A Preliminary Study of the Separation of the Copper Sulfides from Sphalerite and the Effect of Certain Reagents on Some of the Pure Copper Minerals in Synthetic Mixtures

The problem of separating the copper sulfide minerals from sphalerite, in copper - zinc ores, has been a difficult one. This is largely due to the lack of adequate research and the small amount of data obtainable on the behavior of copper and zinc sulfide minerals in flotation circuits

SAGA: Sparse And Geometry-Aware non-negative matrix factorization through non-linear local embedding

International audienceThis paper presents a new non-negative matrix factorization technique which (1) allows the decomposition of the original data on multiple latent factors accounting for the geometrical structure of the manifold embedding the data; (2) provides an optimal representation with a controllable level of sparsity; (3) has an overall linear complexity allowing handling in tractable time large and high dimensional datasets. It operates by coding the data with respect to local neighbors with non-linear weights. This locality is obtained as a consequence of the simultaneous sparsity and convexity constraints. Our method is demonstrated over several experiments, including a feature extraction and classification task, where it achieves better performances than the state-of-the-art factorization methods, with a shorter computational time

The Dream About the Magic Silver Bullet – the Complexity of Designing for Tablet-Mediated Learning

In this paper, we report three cases of the integration of technology such as web-enabled media tablets in Scandinavian schools. Both qualitative and quantitative data have been applied. A daily challenge for teachers is to coordinate their group of students in a way that enables collaborative learning. We report the gaps and interrelations between the dreams and the practice of the teachers. They dream about an interconnected praxis -- the magic silver bullet -- and establish their visions of inter-connectivity because of their breakdown experiences of media tablets aiding complexity instead of reducing it. The teachers must learn how to navigate during the breakdowns before media tablets reduce complexity and reach a state in which the tablets take part in the classroom ecology as functional organs. The teachers have to deal with complex situations during class in situ. In order to be able to continue with the class, the teachers become jongleurs of different design elements including the handling of the didactical designs and the breakdowns caused by the integration of media tablets; the teaching practice in classrooms moves away from a common routine activity and turns into a design project

European perspectives on regional estimates of standing water bodies and the relevance of man-made ponds

International audienceThe majority of terrestrial standing water bodies (SWB) are small in size, however, their abundance and distribution is not fully known and they are under-represented in legislation. Also, the models for global inventories of SWB are so far not sufficiently designed for estimating the relative abundance of small SWB (below 0.2 ha) and provide differing estimates. In this pilot study, we suggest a bottom-up approach for estimating the number of SWB at EU-level that combines the ground-validated data on water bodies from state inventories and data from peer-generated map databases; we assess the inventories and relative importance of small terrestrial water bodies of two different countries, Estonia and France

Land Use Changes and Pheasant Declines in Eastern South Dakota

Changes in pheasant (Phasianus colchicus) nesting habitat were investigated on Windsor Township, Brookings County, South Dakota. The population was censused, nesting densities determined, cover was mapped, and an interspersion index determined in 197 7 and 1978. Comparison to a similar study conducted in 1958 and 1959 indicated a decrease in pheasant numbers of 93% for crow counts and 94% in brood counts. Nesting densities decreased by 96%. Pheasant nests were found in about the same proportions per cover type for the two time periods. Hatching success, clutch size, rates of abandonment, and nest destruction were also similar. Nesting habitat occurred on 70% of the study area in 1958, 62% in 1959, 74% in 197 7, and 66% in 1978. The mean field size was 6.7 ha in 1958, 6.9 ha in 1959, 10.2 ha in 197 7, and 8.0 ha in 1978. The interspersion index decreased by 4% from 1958-59 to 197 7-78. Although land use changes have resulted in reduction of habitat in twenty years the amount of habitat reduction does not compare to the reduction in pheasant numbers. Factors such as cover quality, which could not be measured quantitatively, may be more responsible for decreasing the pheasant population in eastern South Dakota than cover quantity

Parthenogenesis did not consistently evolve in insular populations of Ischnura hastata (Odonata, Coenagrionidae)

1. The evolutionary advantages that have driven the evolution of sex are still very much debated, and a number of benefits of parthenogenesis over sexual reproduction have been proposed. In particular, parthenogenetic individuals are thought to exhibit higher probabilities of establishment following arrival in new, isolated habitats such as islands. 2. One notable example of parthenogenesis occurring in islands is the damselfly Ischnura hastata, an American species that has colonised the Azores archipelago, where the populations consist only of females. This is the only known example of parthenogenesis within the insect order Odonata. 3. Here, two island populations of I. hastata were studied, one in the Galapagos and one in Cuba, to test whether island colonisation is consistently associated with parthenogenesis in this species. Field capture-mark-recapture studies and laboratory rearing of field-collected eggs were undertaken in both areas. 4. Sex ratios in the field were found to be heavily female-biased among mature individuals; however, fertility rates of field-collected eggs were high, and the sex ratios in the laboratory did not differ from 1:1. Data from laboratory rearing showed that shorter larval development times and shorter adult life spans in males result in protandry, which might explain the skewed sex ratios in the field. 5. These findings are consistent with sex differences in key demographic parameters which could predispose I. hastata to parthenogenesis. However, the Azores population of I. hastata remains the only documented case of asexual reproduction in this insect group