69 research outputs found
Solution composition and particle size effects on the dissolution and solubility of a ThO2 microstructural analogue for UO2 matrix of nuclear fuel
The objective of this study was to investigate the dissolution rate of ThO2 which was synthesised to approximate, as closely as possible, the microstructure of UO2 in a nuclear fuel matrix. The optimal sintering temperature for ThO2 pellets was found to be 1750ââ, which produced pellets with a microstructure similar to UO2 nuclear fuel pellets, with randomly oriented grains ranging in size from 10 to 30âÎŒm. Dissolution was conducted using ThO2 particles of different size fractions (80 to 160âÎŒm and 2 to 4âmm) in the presence and absence of carbonate, in solutions with pH from 2 to 8 and at 80ââ. Dissolution rates were calculated from Th released from the solid phase to solution. Particles of ThO2 were also leached with 1âM HNO3 at 80ââ in order to investigate the morphological changes at the particle surfaces. The concentration of Th was found to be â„â10â9âmol/L at pHââ€â4, lower than the theoretical solubility of crystalline ThO2. At higher pH values, from 4 to 8, the measured concentrations (10â10 to 10â12âmol/L) were between the theoretical solubility of ThO2 and Th(OH)4. Grain boundaries were shown to exert an influence on the dissolution of ThO2 particles. Using high resolution aqueous solution analysis, these data presented here extend the current understanding of Th solubility in solutio
Knowledge creation and management in the five LHC experiments at CERN: implications for technology innovation and transfer
The present study analyses knowledge creation, acquisition and transfer in the five LHC physics experiments at CERN: ALICE, ATLAS, CMS, LHCb, and TOTEM. A questionnaire was provided during collaboration meetings and a total of 291 replies were obtained and analysed. The results of this research study provide evidence that the social process of participation in meetings, acquisition of skills in different areas, and the development of interests by interaction with colleagues are key elements of the learning process. Furthermore, the results indicate that knowledge acquisition in a multicultural environment plays a mediating role in the interaction between social capital constructs (social interaction, relationship quality, and network ties) and competitive advantage outcomes (invention development and technological distinctiveness). Social interaction, relationship quality, and network ties are connected to greater knowledge acquisition, and also contribute to innovation and transfer of the knowledge to industry. The fertile environment of the five LHC experiments building and managing multiple processes, involves a dynamic, interactive,and simultaneous exchange of knowledge both inside and outside their organization
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The Differences and Similarities between Curiosity and Interest: Meta-analysis and Network Analyses
Three studies on the relationship between curiosity and interest are reported. The first study was a meta-analysis that examined the Pearson correlations between scales assessing curiosity and interest. Based on 24 studies (31 effect sizes), we found that the curiosity scales correlated with the interest scales at a moderate level (r = 0.53), but they had extremely high heterogeneity. The second and third studies applied network analyses (i.e., co occurrence analysis and correlation-based analysis) to data that was collected using experience sampling method. Across the studies, we found that while the feelings of curiosity reflected feelings of inquisitiveness, the feelings of interest were aligned with positive affect such as enjoyment and happiness. Importantly, an asymmetrical pattern also was found in curiosity-interest co-occurrences: when feelings of curiosity occurred, the co occurrence of feelings of interest was highly likely, but not so vice versa. Overall, our findings suggest that feelings of curiosity are special cases of feelings of interest that pertain to knowledge acquisition. Theoretical and practical implications of these findings are discussed.Peer reviewe
Teacher's reflection of inquiry teaching in finland before and during an in-service program: Examination by a progress model of collaborative reflection
In inquiry-based science education, there have been gradual shifts in research interests: the nature of scientific method, the debates on the effects of inquiry learning, and, recently, inquiry teaching. However, many in-service programs for inquiry teaching have reported inconsistent results due to the static view of classroom inquiries and due to the partial perspective between individual and collaborative reflections. Thus, by means of a theoretical progress model of collaborative reflection, this qualitative research aims to investigate reflections of four participant teachers before and during a half-year in-service teacher program. The model captures the following four interactions for each individual teacher and among the teacher cohort: belief to practice, practice to belief, stimulation, and reinforcement. The audio-video data and their quantification allowed identification of the teachers' consistent prior beliefs and practices as a multiplicity of inquiry teaching and their interwoven progress during the program. The findings are further discussed in terms of the implicit development and the richer repertoire. © 2012 National Science Council, Taiwan
