Search results for "Secondary"
showing 10 items of 1765 documents
RADIOISOTOPE MASS SPECTROMETRY
2003
Mass spectrometric methods are very sensitive and enable in many cases a multielement determination of trace and ultratrace elements combined with a good isotopic analysis ( Bacon et al. , 2001 ). Therefore, these techniques are also applied for the detection of long-lived radionuclides ( Becker and Dietze, 2000 ) mainly in environmental samples ( Adriaens et al. , 1992 ; Bailey et al. , 1993 ; Bibler et al. , 1998 ; Eroglu et al. , 1998 ; Edmonds et al. , 1998 ; Becker and Dietze, 1999 ; Wendt et al. , 1999 ), nuclear materials ( Betti, 1997 ; Chartier et al. , 1999 ), glass and ceramics ( Rohr et al. , 1994 ; Fukuda and Sayama, 1997 ), and in high-purity substances ( Beer and Heumann, 199…
High-sensitivity U–Pb rutile dating by secondary ion mass spectrometry (SIMS) with an O2+ primary beam
2012
Abstract We present a secondary ionization mass spectrometry (SIMS) technique for U–Pb geochronology of rutile at high spatial resolution and sensitivity using an O2+ primary ion beam coupled with surficial O2 gas deposition (O2 flooding). The O2+ beam is ~ 10 × more intense than conventionally applied O− or O2− beams at the same lateral resolution. Natural and synthetic rutile was determined to be conductive under O2+ bombardment, permitting higher excavation (sputter) rates than conventional SIMS using negatively charged O-beams without detrimental effects of sample charging. The main advantage of O2+ is rapid sputtering at shallow primary ion penetration depths. This minimizes the contri…
Cluster isobars for high-precision mass spectrometry
1991
Doublet mass measurements of the isobars28Si3 and12C7 are performed by use of a Penning trap mass spectrometer and the Fourier transform ion cyclotron resonance (FT-ICR). The carbon and silicon cluster ions are produced by laser ablation. Results of these preliminary measurements are presented.
The use of local electrochemical probes and surface analysis methods to study the electrochemical behaviour and pitting corrosion of stainless steels
2007
Abstract In this paper, the electrochemical microcell technique is combined with ex situ (SIMS and XPS) and in situ (SVET) techniques to study the electrochemical behaviour and pitting corrosion of inclusion-contaning stainless steels. Dissolution of metallurgical heterogeneities, depassivation and pitting mechanisms are first discussed in 1 M NaClO4, pH 3, and 1 M NaCl, pH 3, by considering the chemical composition and morphology of inclusions. The influence of the chemical composition of passive films on the electrochemical reactions and the microgalvanic coupling processes occurring at the corrosion potential is also investigated on the same specimen microstructure.
Effect of Impregnation and Activation Conditions of Al2O3/CuO Supported Monolith Catalysts in the Reduction of NO
1979
Reduction of NO in the presence of CO and Ar was examined on two series of monolithic sheets carrying an active CuO/Al 2 O 3 layer. In the impregnation procedure the ratio of Al 2 O 3 to CuO was varied in a wide range. The texture of the layer and the dispersion of CuO therein was controlled by mercury porosimetry, scanning electron microscopy and secondary ion mass spectrometry (SIMS). It could be established that the surface concentration of CuO determined by SIMS measurements is the most decisive quantity of the catalyst correlating linearly with the conversion of NO.
Citing as a sourcing practice: students’ citing self-selected online sources in their essays (Las citas como práctica del uso de las fuentes: las cit…
2020
This study examined upper secondary school students’ citations of self-selected online sources in their essays. Students (n = 140) conducted online inquiry about either effects of social media on people’s quality of life (SM) or allowance of genetic manipulation of organisms (GMO). Students, working either individually or in pairs, explored online sources with the help of a graphic organizer, after which they composed their essays. To capture the quality of citations identified in the essays, they were evaluated in terms of accuracy and richness of source features. Further, regression analysis was used to examine the effect of topic, grade level and work mode on the number and quality of ci…
The Transition to Upper Secondary Level After Basic Education for Adolescents with Autism Spectrum Disorder in Finland
2019
This chapter provides an exploration of the preparation of pupils with autism spectrum disorder (ASD) for transition to upper secondary level after Finnish basic education. It also examines the importance of supports required during the transition phase. Two examples of pupils with ASD (Kalle and Maija) are utilized to illustrate how to plan and support pupils with ASD during their initial post-school transition. Transitions are defined, after which education opportunities after basic education for pupils with ASD in Finland are examined. This is followed by a brief illustration of the Finnish comprehensive school system to provide context with a focus on support arrangements and the prepar…
Argument graph as a tool for promoting collaborative online reading
2012
This study explored how the construction of an argument graph promotes students' collaborative online reading compared to note-taking. Upper secondary school students (n = 76) worked in pairs. The pairs were asked to search for and read source material on the Web for a joint essay and either construct an argument graph or take notes during online reading. The data consist of transcription protocols of student pairs' discussions and joint essays. The study indicated that argument graphs may be useful tools when teachers want students to pay attention to the argumentative content of online sources and to consider relations between arguments. Additionally, with argument graphs, teachers can su…
Adolescents’ Self-Concordance, School Engagement, and Burnout Predict Their Educational Trajectories 1This paper is part of a series on “Youth Develo…
2009
This study investigated whether self-concordance of adolescents’ achievement-related goal predicts their school engagement and lack of burnout during upper secondary school as well as their subsequent educational trajectories. We also examined whether goal effort and progress mediate these associations. The sample consisted of 614 17-year-old upper secondary school students, who were surveyed three times: (1) in the second grade of upper secondary, (2) in the third grade of upper secondary school, and (3) one year later. The results showed that when adolescents pursued their achievement-related goal for internal reasons, they also invested effort in their goal, which was reflected in a hig…
Toward a model for students’ combinatorial thinking
2021
Abstract Combinatorics has many applications in different disciplines, however, only a few studies have explored students’ combinatorial thinking at the upper secondary and tertiary levels concurrently. The present research is a grounded theory study of eight Year 12 and five undergraduate students, who have participated in semi-structured interviews and responded to eight combinatorial tasks. Three types of combinatorial tasks were designed: combinatorial reasoning, evaluating, and problem-posing tasks. In the open coding phase of data analysis, seventy-one codes were identified which categorized into seven main categories at the axial coding phase. At the selective coding phase, five rela…