Apatite Control of Choncritic Actinide Chemistry?

The solar system Th/U is regarded as about 3.7, and ratios close to this are directly measured in a wide variety of planetary materials. Consequently, given that chondritic composition is regarded as solar for refractory lithophile elements, it is surprising that some ordinary chondrites show high ratios (6-6.5). We set out to understand the origin and implications of these anomalies, first by establishing that we had samples of the anomalous material using high accuracy isotope dilution, ICPMS measurements ofTh/U. Our three samples of Glatton (L6) were not anomalous (Th/U from 3.71 to 3.84), but for 12, typically gram-sized, samples of Harleton (L6) we find a range of Th/U from 2.5 to 6, a greater range of Th/U in one meteorite than in all previous ordinary chondrite analyses. Moreover, Fig. 1 shows (l) the Th/U variations linearly correlate with 11 U, suggesting two component mixing; (2) other literature analyses follow the Harleton trend

Petrology and geochemistry of the NWA 3368 Eucrite

We report the petrology and geochemistry of NWA 3368, a new non-cumulate, monomict eucrite breccia with a variety of clast sizes and a pink-tinted matrix. Analytical techniques include electron microprobe, INAA, and ICP-MS

Four Academic Years (P. P. Bazhov in the Yekaterinburg Diocesan Women’s College. August 1910 — November 1914)

На материалах Екатеринбургских епархиальных ведомостей реконструируется профессиональная биография П. П. Бажова с августа 1904 по ноябрь 1914 г.The professional biography of P. P. Bazhov from August 1910 to November 1914 is reconstructed in the article on the basis of the materials of Yekaterinburg Diocesan Gazette

Origin of Thorium/Uranium Variations in Carbonaceous Chondrites

Thorium-, U-, and Pb-isotopic analyses of a wide variety of planetary materials show that Th/U ratio (by weight) varies from 3.5 to 4.2. It is generally believed that chondritic meteorites contain refractory lithophile elements in a relative proportions close to solar, i.e., CI chondrites [1]. Surprisingly, a number of analyses of different types of carbonaceous chondrites show a large (at least a factor of 3) scatter in Th/U measurements [2]. The widest spread in Th/U is observed in the most primitive materials, CI-type chondrites. Cosmochronological models rely on the precise knowledge of the average solar system Th/U, therefore it is important to achieve a better understanding of the actinide chemistry in chondrites, e.g., what causes the variations in Th/U ratio

Thermal Alteration of Labile Elements in Carbonaceous Chondrites

Carbonaceous chondrite meteorites are some of the oldest Solar System planetary materials available for study. The CI group has bulk abundances of elements similar to those of the solar photosphere. Of particular interest in carbonaceous chondrite compositions are labile elements, which vaporize and mobilize efficiently during post-accretionary parent-body heating events. Thus, they can record low-temperature alteration events throughout asteroid evolution. However, the precise nature of labile-element mobilization in planetary materials is unknown. Here we characterize the thermally induced movements of the labile elements S, As, Se, Te, Cd, Sb, and Hg in carbonaceous chondrites by conducting experimental simulations of volatile-element mobilization during thermal metamorphism. This process results in appreciable loss of some elements at temperatures as low as 500 K. This work builds on previous laboratory heating experiments on primitive meteorites and shows the sensitivity of chondrite compositions to excursions in temperature. Elements such as S and Hg have the most active response to temperature across different meteorite groups. Labile element mobilization in primitive meteorites is essential for quantifying elemental fractionation that occurred on asteroids early in Solar System history. This work is relevant to maintaining a pristine sample from asteroid (101955) Bennu from the OSIRIS-REx mission and constraining the past orbital history of Bennu. Additionally, we discuss thermal effects on surface processes of near-Earth asteroids, including the thermal history of "rock comets" such as (3200) Phaethon. This work is also critical for constraining the concentrations of contaminants in vaporized water extracted from asteroid regolith as part of future in situ resource utilization for sustained robotic and human space exploration.Comment: 12 pages of text, 3 tables, 7 figures, accepted by Icaru

Addictive links: The motivational value of adaptive link annotation

Adaptive link annotation is a popular adaptive navigation support technology. Empirical studies of adaptive annotation in the educational context have demonstrated that it can help students to acquire knowledge faster, improve learning outcomes, reduce navigational overhead, and encourage non-sequential navigation. In this paper, we present our exploration of a lesser known effect of adaptive annotation, its ability to significantly increase students' motivation to work with non-mandatory educational content. We explored this effect and confirmed its significance in the context of two different adaptive hypermedia systems. The paper presents and discusses the results of our work

A Study Of The Security Of Electronic Medical Records Utilizing Six Knowledge Categories And Subjects Demographics

Healthcare employees with their motivation to comply with security policies play an extremely important role in protecting patients’ privacy. In this research we attempt to survey the attitude of healthcare employees towards security of Electronic Medical Records. We further review what factors impact their perception of the medical data security and determine how well they understand policies, procedures, organization structures, and other aspects related to EMR protection.

A Comprehensive Study Of The Perceptions And Support Structures Of Women Engaged In IT/IS Careers

Women engaged in the Information Technology/Information Systems (IT/IS) sphere of the American collegiate and corporate experience have made significant strides in employment and opportunities for advancement culminating in the recent achievement of women reaching the CEO and presidential levels of the largest corporations in the IT sphere. Despite this significant and welcomed departure from past experiences, the progression of women matriculating in the university IT/IS major, and following through to the career phase has not materialized in numbers that equal the proliferation of male entrants. This research study relates to the factors that have the most influence on the perceptions, constraints and positive experiences leading to the choice of career development at the collegiate level. The specific areas that will be investigated and tabulated within this context are that of role models, mentoring, pre-college perceptions, and equal opportunity considerations

SO_2-rock interaction on Io 2. Interaction with pure SO_2

A Na-S mineral on the surface of Io is required to be the source of the famous atomic cloud. SO_2 is a confirmed atmospheric and surface constituent, and because of the rapid volcanic resurfacing rate, the SO_2 is buried within the crust, where at least occasionally, over many cycles of burial and eruption, it must contact silicate materials at midlevel crustal temperatures. Surface interaction experiments were performed for a wide variety of silicate compositions showing that interaction products of these with SO_2 could be observed at 1123 K on laboratory timescales, even in the absence of external redox agents. Not all experiments produced deposits that could be studied by scanning electron microscopy; some required the greater sensitivity of photoelectron spectroscopy (XPS). Characterization of the alteration products by XPS showed that both oxidized and reduced sulfur species were formed, indicating that a disproportionation mechanism producing a sulfate and a reduced S species although smaller amounts of interaction leading to Na_2SO_3 formation cannot be ruled out. The reduced sulfur species is best explained as elemental S which was independently documented for two compositions. Scanning electron microscopy studies for those compositions where reaction was extensive enough to be observed showed (1) Na_2SO_4 for a soda-lime composition, (2) a mixed Na-Ca-sulfate liquid and CaSO_4 for AbAnDi and a chondrule glass composition, and (3) Fe-sulfate for a natural obsidian. Infrared spectroscopy for the soda-lime glass composition showed peaks best explained by Na_2SO_4. We conclude that SO_2 disproportionation as well as direct formation from SO_3 under oxidizing conditions can produce Na_2SO_4 by interaction of SO_2 with silicates on Io, but Ca and Fe sulfates may form preferentially in more basaltic compositions. As highly oxidizing conditions may be unlikely for Io, the disproportionation mechanism may be more competitive on Io than it is in laboratory experiments. Very low rates of Na_2SO_4 production are required to supply the Io atomic cloud, so the interaction processes can be very inefficient