RCAAP Repository

This paper addresses the strategies adopted by science-based start-ups to gain access to knowledge resources at different spatial levels. The goal of the paper is to investigate the presence and relative importance of ties endowed with different types of proximity in firms’ knowledge networks, as well as the role played by non-geographical proximity in gaining access to knowledge sources, both located nearby and at a distance. For this purpose we develop an analytical framework that permits to distinguish between two dimensions of proximity: geographical, associated with the spatial location of the actor; relational, associated with the origin of the tie – leading to different modes of proximity that are further linked with modes of knowledge access (formal or informal). We also develop a methodology to reconstruct the knowledge networks, permitting to identify origin, location and nature of the ties and to position them along modes of proximity. The results show that the incidence and mix of these modes of proximity vary in firms’ individual networks, being possible to identify different patterns of knowledge access. But they also uncover the overall relevance of “relational proximity”, whether or not coexisting with geographical proximity and often compensating for its absence. The paper contributes to our understanding of knowledge access strategies of science-based start-ups and uncovers the spatial spanning role played by the entrepreneurs’ personal networks.

The paper investigates the strategic choices made by young science-based firms’ regarding the selection of knowledge sources. Drawing on two streams of research – on alliances and on social networks – two different dimensions of this strategy are considered: the activation of the entrepreneurs’ social capital (versus the intentional inclusion of new knowledge sources) and the persistence of ties from start-up to the early growth phase. The data collected for a subset of the Portuguese biotechnology sector are analysed with a view to answer to four research questions: i) To what do extent firms’ rely on entrepreneurs’ personal networks, activating their social capital to access scientific and technological knowledge at start-up; ii) To what extent are new actors added to knowledge networks at start-up; iii) Are there differences between existing and new ties in terms of strength and formalisation?; iv) Is there tie persistence in knowledge networks between the start-up and the early growth phases? The results obtained confirm the consideration of the strategies underlying network building is vital for an understanding of the configuration of young science-based firms’ knowledge networks. They reveal the existence of different network building strategies and appear to indicate a tendency for continuity of attitudes over the companies’ life. They also suggest that differences in the network building strategies may be the behind the somewhat contradictory results presented in the literature about the network configuration that is more favourable for innovation

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In this paper some results on the application of four N,N’-tetrasubstituted malonamide derivatives for the extraction and separation of platinum-group metals (PGMs) are presented. The above mentioned extractants were specifically synthesized in order to evaluate their efficiency for the extraction of a specific metal, or group of metals, from aqueous chloride matrices. Different behaviours were obtained towards platinum(IV) and/or palladium(II) extraction, all the N,N’-tetrasubstituted malonamide derivatives allowing the mutual separation of the two metal ions, depending on the HCl concentration. Generally, extraction experiments were carried out involving initial aqueous phases containing 100 mg/L of each metal isolate, in varying 1M to 8M HCl concentration ranges, and 0.05M extractant in 1,2- dichloroethane solutions. From the preliminary results obtained, one can conclude that HCl concentrations and the structure of the malonamide derivative play a crucial role on the efficiency shown for Pt(IV) and/or Pd(II) extraction. The efficiency of the stripping stage of the loaded organic phases is variable, depending on the N,N’-tetrasubstituted malonamide derivative, as well as on the metal ion involved; for Pt(IV), distilled water and 1M HCl were generally successful, whereas for Pd(II), thiourea in HCl gave better results. The overall data already achieved suggest that these extractants may be good candidates for further evaluation in PGMs separations from real solutions resulting from recycling processes.

A cortiça é um recurso natural da maior importância para o nosso País, qualquer que seja o ponto de vista: económico, ambiental, social. O sector corticeiro é um dos "clusters" de maior interesse a desenvolver e apoiar futuramente no nosso País, podendo mesmo ser apontado como um dos desígnios nacionais.

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In this study, the critical milling behaviour of Ni-Ti powder mixtures was evaluated in relation to the effect of atmospheric gases, more specifically to oxygen and nitrogen. Within the experimental conditions used, it is shown that both gases play an important role in the alloying process and that not only oxygen gas reacts with the mechanically alloyed powders but also nitrogen. The most effective mixing occurred for the mixtures with the highest contaminant contents.

