Self-assembled GaIn(N)As quantum dots: Enhanced luminescence at 1.3 µm

Self-assembled GaIn(N)As quantum dots are fabricated on GaAs by atmospheric pressuremetalorganic vapor-phase epitaxy using dimethylhydrazine (DMHy) precursor as a nitrogen source. The incorporation of nitrogen into the islands is observed to be negligible. However, the areal density of the islands is increased by up to one order of magnitude compared to that of the respective GaInAs islands. The GaIn(N)As island size can also be controlled by varying the DMHy flow. An enhancement of the room-temperature luminescence at 1.3 μm is observed in the GaIn(N)As samples grown with DMHy.Peer reviewe

Observation of defect complexes containing Ga vacancies in GaAsN

Positron annihilation spectroscopy was used to study GaAsN/GaAs epilayers. GaAsN layers were found to contain Ga vacancies in defect complexes. The density of the vacancy complexes increases rapidly to the order of 1018 cm−3 with increasing N composition and decreases after annealing at 700 °C. The anticorrelation of the vacancy concentration and the integrated photoluminescence intensity suggests that the Ga vacancy complexes act as nonradiative recombination centers.Peer reviewe

Structural properties of GaAsN/GaAs quantum wells studied at the atomic scale by cross-sectional scanning tunnelling microscopy

The nitrogen distribution in GaAsNGaAs quantum wells _QWs_ grown by molecular beam epitaxy is studied on the atomic scale by cross-sectional scanning tunneling microscopy. No nitrogen clustering is observed in the range of N contents studied _between 1.0% and 2.5%, as measured by counting the individual N atoms inside the QW_. Nevertheless, the upper interface roughness increases with the amount of N. A residual N concentration in the GaAs barriers is found, which strongly increases with the amount of N in the QW

Tensile-strained GaAsN quantum dots on InP

Self-assembled quantum dots are typically fabricated from compressive-strained material systems, e.g., InAs on GaAs. In this letter, self-assembled quantum dots from tensile-strained GaAsN on InP are demonstrated. GaAsN on InP has type-I band alignment. Stranski-Krastanov growth mode is not observed, but in situannealing of the uncapped samples results in the formation of islands. Photoluminescence spectra from the buried GaAsN show separate peaks due to a wetting layer and islands around the energies of 1.3 and 1.1eV, respectively.Peer reviewe

Community of inquiry and inquiry-based learning

Peer reviewe

Global mapping of maximum emission heights and resulting vertical profiles of wildfire emissions

The problem of characteristic vertical profile of smoke released from wildland fires is considered. A methodology for bottom-up evaluation of this profile is suggested and a corresponding global dataset is calculated. The profile estimation is based on: (i) a semi-empirical formula for plume-top height recently suggested by the authors, (ii) satellite observations of active wildland fires, and (iii) meteorological conditions evaluated for each fire using output of the numerical weather prediction model. Injection profiles of the plumes from all fires recorded globally from March 2000 till November 2012 are estimated with a time step of 1 h. The resulting 4-dimensional dataset is split into daytime and nighttime subsets. The subsets are projected onto a global grid with a resolution of 1° × 1° × 500 m, aggregated to a monthly level, and normalised by total emissions in each vertical column. Evaluation of the obtained dataset was performed in several ways. Firstly, the quality of the semi-empirical formula for plume-top computations was evaluated using updated MISR fire Plume Height Project data. Secondly, the upper percentiles of the profiles are compared with an independent dataset of space lidar CALIOP. Thirdly, the results are compared with the distribution suggested for AEROCOM modelling community. Finally, the inter-annual variations of the calculated profiles are estimated

From multiple perspectives to shared understanding

The aim of this study was to explore how learners operating in a small group reach shared understanding as they work out joint research questions and build a theoretical framework and to identify the resources and tools they used in the process. The learners’ own interpretations of their group activities and learning were also taken into account. The data, consisting of group discussions and the documents produced by the group, were subjected to a qualitative content analysis. The group members employed a variety of resources and tools to exchange their individual perspectives and achieve shared understanding. Summaries of relevant literature laid a foundation for the group’s theoretical discussions. Reflective comparisons between their book knowledge and their personal experiences of online interaction and collaboration were frequent, suggesting that such juxtapositions may have enhanced their learning by intertwining the content to be mastered and the activities entailed by this particular content

