Export 4158 results:
Sort by: Author Title Type [ Year  (Desc)]
2004
Dias, C. J., R. Igreja, R. Marat-Mendes, P. Inacio, J. N. Marat-Mendes, and D. K. Das-Gupta. "Recent advances in ceramic-polymer composite electrets." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 35-40. Abstract
n/a
Dias, C. J., R. Igreja, R. Marat-Mendes, P. Inacio, J. N. Marat-Mendes, and D. K. Das-Gupta. "Recent advances in ceramic-polymer composite electrets." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 35-40. AbstractWebsite
n/a
Martins, M. C., A. M. Costa, J. P. Santos, F. Parente, and P. Indelicato. "Relativistic calculation of two-electron one-photon and hypersatellite transition energies for 12<=Z<=30 elements." Journal of Physics B: Atomic and Molecular Physics. 37 (2004): 3785-3795. AbstractWebsite

Energies of two-electron one-photon transitions from initial double K-hole states were computed using the Dirac–Fock model. The transition energies of competing processes, the Ka hypersatellites, were also computed. The results are compared with experiment and to other theoretical calculations.

Moniz, António Resultados provisórios do exercício Delphi WorTiS (1ª fase)[Provisional results of the 1st round of Delphi WorTiS exercise]. University Library of Munich, Germany, 2004. Abstract

In this working paper are present the main provisional results of the first round of a Delphi survey held in Portugal on the automotive sector. It was done under the WorTiS project, developed by IET – Research Centre on Enterprise and Work Innovation, and financed by the Portuguese Ministry of Science and Technology. The majority of experts consider to have an average of less knowledge in almost all the scenario topics presented. Nevertheless, we considered specially the topics where the experts considered themselves to have some knowledge. There were no “irrelevant” topics considered as such by the expert panel. There are also no topics that is not considered a need for co-operation (that happens in jus tone case). The lack of technological infra-structrures was not considered as an hindered factor for the accomplishement of any scenario. The experts panel considered no other international competence besides US, Japan or Germany in these topics. Although the members of the expert panel were not as many as needed, These situations will be taken into consideration for a second round of the Delphi survey

Pereira, Lu{\'ıs, Hugo Águas, Leandro Raniero, Rui Miguel S. Martins, Elvira Fortunato, and Rodrigo Martins. "Role of substrate on the growth process of polycrystalline silicon thin films by low-pressure chemical vapour deposition." Materials Science Forum. Vol. 455. Trans Tech Publications, 2004. 112-115. Abstract
n/a
Aguas, H., L. Raniero, L. Pereira, A. S. Viana, E. Fortunato, and R. Martins. "Role of the rf frequency on the structure and composition of polymorphous silicon films." Journal of non-crystalline solids. 338 (2004): 183-187. Abstract
n/a
Cunha, P. P., O. Mateus, and MT Antunes. "The sedimentology of the Paimogo dinosaur nest site (Portugal, Upper Jurassic)." 23 rd IAS Meeting of Sedimentology. Coimbra, Portugal 2004. 93. Abstract
n/a
Cunha, P. P., O. Mateus, and MT Antunes. "The sedimentology of the Paimogo dinosaur nest site (Portugal, Upper Jurassic)." 23 rd IAS Meeting of Sedimentology. Coimbra, Portugal 2004. 93. Abstract
n/a
Silva, A., Leandro Raniero, E. Ferreira, Hugo Águas, Lu{\'ıs Pereira, Elvira Fortunato, and Rodrigo Martins. "Silicon etching in CF4/O2 and SF6 atmospheres." Materials Science Forum. Vol. 455. Trans Tech Publications, 2004. 120-123. Abstract
n/a
Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta. "Space charge studies in LDPE using combined isothermal and non-isothermal current measurements." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 25-34. AbstractWebsite

Using a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.

Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta. "Space charge studies in LDPE using combined isothermal and non-isothermal current measurements." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 25-34. AbstractWebsite

Using a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.

Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta. "Space charge studies in LDPE using combined isothermal and non-isothermal current measurements." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 25-34. AbstractWebsite
n/a
Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta. "Space charge studies in LDPE using combined isothermal and non-isothermal current measurements." Ieee Transactions on Dielectrics and Electrical Insulation. 11 (2004): 25-34. Abstract
n/a
Figueiredo, MO, TP Silva, JP Veiga, J. Mirão, and S. Pascarelli. "Speciation of antimony in ancient tile glazes: a XAFS study." 14 th ESRF Users Meetg (2004): 8-13. Abstract
n/a
Raniero, L., N. Martins, P. Canhola, S. Pereira, I. Ferreira, E. Fortunato, and R. Martins. "Spectral response of large area amorphous silicon solar cells." High Temperature Material Processes (An International Quarterly of High-Technology Plasma Processes). 8.2 (2004). Abstract
n/a
Pereira, L., H. Aguas, R. Igreja, R. M. S. Martins, N. Nedev, L. Raniero, E. Fortunato, and R. Martins. "Sputtering preparation of silicon nitride thin films for gate dielectric applications." Advanced Materials Forum Ii. Eds. R. Martins, E. Fortunato, I. Ferreira, and C. Dias. Vol. 455-456. Materials Science Forum, 455-456. 2004. 69-72. Abstract
n/a
Pereira, Lu{\'ıs, Hugo Águas, Rui Igreja, Rui Miguel S. Martins, N. Nedev, Leandro Raniero, Elvira Fortunato, and Rodrigo Martins. "Sputtering preparation of silicon nitride thin films for gate dielectric applications." Materials Science Forum. Vol. 455. Trans Tech Publications, 2004. 69-72. Abstract
n/a
Dias, JM, T. Alves, C. Bonifacio, AS Pereira, J. Trincao, D. Bourgeois, I. Moura, and MJ Romao. "Structural basis for the mechanism of Ca2+ activation of the di-heme cytochrome c peroxidase from Pseudomonas nautica 617." Structure. 12 (2004): 961-973. AbstractWebsite

Cytochrome c peroxidase (CCP) catalyses the reduction of H2O2 to H2O, an important step in the cellular detoxification process. The crystal structure of the di-heme CCP from Pseudomonas nautica 617 was obtained in two different conformations in a redox state with the electron transfer heme reduced. Form IN, obtained at pH 4.0, does not contain Ca2+ and was refined at 2.2 Angstrom resolution. This inactive form presents a closed conformation where the peroxidatic heme adopts a six-ligand coordination, hindering the peroxidatic reaction from taking place. Form OUT is Ca2+ dependent and was crystallized at pH 5.3 and refined at 2.4 Angstrom resolution. This active form shows an open conformation, with release of the distal histidine (His71) ligand, providing peroxide access to the active site. This is the first time that the active and inactive states are reported for a di-heme peroxidase.

Dyke, J. M., G. Levita, A. Morris, J. S. Ogden, A. A. Dias, M. Algarra, J. P. Santos, M. L. Costa, P. Rodrigues, and M. T. Barros. "A Study of the Thermal Decomposition of 2-Azidoacetamide by Ultraviolet Photoelectron Spectroscopy and Matrix-Isolation Infrared Spectroscopy:  Identification of the Imine Intermediate H2NCOCHNH." The Journal of Physical Chemistry A. 108 (2004): 5299-5307. AbstractWebsite

The thermal decomposition of 2-azidoacetamide (N3CH2CONH2) has been studied by matrix-isolation infrared spectroscopy and real-time ultraviolet photoelectron spectroscopy. N2, CH2NH, HNCO, CO, NH3, and HCN are observed as high-temperature decomposition products, while at lower temperatures, the novel imine intermediate H2NCOCHNH is observed in the matrix-isolation IR experiments. The identity of this intermediate is confirmed both by ab initio molecular orbital calculations of its IR spectrum and by the temperature dependence and distribution of products in the photoelectron spectroscopy (PES) and IR studies. Mechanisms are proposed for the formation and decomposition of the intermediate consistent both with the observed results and with estimated activation energies based on pathway calculations.

