Simultaneous dual-element analyses of refractory metals in naturally occurring matrices using resonance ionization of sputtered atoms

The combination of secondary neutral mass spectrometry (SNMS) and resonance ionization spectroscopy (RIS) has been shown to be a powerful tool for the detection of low levels of elemental impurities in solids. Drawbacks of the technique have been the laser-repetition-rate-limited, low duty cycle of the analysis and the fact that RIS schemes are limited to determinations of a single element. These problems have been addressed as part of an ongoing program to explore the usefulness of RIS/SNMS instruments for the analysis of naturally occurring samples. Efficient two-color, two-photon (1+1) resonance ionization schemes were identified for Mo and for four platinum-group elements (Ru, Os, Ir, and Re). Careful selection of the ionization schemes allowed Mo or Ru to be measured simultaneously with Re, Os, or Ir, using two tunable dye lasers and an XeCl excimer laser. Resonance frequencies could be switched easily under computer control, so that all five elements can be rapidly analyzed. In situ measurements of these elements in metal grains from five meteorites were conducted. From the analyses, estimates of the precision and the detection limit of the instrument were made. The trade-off between lower detection limits and rapid multielement RIS analyses is discussed

Cell cycle-dependent phosphorylation of Theileria annulata schizont surface proteins

The invasion of Theileria sporozoites into bovine leukocytes is rapidly followed by the destruction of the surrounding host cell membrane, allowing the parasite to establish its niche within the host cell cytoplasm. Theileria infection induces host cell transformation, characterised by increased host cell proliferation and invasiveness, and the activation of anti-apoptotic genes. This process is strictly dependent on the presence of a viable parasite. Several host cell kinases, including PI3-K, JNK, CK2 and Src-family kinases, are constitutively activated in Theileria-infected cells and contribute to the transformed phenotype. Although a number of host cell molecules, including IkB kinase and polo-like kinase 1 (Plk1), are recruited to the schizont surface, very little is known about the schizont molecules involved in host-parasite interactions. In this study we used immunofluorescence to detect phosphorylated threonine (p-Thr), serine (p-Ser) and threonine-proline (p-Thr-Pro) epitopes on the schizont during host cell cycle progression, revealing extensive schizont phosphorylation during host cell interphase. Furthermore, we established a quick protocol to isolate schizonts from infected macrophages following synchronisation in S-phase or mitosis, and used mass spectrometry to detect phosphorylated schizont proteins. In total, 65 phosphorylated Theileria proteins were detected, 15 of which are potentially secreted or expressed on the surface of the schizont and thus may be targets for host cell kinases. In particular, we describe the cell cycle-dependent phosphorylation of two T. annulata surface proteins, TaSP and p104, both of which are highly phosphorylated during host cell S-phase. TaSP and p104 are involved in mediating interactions between the parasite and the host cell cytoskeleton, which is crucial for the persistence of the parasite within the dividing host cell and the maintenance of the transformed state

But are They Good Teachers? Examining Who Takes up Teacher Leadership and How Their Instruction Differs from Their Peers

Teacher leaders function in many roles in supporting school success including instructional leadership and supporting colleagues. This study draws upon the Status of the Social Studies Survey (Fitchett & Vanfossen, 2013) to examine the responses of 6,702 US-based middle and high school social studies teachers to understand the antecedents of teacher leadership and the instructional practices of these individuals compared to their peers. Survey responses indicate that the vast majority of social studies teachers report participating in some aspect of teacher leadership. Teacher leaders tend to be less experienced and have less educational attainment while employing more research-based instructional techniques

The solar oxygen-isotopic composition: Predictions and implications for solar nebula processes

The outer layers of the Sun are thought to preserve the average isotopic and chemical composition of the solar system. The solar O-isotopic composition is essentially unmeasured, though models based on variations in meteoritic materials yield several predictions. These predictions are reviewed and possible variations on these predictions are explored. In particular, the two-component mixing model of Clayton and Mayeda (1984) (slightly revised here) predicts solar compositions to lie along an extension of the calcium-aluminum-rich inclusion (CAI) ^(16)O line between (δ^(18)O, δ^(17)O) = (16.4, 11.4)%0 and (12.3, 7.5)%0. Consideration of data from ordinary chondrites suggests that the range of predicted solar composition should extend to slightly lower δ^(18)O values. The predicted solar composition is critically sensitive to the solid/gas ratio in the meteorite-forming region, which is often considered to be significantly enriched over solar composition. A factor of two solid/gas enrichment raises the predicted solar (δ^(18)O, δ^(17)O) values along an extension of the CAI ^(16)O line to (33, 28)%0. The model is also sensitive to the nebular O gas phase. If conversion of most of the gaseous O from CO to H_2O occurred at relatively low temperatures and was incomplete at the time of CM aqueous alteration, the predicted nebular gas composition (and hence the solar composition) would be isotopically heavier along a slope 1/2 line. The likelihood of having a single solid nebular O component is discussed. A distribution of initial solid compositions along the CAI ^(16)O line (rather than simply as an end-member) would not significantly change the predictions above in at least one scenario. Even considering these variations within the mixing model, the predicted range of solar compositions is distinct from that expected if the meteoritic variations are due to non-mass-dependent fractionation. Thus, a measurement of the solar O composition to a precision of several permil would clearly distinguish between these theories and should clarify a number of other important issues regarding solar system formation

