Development and characterisation of a near-infrared femtosecond optical parametric oscillator frequency comb

This thesis describes a 280 MHz MgO:PPLN-based optical parametric oscillator (OPO) synchronously pumped by a 50 fs Ti:sapphire laser to produce ultrafast pulses in the near-infrared. The OPO tuned over a wavelength range from 1450 - 1550 nm and 1624 - 1750 nm for the signal and idler respectively. The carrier-envelope-offset (CEO) frequency of the signal pulses was stabilised to a 10 MHz reference frequency without f-2f self-referencing, with an RMS phase variation of 0.56 rad over an observation time of 1 second. The relative intensity noise was measured for the CEO-stabilised OPO over an observation time of 64 seconds as 0.04%. The repetition frequency of the OPO was stabilised to 280 MHz using a frequency synthesiser at the eighth harmonic (2.24 GHz). This locking loop had an RMS phase variation of 0.98 mrad over a 1 second observation time. The CEO- and repetition frequencies were then locked simultaneously to a synthesiser referenced to a Rb-disciplined source, to generate a fully stabilised 1.5 μm frequency comb with an absolute uncertainty in comb mode position of 110 Hz. The upper limit for the fractional instability for a comb mode at 200 THz was found to be 2 x 10-11, limited by the stability of the Rb reference. A five-fold increase in comb mode spacing to 1.4 GHz was demonstrated with the stabilised frequency comb. This was achieved using a passive filter cavity, stabilised to a transmission peak via dither locking. The FWHM bandwidth of the optical spectrum for the filtered frequency comb was reduced to 8 nm, however no increase in comb linewidth was observed. An additional experiment was carried out where an external cavity diode laser was frequency-stabilised to a saturated absorption peak in Rb at 780.2 nm using dither locking, providing an optical frequency reference for future OPO frequency combs

Combining new and old: Emergent business models in the food system transition

The research has been developed within a research project on Spatial Planning for Change (SPLACH) through an interdisciplinary approach. The analysis addresses food system’s transition in a specific territory, the Lisbon Metropolitan Area (LMA). The transition of food systems towards a sustainable model has been under analysis and debate. This transition is related with structural changes, namely the emphasis on local production, short supply chains, and the preference for organic products. The shift of the agri-food system is taking place through the creation of entirely new businesses and the shift of individual farms towards organic production. In both cases, the new enterprises resort to a combination of old agricultural knowledge and techniques, new scientific knowledge regarding productive methods and new technological platforms for advertising and commercialization. These mixed sources permit the creation of interesting forms of new business models, combining old and new knowledge and practices. In addition to the agriculture domain, they exemplify how traditional industries can absorb/generate innovation, at technological and organizational levels, and become in line with the new knowledge-based era. The study has three main objectives: to identify and analyze the emerging agri-food businesses in LMA; to characterize business models (BM) changes within the transition dynamics towards sustainability; to reflect on the challenges presented by the food system characteristics, in terms of sustainable BM; and to demonstrate that BM specificity – combining new and old knowledge and practices - is closely related to the characteristics of the food system. The paper presents results of the research on the emergence of a new business models, focusing on the case of an organic food production innovative initiative in the LMA, Quinta do Oeste.info:eu-repo/semantics/publishedVersio

Sustainable food systems: how important are bottom-up innovative experiments?

The paper aims to analyse sustainable innovations in food production, commercialization and consumption, notably in the form of new production practices, new means of commercialization and new patterns of consumer behaviour. The main goal is to determine the importance of these recent experiments in the shift towards a more sustainable sociotechnical food system in Portugal, in a comparative perspective. In fact, there have been social, technological and organizational innovations in the food system in Portugal: novel forms of organic food production; new specialized retail chains; the transformation of food departments in large stores; and the creation of short food supply chains. These experiments – innovations deployed in “niches”, or protected spaces -, may become more widely adopted depending on their degree of compatibility with the dominant regime or, conversely, their ability to substitute the dominant regime (Ingram et al, 2015). Tensions at the mainstream regime (Smith, 2016) or pressures exerted by the landscape (Geels, 2004) may boost the diffusion of these innovations, favouring a complex transition process. When developing initiatives to achieve a sustainable food system, the role played by institutions (local and national authorities and legal framework) is crucial, as is the involvement of a wide range of actors (e.g., farmers, food processing companies, retailers and consumers). New social practices are crucial to this shift, due to centrality of consumers in this shift (Spaargaren, 2011). Policies may support or hinder the emergence and deployment of experiments in the form of new products, processes, business models and practices. The theoretical framework draws on niche strategic management (Smith, 2006), sustainable transitions multilevel approach (Geels, 2004) and social practices approach (Spaargaren, 2011). The paper aims to contribute to the literature by making a critical assessment of the impact of these experiments on the transition in the food system in Portugal, taking into account successful cases reported in the literature. It also aims to contribute to policy formulation regarding a sustainable food systeminfo:eu-repo/semantics/acceptedVersio

The transition of the agro-food system: lessons from organic farming in the Lisbon Metropolitan Area

