| 1. |
- Adebahr, Josefina, et al.
(författare)
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Cation coordination in ion-conducting gels based on PEO-grafted polymers
- 2000
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Ingår i: Solid State Ionics. - 0167-2738. ; 135:1-4, s. 149-154
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Tidskriftsartikel (refereegranskat)abstract
- Ionic conducting polymer gels prepared from PEG-grafted acrylates, ethylene carbonate (EC), dimethyl carbonate (DMC), and LiPF6 are studied by means of infrared and Raman spectroscopy. It is found that the presence of grafted PEO chains substantially changes the coordination of lithium cations from 'cation-solvent' to 'cation-polymer'. Spectroscopic studies show that Li+-PEO coordination is strongly favored in competition with the solvent molecules and dominates completely at ether oxygen to Li-cation ratios (O:Li) of 10:1 and 5:1. At an O:M of 4:1 a solvent-cation interaction arises, in agreement with previously reported MD calculations of a preferred coordination number of 5 in similar systems. The results suggest that the complex interactions which determine long time stability and ionic transport properties can be designed by functionalization of the polymer backbone in PMMA-based gel electrolytes.
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| 2. |
- Adebahr, J, et al.
(författare)
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Ion and solvent dynamics in gel electrolytes based on ethylene oxide grafted acrylate polymers
- 2002
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106 .- 1089-5647. ; 106:47, s. 12119-12123
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Tidskriftsartikel (refereegranskat)abstract
- Multinuclear pulsed field gradient NMR measurements and theological viscosity measurements were performed on three series of polymer gel electrolytes. The gels were based on a lithium salt electrolyte swollen into a copolymer matrix comprising an acrylate backbone and ethylene oxide side chains. In each series the side chains differed in length and number, but the acrylate-to-ethylene oxide ratio was kept constant. It was found that the self-diffusion coefficient of the cations was much lower than that of the anions, and that it decreased rapidly when the side chains got longer. In contrast, the self-diffusion coefficient of the anions was found to be independent of chain length. In the gel electrolytes, the diffusion coefficients of the solvent molecules are relatively constant despite an increased viscosity with increasing length of the side chains. However, in saltfree gels made for comparison, the diffusion coefficients of the solvent molecules decreased with, increasing length of the side chains, which is consistent with an increased viscosity.
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| 3. |
- Adebahr, Josefina, et al.
(författare)
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Li-7 NMR measurements of polymer gel electrolytes
- 2002
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Ingår i: Solid State Ionics. - 0167-2738. ; 147:3-4, s. 303-307
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Tidskriftsartikel (refereegranskat)abstract
- Ion conducting polymer gels prepared from (ethylene oxide)(n) grafted methacrylates, ethylene carbonate (EC), gamma butyrolactone (gBL), and lithium hexafluorophosphate are studied by means of nuclear magnetic resonance spectroscopy, This study shows that there are at least two possible lithium sites with different mobility. The lithium-ions with lower mobility dominate at room temperature, but this is changed as the temperature is increased. The NMR results also show that the Li-7 spin-spin relaxation time decreases with increasing length of the grafted ethylene oxide side chains, indicating a stronger interaction between the polymer and the Li-ions, and hence, a lower mobility of the Li-ions. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 4. |
- Adebahr, Josefina, 1973, et al.
(författare)
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Lithium coordination and mobility in gel electrolytes based on an acrylate polymer with ethylene oxide side chains
- 2003
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 1364-5501 .- 0959-9428. ; 13:4, s. 814-817
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Tidskriftsartikel (refereegranskat)abstract
- Multinuclear NMR has been used to investigate the structure and mobility of a series of polymer gel electrolytes. The co-polymers used as matrixes in the gels have acrylate backbones and side chains of ethylene oxide, where the length of the side chains has been varied, while the ratio of acrylate to ethylene oxide has been kept constant. The electrolyte is a mixture of lithium perchlorate and two solvents, ethylene carbonate and gamma butyrolactone. 13 C spectra of the different gel electrolytes shows that both solvents interact with the salt, and that the strength of the interaction increases with decreasing length of the polymer side chains. It also appears that the lithium ions show no selectivity between the two types of solvent. Furthermore, the lithium chemical shift moves progressively upfield with increasing length of the side chains, showing a gradual change in interaction from lithium-solvent to lithium-(ethylene oxide).
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| 5. |
- Akenine-Möller, Tomas, et al.
(författare)
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Approximate Soft Shadows on Arbitrary Surfaces using Penumbra Wedges
- 2002
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Ingår i: EGRW '02 Proceedings of the 13th Eurographics workshop on Rendering. - 1581135343 ; , s. 297-306
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Konferensbidrag (refereegranskat)abstract
- Shadow generation has been subject to serious investigation in computer graphics, and many clever algorithms have been suggested. However, previous algorithms cannot render high quality soft shadows onto arbitrary, animated objects in real time. Pursuing this goal, we present a new soft shadow algorithm that extends the standard shadow volume algorithm by replacing each shadow quadrilateral with a new primitive, called the penumbra wedge. For each silhouette edge as seen from the light source, a penumbra wedge is created that approximately models the penumbra volume that this edge gives rise to. Together the penumbra wedges can render images that often are remarkably close to more precisely rendered soft shadows. Furthermore, our new primitive is designed so that it can be rasterized efficiently. Many real-time algorithms can only use planes as shadow receivers, while ours can handle arbitrary shadow receivers. The proposed algorithm can be of great value to, e.g., 3D computer games, especially since it is highly likely that this algorithm can be implemented on programmable graphics hardware coming out within the next year, and because games often prefer perceptually convincing shadows.
