2,458 research outputs found
Theoretical frameworks for the learning of geometrical reasoning
No full textWith the growth in interest in geometrical ideas it is important to be clear about the nature of geometrical reasoning and how it develops. This paper provides an overview of three theoretical frameworks for the learning of geometrical reasoning: the van Hiele model of thinking in geometry, Fischbein’s theory of figural concepts, and Duval’s cognitive model of geometrical reasoning. Each of these frameworks provides theoretical resources to support research into the development of geometrical reasoning in students and related aspects of visualisation and construction. This overview concludes that much research about the deep process of the development and the learning of visualisation and reasoning is still needed
Caridina variabilis Mazancourt & Marquet & Rogers & Keith 2018, n. sp.
No full textCaridina variabilis, n. sp. (Fig. 4) Material examined. Holotype: PALAU. MNHN-IU- 2017-2082 (DNA: CA1026) 1♂ cl 3.4 mm, Tabecheding River 27/02/2011, 07°27.169N, 134°31.748E. Paratypes: PALAU. One male cl 2.4 mm (MNHN-IU- 2017-2083, DNA: CA1032) and three non-ovigerous females cl 4.1 mm (MNHN-IU- 2017-2084 DNA: CA1029) 4.8 mm (MNHN-IU- 2017-2085 DNA: CA1025) & cl. 4.9 mm (MNHN-IU- 2017-2086 DNA: CA1030), Tabecheding river 27/02/2011, 07°27.169N, 134°31.748E. 2♀ ovig cl 4.0 mm (MNHN-IU- 2017-2087 DNA: CA1149) & 4.4 mm (MNHN-IU- 2017-2088 DNA: CA1148), Ngerchokl River 27/02/2011, 07°36.527N, 134°36.958E. 1♀ ovig cl 3.9 mm (MNHN-IU- 2017-2089 DNA: CA1111), Kirelauch River 28/02/2011, 07°41.417N, 134°37.754E. 2♂ cl 3.2 mm (MNHN-IU- 2017-2090) & 3.3 mm (MNHN-IU- 2017-2091), West Coast stream Northern Tip 28/02/2011, 07°43.056N, 134°36.924E. 1♀ cl 3.8 mm (MNHN-IU- 2017-2092 DNA: CA1106) and 2♀ ovig cl 4.2 mm (MNHN-IU- 2017-2093 DNA: CA1104) & 3.8 mm (MNHN-IU- 2017-2094 DNA: CA1107), small stream East Coast 07°29.909N, 134°38.099E. 1♀ ovig cl 4.2 mm (MNHN-IU- 2017-2095 DNA: CA1020), Ngermeskang River 01/03/2011, altitude: 75m, 07°32.484N, 134°34.670E. 1♀ ovig cl 4.4 mm (MNHN-IU- 2017-2096 DNA: CA1203), Ngardmau Waterfall 02/03/2011, 07°35.482N, 134°35.573E. 1♀ cl 3.6 mm (MNHN-IU- 2017-2097 DNA: CA1204), Mesekelat River 03/03/2011, 07°26.305N, 134°34.321E. PALAU Not C. b. uncata Holthuis: USNM 105430: holotype, 1♀ ovig cl 3.5 mm Arakitaoch River; USNM 105434: paratype, 1♀ cl 4.4 mm. Not C. brachydactyla: USNM 172589: 1♂ cl 2.5 mm and 1♀ cl 3.0 mm; USNM 172590: 1♀ cl 5.5 mm. GUAM. Assan River: DCR (D. Christopher Rogers collections) 9♂ cl 2.7 mm (MNHN-IU- 2017-2098 DNA: CA1535), 3.5 mm (MNHN-IU- 2017-2099 DNA: CA1536), 2.3 mm (MNHN-IU- 2017-2100 DNA: CA1537), 2.7 mm (MNHN-IU- 2017-2101 DNA: CA1539), 2.8 mm (MNHN-IU- 2017-2102 DNA: CA1540), 2.4 mm (MNHN- IU- 2017-2103 DNA: CA1541), 2.2 mm (MNHN-IU- 2017-2104 DNA: CA1542), 2.7 mm (MNHN-IU- 2017-2102 DNA: CA1543), 2.3 mm (MNHN-IU- 2017-2105 DNA: CA1544) and 1♀ ovig cl 4.5 mm (MNHN-IU- 2017-2106 DNA: CA1538). BPBM 4227 1♀ ovig cl 4.4 mm; 13° 28' 18.24"N, 144° 42' 48.66"E; 03/02/2011; DCR: 14♂ cl 2.1–3.4 mm, 6♀ cl 2.8–3.3 mm, and 4♀ ovig cl 3.4–4.3 mm; 13° 28' 18.24"N, 144 ° 42' 48.66"E. 02/02/2011. Masso River: DCR: 9♂ cl 2.2–3.6 mm, 3♀ cl 2.7–3.2 mm, and 13♀ ovig cl 3.4–4.5 mm; 13° 27' 32.85"N, 144° 41' 54.26"E; 1 February 2011. Namo River: 2♂ cl 2.4–2.8 mm, 2♀ cl 