PTFE Bypass or Thrupass for Superficial Femoral Artery Occlusion? A Randomised Controlled Trial
AbstractEarly results of a thrupass endograft in the treatment of femoral lesions are promising. Less morbidity and better cost-effectiveness are suggested to be achieved in the treatment of chronic lower limb ischaemia with endovascular treatment compared to surgical treatment.Patients and methodsThis randomised multicentre trial aimed to enroll a group of 60+60 patients for the treatment of 5â25-cm occlusions of superficial femoral artery (SFA) to be followed up for 3 years. Patients were treated either with endoluminal PTFE thrupass (WL Gore & Ass) or with surgical polytetrafluoroethylene (PTFE) bypass to proximal popliteal artery. Primary patency at 3 years was scheduled to be the primary end-point and secondary patency, functional success, costs and quality of life the secondary end-points.ResultsA sample of 100 consecutive SFA occlusions in one of the centres revealed that only 4% of the lesions were amenable for the study. The trial was prematurely terminated due to the results of an interim analysis at the time when 44 patients were recruited: the 1-year primary patency (excluding technical failures) was 48% for thrupass and 95% for bypass (p=0.02). The patency difference in favour of surgical bypass over endovascular thrupass was also sustained after completion of 1-year follow-up, the primary patencies being 46% and 84% at 1 year with grossly equilinear life-table curves thereafter (p=0.18), respectively. The corresponding secondary patencies were 63% and 100% (p=0.05) when excluding technical failures and 58% and 100% (p=0.02) according to intention-to-treat analysis. Secondary outcomes were thus not analysed.ConclusionTreatment of SFA occlusions (TASC IIB and C or Imelda Ia and II) should be done by PTFE bypass rather than by PTFE thrupass, as thrupass is connected with worse early outcome. These results represent only a small category of femoral disease
Teachers as Educational Innovators in Inquiry-Based Science Teaching and Learning
This chapter describes inquiry-based science teaching and learning (IBST/L) pilots designed by teachers during a professional development programme. There is research-based evidence that IBSL/T may promote studentsâ learning and their motivation to learn science, and therefore it is beneficial to familiarise the teachers with this approach. Building on teachersâ existing expertise in designing their teaching, the programme introduced theoretical aspects of the IBST/L approach and its research-based benefits for studentsâ motivation, interest and science learning. The course aimed to support teachers as educational innovators in the process of designing and testing IBST/L pilots, during which they collaboratively reflected on and revised their existing practices. The data of this piece of research consists of the teachersâ poster presentations of their IBST/L pilots and a video recording of the reflection session. The content analysis revealed that the pilotsâ structure seemed traditional but encompassed some IBST/L features. It is concluded that teacher educators need to understand teachersâ views of IBST/L in order to more effectively support planning and reflection.This chapter describes inquiry-based science teaching and learning (IBST/L) pilots designed by teachers during a professional development programme. There is research-based evidence that IBSL/T may promote studentsâ learning and their motivation to learn science, and therefore it is beneficial to familiarise the teachers with this approach. Building on teachersâ existing expertise in designing their teaching, the programme introduced theoretical aspects of the IBST/L approach and its research-based benefits for studentsâ motivation, interest and science learning. The course aimed to support teachers as educational innovators in the process of designing and testing IBST/L pilots, during which they collaboratively reflected on and revised their existing practices. The data of this piece of research consists of the teachersâ poster presentations of their IBST/L pilots and a video recording of the reflection session. The content analysis revealed that the pilotsâ structure seemed traditional but encompassed some IBST/L features. It is concluded that teacher educators need to understand teachersâ views of IBST/L in order to more effectively support planning and reflection.Peer reviewe
Simultaneous Planck, Swift, and Fermi observations of X-ray and gamma-ray selected blazars
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105
blazars belonging to three samples with flux limits in the soft X-ray, hard
X-ray, and gamma-ray bands. Our unique data set has allowed us to demonstrate
that the selection method strongly influences the results, producing biases
that cannot be ignored. Almost all the BL Lac objects have been detected by
Fermi-LAT, whereas ~40% of the flat-spectrum radio quasars (FSRQs) in the
radio, soft X-ray, and hard X-ray selected samples are still below the
gamma-ray detection limit even after integrating 27 months of Fermi-LAT data.