Borges, J. P., M. H. Godinho, AF Martins, DF Stamatialis, M. N. de Pinho, and M. N. Belgacem. "Tensile properties of cellulose fiber reinforced hydroxypropylcellulose films." Polymer composites. 25.1 (2004): 102-110. Abstract
n/a
Martins, Rodrigo, Elvira Fortunato, P. Nunes, I. Ferreira, A. Marques, M. Bender, N. Katsarakis, V. Cimalla, and G. Kiriakidis. "Zinc oxide as an ozone sensor." Journal of Applied Physics. 96.3 (2004): 1398-1408. Abstract
n/a
Martins, R.a, Fortunato Nunes Ferreira Marques Bender Katsarakis Cimalla Kiriakidis E. a P. a. "Zinc oxide as an ozone sensor." Journal of Applied Physics. 96 (2004): 1398-1408. AbstractWebsite

A study of intrinsic zinc oxide thin film as ozone sensor based on the ultraviolet (UV) photoreduction and subsequent ozone re oxidation of zinc oxide as a fully reversible process was presented. It was found that the film described were produced by spray pyrolysis, dc and rf magnetron sputtering. The dc resistivity of the films changed more than eight orders of magnitude when exposed to an UV dose of 4 mW/cm2. Analysis shows that the porous and textured zinc oxide films produced by spray pyrolysis at low substrate exhibit an excellent ac impedance response.

Silva, Rui Jorge C., Francisco Manuel Braz Fernandes, LuÍs Pereira, António Marques, Isabel Ferreira, Rodrigo Martins, Hugo Águas, Elvira Fortunato, V. Assunção, and Alexandra Gonçalves. "ZnO: Ga thin films produced by RF sputtering at room temperature: Effect of the power density." Materials Science Forum. 455 (2004): 12-15. Abstract
n/a
Fortunato, Elvira, V. Assuncao, António Marques, Alexandra Gonçalves, Hugo Águas, Lu{\'ıs Pereira, Isabel Ferreira, Francisco Manuel Braz Fernandes, Rui Jorge C. Silva, and Rodrigo Martins. "ZnO: Ga thin films produced by RF sputtering at room temperature: Effect of the power density." Materials Science Forum. Vol. 455. Trans Tech Publications, 2004. 12-15. Abstract
n/a
Barbosa, J., O. M. N. D. Teodoro, A. M. C. Moutinho, S. Ribeiro, and C. Monteiro. "{Characterization of TiAl Alloys by Secondary Ion Mass Spectrometry}." Materials science forum. 455-456 (2004): 653-656. Abstract

Titanium aluminides are arising as a valuable alternative to superalloys in applications where the ratio resistance/density is important. Together with excellent mechanical and corrosion properties at high temperatures, such characteristics are very attractive for applications in the aeronautical, aerospace and automotive industries. However, the current high selling price, due to high costs of production and raw materials and the need of very specific equipment, are limitative factors for further applications. With the end of the cold war, and the decrease of traditional markets of TiAl, the strategy to develop other applications, strongly depends on the decrease of production costs. An alternative to the present production routes might be the use of traditional casting techniques, by induction melting of the alloy in a ceramic crucible and pouring into ceramic moulds, made by the investment casting process. However, due to the high reactivity of Ti alloys, the use of traditional ceramic materials cannot be used, as they lead to oxide formation and oxygen pick up both from the crucible and the moulding materials. In this work, the relative oxygen concentration of Ti-48Al castings was measured by SIMS ó Secondary Ion Mass Spectrometry. This technique provides a direct measurement of the isotopic composition with high sensitivity. The cylindrical samples were specially prepared to allow the analysis of the area close to the border. Oxygen profiles were acquired for samples obtained with different mould materials. The comparison of such profiles with hardness ones gives insight in the role of the oxygen concentration in the properties of the alloy and in the choice of the most suitable materials for TiAl production