoring (NCAM). We surveyed the representative sample including 4000 individuals, aged 16-65 years, living in Germany. Data were collected through telephone interviews. In addition to descriptive statistics, we used logistic regression analyses to identify determinants. The one-year-prevalence of tanning bed use was 7.5%, while 31.9% tanned (very) often intentionally outdoors in at least one situation (weekdays, holidays, and weekends). A total of 3.2% reported both risk behaviors. Regression analyses revealed that tanning bed use is associated with employment, an increased number of naevi, and lack of risk awareness. Intentional outdoor tanning was associated with male sex, younger age, past tobacco use, and low risk awareness of UV radiation. Our findings suggest that only a minority of subjects showed both risk behaviors. This implies that individuals seem to perform either one behavior or the other. In addition, the associated determinants differed between both behaviors, implying that specific preventive measures tailored to address to each tanning behavior are needed

Fabrication of continuous mesoporous carbon films with face-centered orthorhombic symmetry through a soft templating pathway

Preparation of well-ordered continuous mesoporous carbon films without the use of an intermediate inorganic template was achieved by spin coating of a thermosetting phenolic resin, resorcinol/phloroglucinol/formaldehyde, and a thermally-decomposable organic template, Pluronic F127 (PEO106–PPO70–PEO106). The carbon films were deposited onto silicon, platinum/silicon, copper, glass, and quartz substrates. Afterwards, decomposition of the organic template and solidification of the carbon precursors are simultaneously performed through a carbonization process. The resulting films referred to as CKU-F69, are (010)-oriented, and possess a face-centered orthorhombic Fmmm symmetry. Film periodicity is maintained even after a 68% uniaxial contraction perpendicular to the substrate brought on by carbonization at 800 °C. This method could facilitate the mass-production and creation of new carbon and carbon–polymer porous films that find broad potential applications in catalysis, separation, hydrogen storage, bioengineering, nanodevices, and nanotemplates

An 8.22 Mb Assembly and Annotation of the Alpaca (Vicugna pacos) Y Chromosome.

The unique evolutionary dynamics and complex structure make the Y chromosome the most diverse and least understood region in the mammalian genome, despite its undisputable role in sex determination, development, and male fertility. Here we present the first contig-level annotated draft assembly for the alpaca (Vicugna pacos) Y chromosome based on hybrid assembly of short- and long-read sequence data of flow-sorted Y. The latter was also used for cDNA selection providing Y-enriched testis transcriptome for annotation. The final assembly of 8.22 Mb comprised 4.5 Mb of male specific Y (MSY) and 3.7 Mb of the pseudoautosomal region. In MSY, we annotated 15 X-degenerate genes and two novel transcripts, but no transposed sequences. Two MSY genes, HSFY and RBMY, are multicopy. The pseudoautosomal boundary is located between SHROOM2 and HSFY. Comparative analysis shows that the small and cytogenetically distinct alpaca Y shares most of MSY sequences with the larger dromedary and Bactrian camel Y chromosomes. Most of alpaca X-degenerate genes are also shared with other mammalian MSYs, though WWC3Y is Y-specific only in alpaca/camels and the horse. The partial alpaca Y assembly is a starting point for further expansion and will have applications in the study of camelid populations and male biology

An 8.22 Mb Assembly and Annotation of the Alpaca (Vicugna pacos) Y Chromosome.

The unique evolutionary dynamics and complex structure make the Y chromosome the most diverse and least understood region in the mammalian genome, despite its undisputable role in sex determination, development, and male fertility. Here we present the first contig-level annotated draft assembly for the alpaca (Vicugna pacos) Y chromosome based on hybrid assembly of short- and long-read sequence data of flow-sorted Y. The latter was also used for cDNA selection providing Y-enriched testis transcriptome for annotation. The final assembly of 8.22 Mb comprised 4.5 Mb of male specific Y (MSY) and 3.7 Mb of the pseudoautosomal region. In MSY, we annotated 15 X-degenerate genes and two novel transcripts, but no transposed sequences. Two MSY genes, HSFY and RBMY, are multicopy. The pseudoautosomal boundary is located between SHROOM2 and HSFY. Comparative analysis shows that the small and cytogenetically distinct alpaca Y shares most of MSY sequences with the larger dromedary and Bactrian camel Y chromosomes. Most of alpaca X-degenerate genes are also shared with other mammalian MSYs, though WWC3Y is Y-specific only in alpaca/camels and the horse. The partial alpaca Y assembly is a starting point for further expansion and will have applications in the study of camelid populations and male biology