This paper presents laboratory results of biological production of hydrogen by photoautrotophic cyanobacterium Anabaena sp. Additional hydrogen production from residual Cyanobacteria fermentation was achieved by Enterobacter aerogenes bacteria. The authors evaluated the yield of H2 production, the energy consumption and CO2 emissions and the technological bottlenecks and possible improvements of the whole energy and CO2 emission chain. The authors did not attempt to extrapolate the results to an industrial scale, but to highlight the processes that need further optimization. The experiments showed that the production of hydrogen from cyanobacteria Anabaena sp. is technically viable. The hydrogen yield for this case was 0.0114 kgH2/kgbiomass which had a rough energy consumption of 1538 MJ/MJH2 and produced 114640 gCO2/MJH2. The use of phototrophic residual cyanobacteria as a substrate in a dark-fermentation process increased the hydrogen yield by 8.1% but consumed 12.0% more of energy and produced 12.1% more of CO2 showing that although the process increased the overall efficiency of hydrogen production it was not a viable energy and CO2 emission solution. To make cyanobacteria-based biofuel production energy and environmentally relevant, efforts should be made to improve the hydrogen yield to values which are more competitive with glucose yields (0.1 kgH2/kgbiomass). This could be achieved through the use of electricity with at least 80% of renewables and eliminating the unessential processes (e.g.pre-concentration centrifugation).

CdTe nano-structures with diameter of ∼100 nm and variable length (200–600 nm) were fabricated on glass substrates covered with conductive buffer layers such as NiCr, ZAO (ZnO:Al2O3 + Ta2O5) or TiPd alloys. The fabrication process consisted of the starting vapour deposition of metal catalyst dropped layer followed by the isothermal catalyst-prompted vapour growth of CdTe nano-structured layer of controllable shape and surface filling. The effect of buffer layers on the crystallographic orientation and thickness of CdTe nano-structured layers is investigated by means of IBA techniques, SEM and X-ray diffraction. It was shown that the formed CdTe nano-layers have a cubic structure, mainly oriented towards the [1 1 1] crystallographic direction, except for those grown on ZAO layer where the X-ray diffraction signal is very weak to be associated to any crystallographic form. The RBS spectra recorded on different areas of each sample type showed an almost constant thickness and SEM images revealed an homogeneous and dense distribution of the structures. It was also possible to study the first stage of the nano-structures grown on the Bi2Te3 seeds.

The study of exhaled breath condensate (EBC) obtained by cooling exhaled air under conditions of spontaneous breathing is considered one of the areas with higher interest in respiratory health research. The use of EBC for elemental determination in occupational exposure requires a standard methodological procedure to implement its practice in occupational studies. EBC is an inhomogeneous sample with organic and particulate matter in suspension, which may hamper analytical results reliability. Total reflection X-ray fluorescence and inductive coupled-plasma mass spectrometry (ICP-MS) techniques were chosen as both are multielemental, require small sample volumes and have appropriate detection limits. Estimation of the overall uncertainty in both techniques was carried out using a pool of EBC collected from a group of workers of a lead processing industry to perform precision and trueness studies for K, Mn, Cu, Cd, Sb and Pb. Precision was estimated in terms of repeatability using the native EBC sample pool and trueness in terms of recovery obtained from spiking aliquots of the EBC pool with K, Mn, Cu, Cd, Sb and Pb at different concentrations. Recovery was the most significant contribution to total uncertainty. The overall uncertainties obtained for ICP-MS enabled to discriminate between groups of individuals exposed to different levels of contaminants. Therefore EBC proved to be useful in human biomonitoring.

A brief quasi-historical survey is presented on the primary joint efforts developed by Portuguese researchers towards the use of synchrotron radiation at European Instrumental Facilities, emphasizing some original contributions and mentioning a few decisive steps towards the adhesion of Portugal to the European Synchrotron Research Facility (ESRF, Grenoble/France).

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Mechanical properties of La9.33Si2Ge4O26 prepared by mechanical alloying and subsequent sintering at 1300–1400 °C for 1 h were evaluated. Hardness and Young's modulus values in the range 7.3–9.6 GPa and 106–135 GPa, respectively, were obtained from nanohardness tests. The fracture toughness values derived from the Palmqvist method varied between 3.5 and 3.9 MPa m1/2 from classical microindentation test with an indentation load of 9.8 N. Yield stress (σy) was determined by inverse analysis from microhardness tests. The maximum value of σy (1829 MPa) was obtained for the sample sintered at 1400 °C showing the highest density (5.42 g/cm3).

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Resulting from growing concerns on climate change and resources depletion, biomass has gained increased importance. Security of supply, better environment and economic development, as worldwide goals, are usually drivers for economic growth. Technology developments have adequately not responded to challenges to diversify resources to substitute carbon-intensive fossil fuels at competitive prices. State-of-the-art energy technologies, although advanced, are facing constraints, justifying icreasing effosts in demonstrating efficient and more environmentally friendly tecnhologies.

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