Variations in solar wind fractionation as seen by ACE/SWICS over a solar cycle and the implications for Genesis Mission results

We use ACE/SWICS elemental composition data to compare the variations in solar wind fractionation as measured by SWICS during the last solar maximum (1999-2001), the solar minimum (2006-2009) and the period in which the Genesis spacecraft was collecting solar wind (late 2001 - early 2004). We differentiate our analysis in terms of solar wind regimes (i.e. originating from interstream or coronal hole flows, or coronal mass ejecta). Abundances are normalized to the low-FIP ion magnesium to uncover correlations that are not apparent when normalizing to high-FIP ions. We find that relative to magnesium, the other low-FIP elements are measurably fractionated, but the degree of fractionation does not vary significantly over the solar cycle. For the high-FIP ions, variation in fractionation over the solar cycle is significant: greatest for Ne/Mg and C/Mg, less so for O/Mg, and the least for He/Mg. When abundance ratios are examined as a function of solar wind speed, we find a strong correlation, with the remarkable observation that the degree of fractionation follows a mass-dependent trend. We discuss the implications for correcting the Genesis sample return results to photospheric abundances.Comment: Accepted for publication in Ap

Assessing Teacher Pedagogical Knowledge: The Video Assessment of Teacher Knowledge (VATK)

This study examines the creation and implementation of a video-based assessment of teacher knowledge of effective teaching called the Video Assessment of Teacher Knowledge (VATK). The VATK was developed with the intention of creating an easily administered, standardised assessment that can potentially provide information on teacher candidate knowledge of teaching at important points during their training programmes and into the teaching field. The theoretical framework upon which the VATK was developed and the process for item creation are described. Classical test theory and item response theory analysis were conducted to determine the measure’s potential for use in future studies. Analyses indicate that after some questions are removed, the measure is sensitive to differences in teachers’ pedagogical knowledge

Принципы построения информационной системы для планирования, согласования и мониторинга геолого-технических мероприятий

Описана проблематика и информационные подходы, применяемые авторами при решении задачи ведения единой базы данных геолого-технических мероприятий, организации совместного взаимодействия проектных подразделений и недропользователя при планировании, согласовании и мониторинге геолого-технических мероприятий

A Mixed Methods Investigation of Administrators’ and Teachers’ Perceptions of Teacher Leadership

Teacher leadership has received attention for empirical and practical reasons. However, despite the evolution of the concept over the last several decades, there is still dissonance regarding the concept of teacher leadership. This study was grounded in the theory of professional identity to understand how administrators and teachers conceptualize teacher leadership. We studied the perceptions of administrators and teachers about teacher leadership using a survey and interviews. While there was some overlap in how administrators and teachers perceived teacher leadership, administrators viewed teacher leadership as occurring outside of the classroom while teachers located it inside of the classroom. Teachers also valued formal and informal mentoring. We provide implications for research and practice based on these findings

Characterisation of Float Rocks at Ireson Hill, Gale Crater

Float rocks discovered by surface missions on Mars have given unique insights into the sedimentary, diagenetic and igneous processes that have operated throughout the planets history. In addition, Gale sedimentary rocks, both float and in situ, record a combination of source compositions and diagenetic overprints. We examine a group of float rocks that were identified by the Mars Science Laboratory missions Curiosity rover at the Ireson Hill site, circa. sol 1600 using ChemCam LIBS, APXS and images from the MastCam, Mars Hand Lens Imager (MAHLI) and ChemCam Remote Micro-Imager (RMI) cameras. Geochemical data provided by the APXS and ChemCam instruments allow us to compare the compositions of these rocks to known rock types from Gale crater, as well as elsewhere on Mars. Ireson Hill is a 15 m long butte in the Murray formation with a dark cap-ping unit with chemical and stratigraphic consistency with the Stimson formation. A total of 6 float rocks have been studied on the butte

A Comparison of Solar Wind and Estimated Solar System Xenon Abundances: A Test for Solid/ Gas Fractionation in the Solar Nebula

Significant fractionation of dust/gas from the original interstellar cloud during the formation of the solar system is a distinct possibility. Identification of such an effect would provide important clues to nebular processes. Fractionation of volatiles is not constrained by CI abundances and only for the most abundant ones by photospheric observations. The solar Xe elemental abundance is determined here via solar wind measurements from lunar ilmenites and normalized to Si by spacecraft data. The results are compared with estimated abundances assuming no fractionation, which are relatively well constrained for Xe by s-process calculations, odd-mass abundance interpolations, and odd-even abundance systematics. When corrected for solar wind/photospheric fractionation, the ^(130)Xe abundance given by surface layer oxidation of ilmenite from soil 71501, exposed within the last - 200 m.y., is 0.24 ± 0.09 normalized to Si = 10^6. This is indistinguishable from the estimates made assuming no solid/gas fractionation. A similar result was obtained for Kr by Wiens et al (1991). Results from breccia 79035 ilmenite, exposed at least ~1 Gy ago, indicate that the solar wind Xe flux may have been significantly higher relative to other noble gases, perhaps due to more efficient Xe ionization. If this is true, fluxes of C and S, which have similar first ionization potentials to Xe, should also be higher in the ancient solar wind from the same time period, though such variations have not been observed