The paper presents a study on the transition of the agro-food system in Portugal through the analysis of case studies in the Lisbon Metropolitan Area. The theoretical framework draws on the literature on the transition of sociotechnical systems, taking into account the multidimensional nature of the food system (ecological, environmental, socioeconomic and cultural). Social and institutional innovation, technological innovation, public policy impact, and the interactions with the dominant regime are the main dimensions guiding the study of the organic farming initiatives. We identified the supportive policy measures, the role of producers’ networks, the relevance of values, and the obstacles and challenges these initiatives face in their growth process. While the results are in line with the theoretical debate, they also provide new insights on the selection environment, the networks’ dual nature and the existence of different development paths within the organic food niche. One of the main conclusions is that organic farmers perceive the regulatory framework as unfair relative to that of conventional agriculture. Therefore, it is crucial to change this framework to speed up the transition of the agro-food system in Portugal and at the European level.info:eu-repo/semantics/publishedVersio

The importance of interdisciplinary approach to urban agriculture and transitions in food systems: Research on Lisbon Metropolitan Area

Metropolitan areas are strategic territories in the research on ‘urban agriculture, food and food systems’. Land use categories and farm related activities constitute major indicators in this research. One of the main characteristics of periurban areas is the complementary nature of the relations between urban and rural systems. The paper presents and discusses the main findings of two research projects conducted in Lisbon Metropolitan Area, in relation with urban agriculture and food and the transition of the food sociotechnical system. This presentation and further discussion highlights the adequacy of interdisciplinary approaches regarding ‘Connections and missing links within urban agriculture, food and food systems’.info:eu-repo/semantics/publishedVersio

Organizações de economia social: coexistência, exemplo ou alternativa?

A experiência de investigação em projectos no âmbito da economia social traduziu-se numa problematização dirigida às organizações que a integram e que as autoras do texto desenvolvem a partir dos seguintes vectores: i) o desafio relacionado com a estruturação de novas formas de relação entre o económico e o social dando prioridade às pessoas sobre o capital, à utilidade social e ao interesse coletivo sobre o interesse particular e trabalhando com os valores da solidariedade, da cooperação, da ajuda mútua, da equidade e da justiça social; ii) a forma como estas organizações definem a sua identidade face a uma economia de mercado e a procura de alternativas ao modelo socioeconómico dominante; iii) a refundação de modelos organizacionais onde decisores, trabalhadores e clientes actuem inspirados em culturas organizacionais que valorizavam o lugar dos atores na mudança social, o exercício da cidadania e a ação colectiva. As autoras concluem que a economia social poderá fornecer alguns princípios e regras para a construção de um ponto de partida para pensar de outra forma o desenvolvimento sustentável e uma economia socialmente responsável.FC

Frustration in fuzzy protein complexes leads to interaction versatility

Disordered proteins frequently serve as interaction hubs involving a constrained variety of partners. Complexes with different partners frequently exhibit distinct binding modes, involving regions that remain disordered in the bound state. While the conformational properties of disordered proteins are well-characterized in their free states, less is known about the molecular mechanisms by which specificity can be achieved not with one but with multiple partners. Using the energy landscape theory concept of protein frustration, we demonstrate that complexes of disordered proteins exhibit a high degree of local frustration, especically at the binding interface. These suboptimal interactions lead to the possibility of multiple bound substates, each displaying distinct frustration patterns, which are differently populated in complexes with different partners. These results explain how specificity of disordered proteins can be achieved without a single common bound conformation and how the confliict between different interactions can be used to control the binding to multiple partners

Spin physics at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)

We outline the opportunities for spin physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton LHC beam extracted by a bent crystal. In particular, we focus on the study of single transverse spin asymetries with the polarisation of the target.Comment: Contributed to the 20th International Spin Physics Symposium, SPIN2012, 17-22 September 2012, Dubna, Russia, 4 pages, LaTe

Prospectives for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC

We argue that the concept of a multi-purpose fixed-target experiment with the proton or lead-ion LHC beams extracted by a bent crystal would offer a number of ground-breaking precision-physics opportunities. The multi-TeV LHC beams will allow for the most energetic fixed-target experiments ever performed. The fixed-target mode has the advantage of allowing for high luminosities, spin measurements with a polarised target, and access over the full backward rapidity domain --uncharted until now-- up to x_F ~ -1.Comment: 6 pages, 1 table, LaTeX. Proceedings of the 36th International Conference on High Energy Physics (ICHEP2012), 4-11 July 2012, Melbourne, Australi

From expert to data-driven biodiversity knowledge: assessing ecosystem irreplaceability with IUCN red list data for freshwater fish

Critical as they are for humans and nature, freshwater ecosystems are threatened-but the extent and depth of these threats are not well understood, especially if essential biodiversity data are lacking. Any policy aimed at protecting such ecosystems must first assess the threat factors and the potential harm, well before proposing conservation measures such as the creation and development of Protected Areas (PAs). These assessments must be done using a deep and sound knowledge of the actual and potential biodiversity variables. Freshwater ecosystems have been largely neglected in traditional PA design and management (Abell et al. 2007), be it for scarcity of biodiversity data, or for more perception-related reasons such as visibility and accessibility driving the allocation of conservation resources to more data-rich environments