Browsing by Issue Date, starting with "2008-09"
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- Structural and Microanalytical Studies of CrO2 Thin Films on c-Sapphire by High Resolution Electron Microscopy MethodsPublication . Ortiz, M. I.; Sousa, P. M.; Ballesteros, C.; Jorge Silvestre, António; Cohen, L. F.; Conde, O.Chromium dioxide (CrO2) has been extensively used in the magnetic recording industry. However, it is its ferromagnetic half-metallic nature that has more recently attracted much attention, primarily for the development of spintronic devices. CrO2 is the only stoichiometric binary oxide theoretically predicted to be fully spin polarized at the Fermi level. It presents a Curie temperature of ∼ 396 K, i.e. well above room temperature, and a magnetic moment of 2 mB per formula unit. However an antiferromagnetic native insulating layer of Cr2O3 is always present on the CrO2 surface which enhances the CrO2 magnetoresistance and might be used as a barrier in magnetic tunnel junctions.
- How foam-like is the shear-induced lamellar phase of an ionic liquid crystal?Publication . Cruz, C.; Godinho, M. H.; Ferreira, A. J.; Kulkarni, P. S.; Afonso, C. A. M.; Teixeira, PauloIn a recent article [ M. H. Godinho et al., Liq. Cryst. 35, 103 ( 2008)] we reported that sheared films of two n-alkylimidazolium salts exhibit liquid crystalline behaviour below their bulk equilibrium freezing temperature. The resulting morphologies are strongly reminiscent of two-dimensional liquid foams: the materials partition into dark domains ( cells) separated by brighter ( birefringent) walls, which are approximately arcs of circle and meet at vertices ("Plateau borders") with three or more sides. Here we investigate whether they satisfy known quantitative results for foams [see, e. g. D. Weaire and S. Hutzler, The Physics of Foams ( Oxford University Press, Oxford, 1999)]. We find that: (i) where three walls meet, they do so at approximately 120 degrees angles, for all times studied; (ii) Lewis's law of linear relation between cell area and number of sides is approximately satisfied at late times; (iii) the morphological patterns coarsen in time, both T1 and T2 processes are observed and, at late times, evolution is consistent with von Neumann's law; and (iv) relatively large numbers of 5-sided cells survive up to fairly late times. Results ( i) and ( iii) suggest that surface tension may play a key role in determining the physics of this system, as it does in low-viscosity liquid foams.
- 5' and 3' UTR thymidylate synthase polymorphisms modulate the risk of colorectal cancer independently of the intake of methyl group donorsPublication . Carmona, Bruno; Guerreiro, Catarina Sousa; Cravo, Marília; Leitão, Carlos Nobre; Brito, MiguelThymidylate synthase, as a rate-limiting step in DNA synthesis, catalyses the conversion of dUMP into dTMP using 5,10-methylenotetrahydrofolate as the methyl donor. Two polymorphisms have been described in this gene: a repeat polymorphism in the 5' promoter enhancer region (3R versus 2R) and a 6 bp deletion in the 3' unstranslated region. Both of these may affect protein levels. The present case control study was aimed at investigating the influence of these two polymorphisms on the development of colorectal cancer (CRC), as well as their potential interaction with folate, vitamin B6 and vitamin B12 intake. A total of 196 cases and 200 controls, matched for age and sex distribution, were included in the study. No association was found between CRC and the 28 bp repeat polymorphism, but it was observed that individuals with the 6 bp/del and del/del genotypes had a significantly lower risk of developing the disease (OR=0.47; 95% CI 0.30-0.72). A combined genotype (2R/2R; 6 bp/del+del/del) was also found, which was associated with an even lower risk of developing of the disease (OR=0.42; 95% CI 0.26-0.69). No significant interaction between these polymorphisms and vitamin intake was observed. These results indicate for the first time that the 6 bp/del allele might be a protective factor in the development of CRC, independent of the intake of methyl group donors.
- Públicos da cultura: o lugar dos estranhosPublication . Matoso, RuiQuando Ortega y Gasset afirma que «viver é estar entregue ao inimigo, ao mundo» (Gasset, 142), numa variação complementar do seu famoso aforismo «o homem é o homem e as suas circunstâncias», dá a entender que não se pode compreender a ipseidade individual (a existência singular e concreta) prescindindo dos contextos e do momento histórico em que se vive, bem como das relações que se estabelecem. Neste caso, acrescenta o filósofo, haveria que substituir o princípio cartesiano resumido no cogito ergo sum (penso, logo existo), e na sua vez afirmar: penso, logo somos, o mundo e eu. A composição social das nossas cidades está em constante mutação, tendo a valorização da “diversidade cultural” assumido, nos últimos anos, uma importância política, retórica e mediática, sem precedentes. É nosso objectivo neste artigo equacionar o seu significado e as suas práticas do lado dos públicos da cultura.