2.6–3.0 mm, and 11♀ ovig cl 3.4–4.2 mm; 13° 23' 58.59"N, 144° 39' 58.81"E; 01/02/2011. DCR: 6♂ cl 2.4–3.1 mm; 13° 23' 57.16"N, 144° 40' 05.22"E; 02/02/ 2011. Ceti River: 1♀ cl 2.3 mm, and 7♀ ovig cl 3.1–4.1 mm; 13° 19' 34.66"N, 144° 40' 09.12"E; 31/01/2011. Toguan River: 29♂ cl 2.0– 3.4 mm, 16♀ cl 2.4–3.5 mm, and 34♀ ovig cl 3.5–4.3 mm; 13° 17' 17.94"N, 144° 39' 55.77"E; 31/01/2011. DCR: 8♂ cl 2.2–3.4 mm, 1♀ cl 2.6 mm, and 9♀ ovig cl 3.6–4.0 mm; 13° 17' 15.79"N, 144° 40' 02.51"E; 02/02/2011. Ylig River: 1♂ cl 2.4 mm, and 3♀ ovig cl 3.3–4.1 mm; 13° 23' 46.21"N, 144° 45' 54.85"E; 30/01/2011. MARIANA ISLANDS (Island not specified): Not C. brachydactyla: MNHN-IU-2015-1824: 2♀ ovig cl 4.2–5.2 mm.Published as part of Mazancourt, Valentin De, Marquet, Gerard, Rogers, D. Christopher & Keith, Philippe, 2018, Description of a new species of Caridina (Crustacea: Decapoda: Atyidae) from two Micronesian islands (Guam and Babeldaob), pp. 39-50 in Zootaxa 4377 (1) on pages 43-44, DOI: 10.11646/zootaxa.4377.1.3, http://zenodo.org/record/116323
The shaping of student knowledge: learning with dynamic geometry software
No full textThe focus of this paper is a software genre usually referred to as ‘dynamic geometry’ because of the ability of the user to dynamically manipulate geometrical figures created with the software tool. Using data from a longitudinal study of 12-13 students’ use of dynamic geometry software, the focus of the analysis is on the interpretations the students make of geometrical objects and relationships when using this form of software. The analysis suggests that the students’ mathematical reasoning is shaped by their interactions with the software in that their ability to explain geometrical facts and relationships evolves from imprecise, ‘everyday’ expressions, through reasoning that is overtly mediated by the software environment, to mathematical explanations of the geometric situation that transcend the particular tool being used. Such findings suggest that curriculum initiatives that encourage the use of dynamic geometry software are appropriate but that the incorporation of such software into classroom practices is unlikely to be straightforward
Thermochemical and kinetic aspects of the sulfurization of Cu–Sb and Cu–Bi thin films
No full textpeer reviewedCuSbS2 and Cu3BiS3 are being investigated as part of a search for new absorber materials for photovoltaic devices. Thin films of these chalcogenides were produced by conversion of stacked and co-electroplated metal precursor layers in the presence of elemental sulfur vapour. Ex-situ XRD and SEM/EDS analyses of the processed samples were employed to study the reaction sequence with the aim of achieving compact layer morphologies. A new “Time-Temperature-Reaction” (TTR) diagram and modified Pilling–Bedworth coefficients have been introduced for the description and interpretation of the reaction kinetics. For equal processing times, the minimum temperature required for CuSbS2 to appear is substantially lower than for Cu3BiS3, suggesting that interdiffusion across the interfaces between the binary sulfides is a key step in the formation of the ternary compounds. The effects of the heating rate and sulfur partial pressure on the phase evolution as well as the potential losses of Sb and Bi during the processes have been investigated experimentally and the results related to the equilibrium pressure diagrams obtained via thermochemical computation.Supergen: Photovoltaic Materials for the 21st Century EP/F029624/
