| 1. |
|
|
| 2. |
- Guo, J.-H., et al.
(författare)
-
How the phenyle rings (benzene) act as building blocks in pi conjugated polymers
- 1998
-
Ingår i: Advanced Light Source. - Berkeley : Ernest Orlando Lawrence Berkeley National Laboratory, University of California Berkeley, California, USA. ; , s. 129-132
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Organic conjugated polymers have the electronic structure of semiconductors and can be doped to become good conductors (1). Conjugated polymers are now used as active materials in a wide variety of prototype applications such as light emitting diodes [2] and organic transistors [3,4]. Most of the interesting chemistry and physics of conjugated polymers is associated with the details of the electronic structure at the valence and conduction band edges and, in this connection, various electron spectroscopies can be used as tools for diagnosis of the relevant electronic and geometric properties....
|
|
| 3. |
- Guo, J.-H., et al.
(författare)
-
Resonant and nonresonant x-ray scattering spectra of some poly(phenylenevinylene)s
- 1998
-
Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 108:14, s. 5990-5996
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of some poly(phenylenevinylene)s have been investigated by resonant and nonresonant x-ray inelastic scattering spectroscopies. The nonresonant as well as all resonant spectra for each polymer demonstrate benzene-like features, indicating a local character of the x-ray emission in which the phenyl ring acts as a building block. Theoretical simulations of x-ray energies and intensities taking the repeat unit as a model molecule of the polymer agree with the experimental spectra fairly well. The edges of the occupied bands have been identified in the nonresonant spectra of each polymer. By subtracting the emission energy of the highest occupied molecular orbital in the nonresonant spectrum from the core excitation energy in the resonant spectrum an alternative way to determine the optical band gap is obtained. As for free benzene the outer π band in the polymer spectra show a depletion of the emission going from the nonresonant to the resonant x-ray emission spectra. It is demonstrated that this transition, which is strictly symmetry forbidden for free benzene, becomes effectively forbidden in the polymer case as a result of strong interference effects, and it is argued that this is the general case for resonant x-ray emission of conjugated polymers as far as the frozen orbital approximation holds.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
|
|
| 7. |
|
|
| 8. |
- Zabel, B A, et al.
(författare)
-
Human G protein-coupled receptor GPR-9-6/CC chemokine receptor 9 is selectively expressed on intestinal homing T lymphocytes, mucosal lymphocytes, and thymocytes and is required for thymus-expressed chemokine-mediated chemotaxis
- 1999
-
Ingår i: Journal of Experimental Medicine. - 1540-9538. ; 190:9, s. 1241-1256
-
Tidskriftsartikel (refereegranskat)abstract
- TECK (thymus-expressed chemokine), a recently described CC chemokine expressed in thymus and small intestine, was found to mediate chemotaxis of human G protein-coupled receptor GPR-9-6/L1.2 transfectants. This activity was blocked by anti-GPR-9-6 monoclonal antibody (mAb) 3C3. GPR-9-6 is expressed on a subset of memory alpha4beta7(high) intestinal trafficking CD4 and CD8 lymphocytes. In addition, all intestinal lamina propria and intraepithelial lymphocytes express GPR-9-6. In contrast, GPR-9-6 is not displayed on cutaneous lymphocyte antigen-positive (CLA(+)) memory CD4 and CD8 lymphocytes, which traffic to skin inflammatory sites, or on other systemic alpha4beta7(-)CLA(-) memory CD4/CD8 lymphocytes. The majority of thymocytes also express GPR-9-6, but natural killer cells, monocytes, eosinophils, basophils, and neutrophils are GPR-9-6 negative. Transcripts of GPR-9-6 and TECK are present in both small intestine and thymus. Importantly, the expression profile of GPR-9-6 correlates with migration to TECK of blood T lymphocytes and thymocytes. As migration of these cells is blocked by anti-GPR-9-6 mAb 3C3, we conclude that GPR-9-6 is the principal chemokine receptor for TECK. In agreement with the nomenclature rules for chemokine receptors, we propose the designation CCR-9 for GPR-9-6. The selective expression of TECK and GPR-9-6 in thymus and small intestine implies a dual role for GPR-9-6/CCR-9, both in T cell development and the mucosal immune response.
|
|
| 9. |
|
|
| 10. |
|
|