The radio to sub-mm spectral slope of blazars is quite flat up to ~70GHz, above
which it steepens to ~-0.65. BL Lacs have significantly flatter spectra
than FSRQs at higher frequencies. The distribution of the rest-frame
synchrotron peak frequency (\nupS) in the SED of FSRQs is the same in all the
blazar samples with =10^13.1 Hz, while the mean inverse-Compton peak
frequency, , ranges from 10^21 to 10^22 Hz. The distributions of \nupS
and of \nupIC of BL Lacs are much broader and are shifted to higher energies
than those of FSRQs and strongly depend on the selection method. The Compton
dominance of blazars ranges from ~0.2 to ~100, with only FSRQs reaching values
>3. Its distribution is broad and depends strongly on the selection method,
with gamma-ray selected blazars peaking at ~7 or more, and radio-selected
blazars at values ~1, thus implying that the assumption that the blazar power
is dominated by high-energy emission is a selection effect. Simple SSC models
cannot explain the SEDs of most of the gamma-ray detected blazars in all
samples. The SED of the blazars that were not detected by Fermi-LAT may instead
be consistent with SSC emission. Our data challenge the correlation between
bolometric luminosity and \nupS predicted by the blazar sequence.Comment: Version accepted by A&A. Joint Planck, Swift, and Fermi
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International collaborative follow - up investigation of graduating high school studentsâ understandings of the nature of scientific inquiry: is progress Being made?
Understandings of the nature of scientific inquiry (NOSI), as opposed to engaging students in inquiry learning experiences, are included in science education reform documents around the world. However, little is known about what students have learned about NOSI during their pre-college school years. The purpose of this large-scale follow-up international project (i.e. 32 countries and regions, spanning six continents and including 3917 students for the high school sample) was to collect data on what exiting high school students have learned about NOSI. Additionally, the study investigated changes in 12th grade studentsâ NOSI understandings compared to seventh grade (i.e. 20 countries and regions) studentsâ understandings from a prior investigation [Lederman et al. (2019). An international collaborative investigation of beginning seventh grade studentsâ understandings of scientific inquiry: Establishing a baseline. Journal of Research in Science Teaching, 56(4), 486â515. https://doi.org/10.1002/tea.21512]. This study documents and discusses graduating high school studentsâ understandings and compares their understandings to seventh grade studentsâ understandings of the same aspects of scientific inquiry for each country. It is important to note that collecting data from each of the 130+ countries globally was not feasible. Similarly, it was not possible to collect data from every region of each country. A concerted effort was made, however, to provide a relatively representative picture of each country and the world
Planck early results. XV. Spectral energy distributions and radio continuum spectra of northern extragalactic radio sources
Spectral energy distributions (SEDs) and radio continuum spectra are presented for a northern sample of 104 extragalactic radio sources, based
on the Planck Early Release Compact Source Catalogue (ERCSC) and simultaneous multifrequency data. The nine Planck frequencies, from 30
to 857 GHz, are complemented by a set of simultaneous observations ranging from radio to gamma-rays. This is the first extensive frequency
coverage in the radio and millimetre domains for an essentially complete sample of extragalactic radio sources, and it shows how the individual
shocks, each in their own phase of development, shape the radio spectra as they move in the relativistic jet. The SEDs presented in this paper
were fitted with second and third degree polynomials to estimate the frequencies of the synchrotron and inverse Compton (IC) peaks, and the
spectral indices of low and high frequency radio data, including the Planck ERCSC data, were calculated. SED modelling methods are discussed,
with an emphasis on proper, physical modelling of the synchrotron bump using multiple components. Planck ERCSC data also suggest that the
original accelerated electron energy spectrum could be much harder than commonly thought, with power-law index around 1.5 instead of the
canonical 2.5. The implications of this are discussed for the acceleration mechanisms effective in blazar shocks. Furthermore in many cases the
Planck data indicate that gamma-ray emission must originate in the same shocks that produce the radio emission
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