- A obesidadePublication . Verissimo, JorgePor ser sensível às matérias relacionadas com o corpo humano, por via de uma investigação que desenvolvi quanto às suas representações na imagem publicitária, estou, também, mais atento ao corpo do que me está próximo. Neste sentido, a praia é um lugar privilegiado para o observar. E o que nos é dado a ver é, por vezes, alarmante. Vejamos, se em determinados corpos masculinos se destaca a cintura estreita e a ausência de “estômago”; noutros é possível observar o excesso de peso, marcado, principalmente, pelos ombros largos e pela proeminência da barriga.
- A critical chain perspective to support management activities in dynamic production networksPublication . Tenera, Alexandra; Abreu, AntónioCollaborative networks are typically assumed to bring clear benefits and competitive advantage to the participating members. However, as the networks are typically formed by heterogeneous and autonomous enterprises, the development of methodologies that facilitates the management process is an important element for the wide adoption of this paradigm. Departing from a brief presentation of the Critical Chain Project Management approach, the paper introduces this approach to collaborative networks and discusses its potential application in the context of a dynamic production networks. Finally, experimental results based on data from a network in construction industry are presented.
- James Carey and the legacy of Chicago school of sociology on communication and media studiesPublication . Subtil, Filipa Mónica de Brito GonçalvesAlthough the communication issue has won intellectual status in modern thought and in the social research through the sociological school of Chicago, the communication and media studies have tended to neglect, with some exceptions, that crucial contribution. This paper will focus on the way James Carey, one of the most influent American theorists of media and journalism in the second half of XX century, considered, discussed, and critically embodied the reflection about communication in the Chicago School of sociology. By questioning the “standard” history of mass communication research confined to the functionalist and empiricist paradigm of mass communication, Carey points out the importance of reconsidering an argumentative, civic and universalistic conception of communication which was a legacy of Dewey, Cooley, Mead, and Park. Firstly, this paper proposes to show how Carey recovers and re-elaborates this notion to argue that communication is more than transmission of signals and signs. Supported by the Chicago tradition, he defines communication as a life experience found on human quality of intimacy, conversation, and on the understanding that comes from shared experience. Secondly, it presents Carey’s critique to the utopic features of this tradition, especially to the excessive expectations on communication technologies to improve the quality of culture and civic life. Finally, it discusses how Carey brings back the sociological communication concept of Chicago to confront it with a technical conception of communication that distinguishes the present media industry, showing how communication has lost its dimension of communion and sharing, and definitively tangled in a world of sophisticated economical and political strategies.
- Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. Jorge Island, Azores triple junctionPublication . Hildenbrand, Anthony; Madureira, Pedro Miguel; Marques, Fernando Ornelas; Cruz, Inês; Henry, Bernard; Silva, PedroNew K/Ar dating and geochemical analyses have been carried out on the WNW-ESE elongated oceanic island of S. Jorge to reconstruct the volcanic evolution of a linear ridge developed close to the Azores triple junction. We show that S. Jorge sub-aerial construction encompasses the last 1.3 Myr, a time interval far much longer than previously reported. The early development of the ridge involved a sub-aerial building phase exposed in the southeast end of the island and now constrained between 1.32 +/- 0.02 and 1.21 +/- 0.02 Ma. Basic lavas from this older stage are alkaline and enriched in incompatible elements, reflecting partial melting of an enriched mantle source. At least three differentiation cycles from alkaline basalts to mugearites are documented within this stage. The successive episodes of magma rising, storage and evolution suggest an intermittent reopening of the magma feeding system, possibly due to recurrent tensional or trans-tensional tectonic events. Present data show a gap in sub-aerial volcanism before a second main ongoing building phase starting at about 750 ka. Sub-aerial construction of the S. Jorge ridge migrated progressively towards the west, but involved several overlapping volcanic episodes constrained along the main WNW-ESE structural axis of the island. Malic magmas erupted during the second phase have been also generated by partial melting of an enriched mantle source. Trace element data suggest, however, variable and lower degrees of partial melting of a shallower mantle domain, which is interpreted as an increasing control of lithospheric deformation on the genesis and extraction of primitive melts during the last 750 kyr. The multi-stage development of the S. Jorge volcanic ridge over the last 1.3 Myr has most likely been greatly influenced by regional tectonics, controlled by deformation along the diffuse boundary between the Nubian and the Eurasian plates, and the increasing effect of sea-floor spreading at the Mid-Atlantic Ridge.