FIGURE 2 in Description of a new species of Caridina (Crustacea: Decapoda: Atyidae) from two Micronesian islands (Guam and Babeldaob)
No full textFIGURE 2. Maximum likelihood phylogenetic tree (16S mtDNA) of the specimens. CAXXXX numbers are lab IDs of the specimens.Published as part of Mazancourt, Valentin De, Marquet, Gerard, Rogers, D. Christopher & Keith, Philippe, 2018, Description of a new species of Caridina (Crustacea: Decapoda: Atyidae) from two Micronesian islands (Guam and Babeldaob), pp. 39-50 in Zootaxa 4377 (1) on page 42, DOI: 10.11646/zootaxa.4377.1.3, http://zenodo.org/record/116323
States of South Carolina, Georgia, Alabama, and Florida.
No full textMap of South Carolina, Georgia, Alabama, and Florida by H.D. Rogers and A. Keith Johnston; engraved by W.andand A.K. Johnston, Edinburgh. Map denotes counties and districts, relief shown by hachures. In the upper margin of the map is printed: Atlas of United State & Map was Entered in Sta. Hall, London and according to act of Congress in the year 1857 by H.D. Rogers, in the Clerks office of the District of Court of Massachusetts. Map appears in: Atlas of the United States of North America (London: Edward Stanford, c1857) plate 15. Map scale [1:3,450,000] 54 1/2 miles to 1 .https://stars.library.ucf.edu/cfm-images/1837/thumbnail.jp
Using imagery to solve spatial problems
No full textThis report focuses on the use of imagery to solve a range of spatial problems. The research projects reviewed in this report offer some insight into the range of strategies used by solvers of spatial problems and point to relationships between spatial and verbal skills
The mediation of mathematical learning through the use of pedagogical tools: a sociocultural analysis
No full textA sociocultural analysis suggests that pedagogical artifacts employed in the teaching and learning of mathematics both enable and constrain learning. This paper summarises three classroom studies of mathematics learning that have utilised a sociocultural approach. Each of the studies indicates how insight can be gained into the ways in which students attempt to make sense of the mathematics they encounter
Electrochemical routes to PV: CuSbS2 and CuSbSe2 absorber films
No full textDue to the availability and low cost of the elements, the semiconductor systems Cu-Sb-Bi-S(e) and Cu-Zn-Sn-S(e) are being studied as sustainable alternatives to the expensive CuIn(Ga)S(e)2 for thin film photovoltaic applications.
The samples have been produced by a range of synthetic techniques such as one-step or multi-step electrodepositions from aqueous and non aqueous solutions and other electroplating/evaporation routes.
The new materials have been characterized through structural, electrical and photoelectrochemical techniques in order to establish their suitability as absorber layer materials for solar energy conversion. Photoactive compounds have been synthesised, with band-gap energy matching the Shockley-Queisser requirements for the efficient harvesting of solar spectrum. Further studies are being carried out in order to improve the photon to current efficiency of these materials
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