| 1. |
- Kundu, T.K., et al.
(författare)
-
Atomistic simulation of the surface structure of wollastonite and adsorption phenomena relevant to flotation
- 2003
-
Ingår i: International Journal of Mineral Processing. - 0301-7516 .- 1879-3525. ; 72:1, s. 111-127
-
Tidskriftsartikel (refereegranskat)abstract
- Atomistic simulation techniques have been used to calculate the surface structure and stability of wollastonite crystal and its adsorption behaviour in the presence of molecular and dissociated water, and two widely used collector head group molecules of methanoic acid and methylamine. Seven predominant surfaces have been modelled and their calculated surface energies correspond well with their preferred morphological domination. Surfaces are identified having fourfold and threefold coordination of surface silicon. Threefold surface silicon are stabilized by addition of hydroxyl ion on them and proton on surface oxygen. Stable surfaces thus obtained are subjected to surface Ca2+ replacement by 2H+ by transforming 2O2− to 2OH−. Surface energy and reaction energy values indicate wollastonite surface stabilized to a great extent by adsorbing water in dissociated form. The Ca2+ replacement from the first few layers of the surface is energetically more favourable in acidic condition. Three Miller indexed surfaces terminating with fully coordinated silicon were reconstructed to make the surface free of lone oxygen, and these surface cuts were chosen to carry out simulation work for adsorption of molecules. A comparison of surface energies revealed that all the surfaces become stabilized in the presence of added molecules but the presence of methylamine decreases surface energy to lowest values. Adsorption of dissociated water is preferred by {100} and {102} surfaces, while {001} surface adsorbs methylamine strongly as the results show highly negative adsorption energies. In terms of pure molecule adsorption, the preferred adsorption sequence for all the surfaces is methylamine>methanoic acid>water. For {100} and {102} predominant surfaces, the difference in adsorption energy values is not much and we conclude that the collectors having long-chain hydrophobic alkyl chain, the two head group molecules considered, cannot render enough hydrophobicity due to inadequate adsorption on wollastonite. Thus the presence of activators/modifiers in actual wollastonite flotation practice is substantiated.
|
|
| 2. |
- Mc Kee, K J, et al.
(författare)
-
The COPE index - A first stage assessment of negative impact, positive value and quality of support of caregiving in informal carers of older people
- 2003
-
Ingår i: Aging & Mental Health. - : Informa UK Limited. - 1360-7863 .- 1364-6915. ; 7:1, s. 39-52
-
Tidskriftsartikel (refereegranskat)abstract
- Data was collected in five countries from informal carers of older people (n=577) via a common protocol. Carers completed: (1) a 17-item version of the Carers of Older People in Europe (COPE) Index, an assessment of carers' perceptions of their role, (2) a questionnaire on demographic and caregiving circumstances, and (3) three instruments included for the criterion validation of the COPE Index (the General Health Questionnaire, the Hospital Anxiety and Depression Scale, and the World Health Organization Quality of Life-BREF). Principal Component Analysis of the COPE Index was followed by internal consistency analysis of emergent components. Scales derived by summing items loading on the components were analyzed for their association with the criterion measures. Two components, negative impact and positive value, emerged consistently across countries. A third component, quality of support was less consistent across countries. Scales derived from the negative impact and positive value components were internally consistent and significantly associated with the criterion validity measures. These two scales and four items drawn from the quality of support component were retained in the final COPE Index. While further testing is required, the COPE Index has current utility in increasing understanding of the role perceptions of carers of older people.
|
|
| 3. |
- Scherer, SW, et al.
(författare)
-
Human chromosome 7: DNA sequence and biology
- 2003
-
Ingår i: Science (New York, N.Y.). - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 300:5620, s. 767-772
-
Tidskriftsartikel (refereegranskat)abstract
- DNA sequence and annotation of the entire human chromosome 7, encompassing nearly 158 million nucleotides of DNA and 1917 gene structures, are presented. To generate a higher order description, additional structural features such as imprinted genes, fragile sites, and segmental duplications were integrated at the level of the DNA sequence with medical genetic data, including 440 chromosome rearrangement breakpoints associated with disease. This approach enabled the discovery of candidate genes for developmental diseases including autism.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
|
|
| 10. |
|
|
