Influence Of Radiation And Multivalent Cation Additions On Phase Separation And Crystallization Of Glass

The major objectives of this proposed investigation are as follows: (1) To investigate the influence of multivalent cations on the thermodynamics and kinetics of phase separation and crystallization in simple model glasses. (2) To study the influence of a and b particle, heavy ion bombardment and g irradiation on phase separation and crystallization in simple model glasses. (3) To examine the structural changes produced by radiation just prior to the onset of phase separation and/or crystallization. (4) To develop models to explain the observed effects of multivalent cations and radiation on phase separation and crystallization. (5) To utilize the results of these experimental and modeling studies to provide guidelines for the allowed range of composition choices and processing conditions in order to avoid the formation of unwanted phases in nuclear waste disposal glasses

Genetic Variants For Head Size Share Genes and Pathways With Cancer

The size of the human head is highly heritable, but genetic drivers of its variation within the general population remain unmapped. We perform a genome-wide association study on head size (N = 80,890) and identify 67 genetic loci, of which 50 are novel. Neuroimaging studies show that 17 variants affect specific brain areas, but most have widespread effects. Gene set enrichment is observed for various cancers and the p53, Wnt, and ErbB signaling pathways. Genes harboring lead variants are enriched for macrocephaly syndrome genes (37-fold) and high-fidelity cancer genes (9-fold), which is not seen for human height variants. Head size variants are also near genes preferentially expressed in intermediate progenitor cells, neural cells linked to evolutionary brain expansion. Our results indicate that genes regulating early brain and cranial growth incline to neoplasia later in life, irrespective of height. This warrants investigation of clinical implications of the link between head size and cancer

Global patterns of sex- and age-specific variation in seabird bycatch

Fisheries bycatch is a major threat to seabird populations, and understanding sex- and age-biases in bycatch rates is important for assessing population-level impacts. We analysed 44 studies to provide the first global assessment of seabird bycatch by sex and age, and used generalised models to investigate the effects of region and fishing method. Bycatch was highly biased by sex (65% of 123 samples) and age (92% of 114 samples), with the majority of samples skewed towards males and adults. Bycatch of adults and males was higher in subpolar regions, whereas there was a tendency for more immatures and females to be killed in subtropical waters. Fishing method influenced sex- and age-ratios only in subpolar regions. Sex- and age-biases are therefore common features of seabird bycatch in global fisheries that appear to be associated largely with differences in at-sea distributions. This unbalanced mortality influences the extent to which populations are impacted by fisheries, which is a key consideration for at-risk species. We recommend that researchers track individuals of different sex and age classes to improve knowledge of their distribution, relative overlap with vessels, and hence susceptibility to bycatch. This information should then be incorporated in ecological risk assessments of effects of fisheries on vulnerable species. Additionally, data on sex, age and provenance of bycaught birds should be collected by fisheries observers in order to identify regions and fleets where bycatch is more likely to result in population-level impacts, and to improve targeting of bycatch mitigation and monitoring of compliance

Frost Heave in Soils : The Influence of particles on Solidification

International Conference on Low Temperature Science. I. Conference on Physics of Snow and Ice, II. Conference on Cryobiology. (August, 14-19, 1966, Sapporo, Japan

The influence of radiation and multivalent cation additions on phase separation and crystallization of glass. 1998 annual progress report

'The major objectives of this proposed investigation are as follows: (1) To investigate the influence of multivalent cations on the thermodynamics and kinetics of phase separationand crystallization in simple model glasses. (2) To study the influence of a and b particle, heavy ion bombardment and g irradiation on phase separation and crystallization in simple model glasses. (3) To examine the structural changes produced by radiation just prior to the onset of phase separation and/or crystallization. (4) To develop models to explain the observed effects of multivalent cations and radiation on phase separation and crystallization. (5) To utilize the results of these experimental and modeling studies to provide guidelines for the allowed range of composition choices and processing conditions in order to avoid the formation of unwanted phases in nuclear waste disposal glasses. At the fundamental level, the effects of radiation, of transition metal ion additions, and of melting history in the case of multi-valent cations, on phase separation and crystallization behavior will be evaluated for simple glasses whose baseline behavior is characterized and understood. At the practical level, the program will determine the magnitude of the risk associated with the effects of radiation in inducing phase separation and crystallization. It will also provide approaches to ameliorating such effects through controlled complementary dopants and control of melting/processing conditions.

Influence of Radiation and Multivalent Cation Additions on Phase Separation and Crystallization of Glass

This report presents results of: (1) measurement of valence state ratios of iron in glass, and (2) a study of the effect of iron redox ratio on phase separation behavior in a glass. The redox ratio of iron in two sodium silicate (NS) glasses has been determined using a colorimetric method, Moessbauer analysis, and optical absorption. The experimental procedures were described in a previous report. We found that these three methods gave excellent agreement for the values of the Fe++/Fe+++ (redox ratio) in the glasses. Also, using the results of the colorimetric analysis we were able to find the extinction coefficients for the18.56% NS and the 13% NS glasses. We have utilized the optical absorption data that was taken for purposes of determining redox ratios to provide glass structural information. In particular, it has been suggested that the band centered near 14,500 cm-1 is indicative of Fe2+ - O2- - Fe3+ formation. In addition, the relative band intensities at 10,000 cm-1 and 4,800 cm-1 could give us information as to the environment around the Fe2+ responsible for the 4,800 cm-1 band. The Moessbauer data will provide supporting structural information. For example, the relative number of clustered and free ferric ions can be computed from the ratio of areas under the doublet and sextet in the liquid He spectra. Also, the change in shift parameter with redox ratio will provide an indication of whether there is an increase or decrease in tetrahedral site symmetry about both ferrous and ferric ions. Finally, the quadrupole splitting parameter provides information regarding the site symmetries about the Fe++ and Fe+++. Currently, we are analyzing the spectral data for these purposes. The Moessbauer work was done in conjunction with colleagues at PNNL, and a manuscript is currently in preparation. The effect of oxidation state of iron on the phase separation of xNa2O {center_dot}(100-x)SiO2 glasses, x = 18.56 and 13, containing 0.5 mole % iron oxide was studied. The oxidation state of iron in the glasses was varied by changing the melting conditions such as melting temperature and melting atmosphere. The oxidation states of the iron ion were determined by the colorimetric method and by the UV-VIS NIR spectrophotometric method, and a comparison was made between the results obtained using these two techniques. Immiscibility temperatures of the glasses were determined by opalescence and clearing methods. The immiscibility temperature of the sodium silicate binary glasses decreased approximately 25 C with the addition of 0.5 mole % Fe2O3. The immiscibility temperature of the doped glasses increased slightly with increasing concentration of Fe2+ ion in the glass. The liquidus temperature of the 18.56 NS2 glass was determined using an X-ray diffraction technique. Approximately 3 grams of glass powder were heated for 4 hours in the temperature region near the liquidus temperature. XRD patterns were obtained from the samples to determine if any crystalline material was present. The heat-treatment temperatures were incremented in 2 C intervals, and the liquidus temperature was taken as the minimum heat-treatment temperature where the crystalline XRD peaks disappeared in the XRD pattern. From this analysis is was determined that the liquidus temperature decreased about 26 C by the addition of 0.5 mole % Fe2O3. The prediction of immiscibility tendency upon the addition of a minor amount of third component was made using models proposed by Tomozawa and Obara and Nakagawa and Izumitani. Tomozawa and Obara's model showed good agreement with the measured immiscibility values