Solution-based synthesis of kesterite thin film semiconductors

Large-scale deployment of photovoltaic modules is required to power our renewable energy future. Kesterite, Cu2ZnSn(S, Se)4, is a p-type semiconductor absorber layer with a tunable bandgap consisting of earth abundant elements, and is seen as a potential 'drop-in' replacement to Cu(In,Ga)Se2 in thin film solar cells. Currently, the record light-to-electrical power conversion efficiency (PCE) of kesterite-based devices is 12.6%, for which the absorber layer has been solution-processed. This efficiency must be increased if kesterite technology is to help power the future. Therefore two questions arise: what is the best way to synthesize the film? And how to improve the device efficiency? Here, we focus on the first question from a solution-based synthesis perspective. The main strategy is to mix all the elements together initially and coat them on a surface, followed by annealing in a reactive chalcogen atmosphere to react, grow grains and sinter the film. The main difference between the methods presented here is how easily the solvent, ligands, and anions are removed. Impurities impair the ability to achieve high performance (>∼10% PCE) in kesterite devices. Hydrazine routes offer the least impurities, but have environmental and safety concerns associated with hydrazine. Aprotic and protic based molecular inks are environmentally friendlier and less toxic, but they require the removal of organic and halogen species associated with the solvent and precursors, which is challenging but possible. Nanoparticle routes consisting of kesterite (or binary chalcogenides) particles require the removal of stabilizing ligands from their surfaces. Electrodeposited layers contain few impurities but are sometimes difficult to make compositionally uniform over large areas, and for metal deposited layers, they have to go through several solid-state reaction steps to form kesterite. Hence, each method has distinct advantages and disadvantages. We review the state-of-the art of each and provide perspective on the different strategies.Fil: Todorov, I. T.. IBM Research. Thomas J. Watson Research Center; Estados UnidosFil: Hillhouse, H. W.. University of Washington; Estados UnidosFil: Aazou, S.. Mohammed V University; MarruecosFil: Sekkat, Z.. Mohammed V University; MarruecosFil: Vigil Galán, O.. National Polytechnic Institute; MéxicoFil: Deshmukh, S. D.. Purdue University; Estados UnidosFil: Agrawal, R.. Purdue University; Estados UnidosFil: Bourdais, S.. No especifíca;Fil: Valdes, Matias Hernan. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones en Ciencia y Tecnología de Materiales. Universidad Nacional de Mar del Plata. Facultad de Ingeniería. Instituto de Investigaciones en Ciencia y Tecnología de Materiales; ArgentinaFil: Arnou, P.. University Of Luxembourg; LuxemburgoFil: Mitzi, D.B.. University of Duke; Estados UnidosFil: Dale, P.. University Of Luxembourg; Luxemburg

Association of the 894G>T polymorphism in the endothelial nitric oxide synthase gene with risk of acute myocardial infarction

Background: This study was designed to investigate the association of the 894G>T polymorphism in the eNOS gene with risk of acute myocardial infarction (AMI), extent of coronary artery disease (CAD) on coronary angiography, and in-hospital mortality after AMI. Methods: We studied 1602 consecutive patients who were enrolled in the GEMIG study. The control group was comprised by 727 individuals, who were randomly selected from the general adult population. Results: The prevalence of the Asp298 variant of eNOS was not found to be significantly and independently associated with risk of AMI (RR = 1.08, 95%CI = 0.77–1.51, P = 0.663), extent of CAD on angiography (OR = 1.18, 95%CI = 0.63–2.23, P = 0.605) and in-hospital mortality (RR = 1.08, 95%CI = 0.29–4.04, P = 0.908). Conclusion: In contrast to previous reports, homozygosity for the Asp298 variant of the 894G>T polymorphism in the eNOS gene was not found to be associated with risk of AMI, extent of CAD and in-hospital mortality after AM