Grounding IPBES experts’ views on the multiple values of nature in epistemology, knowledge and collaborative science

This study identifies and analyses the underlying assumptions of experts involved in the first author meeting (FAM) of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)’s Values Assessment, and how they shape understandings of the multiple values of nature. We draw from survey data collected from 94 experts attending the FAM. Respondents self-report the tendencies and aims they bring to the assessment (i.e. motivation), the type and amount of evidence they require for knowledge to be valid (i.e. confirmation) and their epistemic worldviews (i.e. objectivity). Four clusters emerged that correspond to Pragmatist, Post-Positivist, Constructivist and Transformative epistemic worldviews. This result clarifies how different knowledge claims are represented in science-policy processes. Despite the proportionately higher number of social scientists in the Values Assessment, compared with previous IPBES assessments, we still found that fewer experts have Constructivist or Transformative worldviews than Pragmatist or Post-Positivist outlooks, an imbalance that may influence the types of values and valuation perspectives emphasised in the assessment. We also detected a tension regarding what constitutes valid knowledge between Post-Positivists, who emphasised high levels of agreement, and Pragmatists and Constructivists, who did not necessarily consider agreement crucial. Conversely, Post-Positivists did not align with relational values and were more diverse in their views regarding definitions of multiple values of nature compared to other clusters. Pragmatists emphasized relational values, while Constructivists tended to consider all value types (including relational values) as important. We discuss the implications of our findings for future design and delivery of IPBES processes and interdisciplinary research.This study identifies and analyses the underlying assumptions of experts involved in the first author meeting (FAM) of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES)'s Values Assessment, and how they shape understandings of the multiple values of nature. We draw from survey data collected from 94 experts attending the FAM. Respondents self-report the tendencies and aims they bring to the assessment (i.e. motivation), the type and amount of evidence they require for knowledge to be valid (i.e. confirmation) and their epistemic worldviews (i.e. objectivity). Four clusters emerged that correspond to Pragmatist, Post-Positivist, Constructivist and Transformative epistemic worldviews. This result clarifies how different knowledge claims are represented in science-policy processes. Despite the proportionately higher number of social scientists in the Values Assessment, compared with previous IPBES assessments, we still found that fewer experts have Constructivist or Transformative worldviews than Pragmatist or Post-Positivist outlooks, an imbalance that may influence the types of values and valuation perspectives emphasised in the assessment. We also detected a tension regarding what constitutes valid knowledge between Post-Positivists, who emphasised high levels of agreement, and Pragmatists and Constructivists, who did not necessarily consider agreement crucial. Conversely, Post-Positivists did not align with relational values and were more diverse in their views regarding definitions of multiple values of nature compared to other clusters. Pragmatists emphasized relational values, while Constructivists tended to consider all value types (including relational values) as important. We discuss the implications of our findings for future design and delivery of IPBES processes and interdisciplinary research.Peer reviewe

Implementing virtual collaborative inquiry practises in a middle-school context

The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.The aim of the present study was to investigate the challenges that relate to the implementation of virtual inquiry practises in middle school. The case was a school course in which a group of Finnish students (N = 14) and teachers (N = 7) completed group inquiries through virtual collaboration, using a web-based learning environment. The task was to accomplish a cross-disciplinary inquiry into cultural issues. The students worked mainly at home and took much responsibility for their course achievements. The investigators analysed the pedagogical design of the course and the content of the participants' interaction patterns in the web-based environment, using qualitative content analysis and social network analysis. The findings suggest that the students succeeded in producing distinctive cultural products, and both the students and the teachers adopted novel roles during the inquiry. The web-based learning environment was used more as a coordination tool for organizing the collaborative work than as a forum for epistemic inquiry. The tension between the school curriculum and the inquiry practises was manifest in the participants' discussions of the assessment criteria of the course.Peer reviewe