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| 6. |
- Akenine-Möller, Tomas, et al.
(författare)
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Graphics for the Masses: A Hardware Rasterization Architecture for Mobile Phones
- 2003
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Ingår i: ACM Transactions on Graphics. - : Association for Computing Machinery (ACM). - 1557-7368 .- 0730-0301. ; 22:3, s. 801-808
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Konferensbidrag (refereegranskat)abstract
- The mobile phone is one of the most widespread devices with rendering capabilities. Those capabilities have been very limited because the resources on such devices are extremely scarce; small amounts of memory, little bandwidth, little chip area dedicated for special purposes, and limited power consumption. The small display resolutions present a further challenge; the angle subtended by a pixel is relatively large, and therefore reasonably high quality rendering is needed to generate high fidelity images.To increase the mobile rendering capabilities, we propose a new hardware architecture for rasterizing textured triangles. Our architecture focuses on saving memory bandwidth, since an external memory access typically is one of the most energy-consuming operations, and because mobile phones need to use as little power as possible. Therefore, our system includes three new key innovations: 1) an inexpensive multisampling scheme that gives relatively high quality at the same cost of previous inexpensive schemes, II) a texture minification system, including texture compression, which gives quality relatively close to trilinear mipmapping at the cost of 1.33 32-bit memory accesses on average, III) a scanline-based culling scheme that avoids a significant amount of z-buffer reads, and that only requires one context. Software simulations show that these three innovations together significantly reduce the memory bandwidth. and thus also the power consumption.
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| 7. |
- Akenine-Möller, Tomas, et al.
(författare)
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On the Degree of Vertices in a Shadow Volume Silhouette
- 2003
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Ingår i: Journal of Graphics Tools. - : Informa UK Limited. - 1086-7651 .- 2151-237X. ; 8:4, s. 21-24
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Tidskriftsartikel (refereegranskat)abstract
- In shadow volume rendering, the shadow volume silhouette edges are used to create primitives that model the shadow volume. A common misconception is that the vertices on such silhouettes can only be connected to two silhouette edges, i.e., have degree two. Furthermore, some believe that such a vertex can have any degree. In this short note, we present a geometric proof that shows that the degree of a silhouette vertex must be even, and not necessarily two.
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| 8. |
- Akenine-Möller, Tomas, et al.
(författare)
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Real-Time Rendering
- 2002
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Bok (övrigt vetenskapligt/konstnärligt)
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| 9. |
- Anderson, John B, et al.
(författare)
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Coded Modulation Systems
- 2003
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Ingår i: Kluwer Academic / Plenum Publishers. - 0306472791
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- This textbook studies the 3 main types of coded modulation: trellis-coded modulation (TCM), continuous-phase modulation (CPM) codes, and linear modulation codes like those that arise from filtering and intersymbol interference. In 2 final chapters, code-division multiple-access receivers are discussed. The book begins with a review of coding, modulation and information theory.
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| 10. |
- Andersson, Niklas, 1970, et al.
(författare)
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Drug-induced prevention of gastrectomy- and ovariectomy-induced osteopaenia in the young female rat.
- 2002
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Ingår i: The Journal of endocrinology. - : Bioscientifica. - 0022-0795 .- 1479-6805. ; 175:3, s. 695-703
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Tidskriftsartikel (refereegranskat)abstract
- Both ovariectomy (Ovx) and gastrectomy (Gx) induce osteopaenia in rats and humans. While the effect of Ovx has been ascribed to oestrogen deficiency, the underlying mechanism behind Gx is poorly understood. Alendronate, oestrogen and parathyroid hormone (PTH) are known to prevent the osteopaenia induced by Ovx in rats. The purpose of the present study was to determine whether alendronate, oestrogen or PTH could also prevent Gx-evoked osteopaenia. Rats were Ovx-, Gx-, or were sham-operated (Sham) and were then treated with alendronate (50 micro g/kg/day), oestrogen (10 micro g/kg/day) or PTH(1-84) (75 micro g/kg/day) for eight weeks. At sacrifice, serum PTH was unaffected by surgery (Ovx, 64+/-8 pg/ml; Gx, 75+/-13 pg/ml; Sham, 58+/-11 pg/ml). The bone mineral density (BMD) of the fifth lumbar vertebra (L5) was analysed. Ovx and Gx reduced the BMD (ash weight/Volume) of the L5 by 15+/-4% and 22+/-3% respectively. Trabecular BMD and the cortical bone mineral content (BMC) of the femur were assessed using peripheral computed tomography. Both Ovx and Gx markedly reduced trabecular BMD in the metaphyseal area of the distal femur (Ovx, -37+/-7%; Gx, -49+/-7%). The cortical BMC of the femur was only slightly reduced. Alendronate prevented trabecular bone loss after both Ovx and Gx, while oestrogen and PTH prevented trabecular bone loss after Ovx but not after Gx. In conclusion, the bisphosphonate alendronate prevented both Ovx- and Gx-induced trabecular bone loss. In contrast, PTH and oestrogen prevented Ovx-induced but not Gx-induced trabecular bone loss, suggesting that the mechanism behind the trabecular bone loss in Ovx rats differs from that in Gx rats. The results support the notion that the mechanism of action for the bone-sparing effect of these drugs differs. The ability of alendronate, and probably also other bisphosphonates, to prevent Gx-evoked osteopaenia in the rat might be of potential clinical interest when dealing with post-Gx osteopaenia in humans.
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