Standard map in magnetized relativistic systems: fixed points and regular acceleration

We investigate the concept of a standard map for the interaction of relativistic particles and electrostatic waves of arbitrary amplitudes, under the action of external magnetic fields. The map is adequate for physical settings where waves and particles interact impulsively, and allows for a series of analytical result to be exactly obtained. Unlike the traditional form of the standard map, the present map is nonlinear in the wave amplitude and displays a series of peculiar properties. Among these properties we discuss the relation involving fixed points of the maps and accelerator regimes.Comment: Work to appear in Phys. Rev. E. 2 figure

Alternate islands of multiple isochronous chains in wave-particle interactions

We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinite number of perturbative terms with the same winding number, which may generate islands in the same region of phase space. As a consequence, the number of isochronous island chains varies as a function of the wave parameters. We observe that in all the resonances, the number of chains is related to the amplitude of the various resonant terms. We determine analytically the position of the periodic points and the number of island chains as a function of the wave number and wave period. Such information is very important when one is concerned with regular particle acceleration, since it is necessary to adjust the initial conditions of the particle to obtain the maximum acceleration.Comment: Submitte

Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include

The multidimensional role of social entrepreneurship: A case study approach within an international project context

Social entrepreneurship creates social value and has a multidimensional impact (e.g. economic, environmental, cultural). This is related to the complexity and multidimensional approaches to current societal problems such as climatic changes and socioeconomic crises. The paper explores this multidimensionality by presenting three Portuguese case studies of social entrepreneurship operating in diverse domains. The study is based on primary and secondary data on the selected social enterprises. The analysis explores the motivations and constraints in forming a social enterprise and the impact of entrepreneurial activity. There is evidence of multiple roles played by these entrepreneurial agents, and, therefore, their critical role in the response to the problems that current societies face.info:eu-repo/semantics/publishedVersio

Aromatic, medicinal, and local herbs: The critical role of networks

The purpose of the communication is to present some research results on the sector of aromatic and medicinal herbs located in different regions of the Portuguese territory. The focus of the presentation is the role of local development associations and networks in the development of the sector. Aromatic and medicinal plants are very important in the Mediterranean diet. Their presence in gourmet food and the recipes of well-known chefs gave an important impulse in the prestige and, therefore, demand of the product. The cultivation of aromatic and medicinal herbs has economic, social, and environmental impacts on the territory. Besides the creation of employment and the possibility of an, principal or complementary, income source, this production provides the improvement of biodiversity and the occupation of rural areas. They are mostly cultivated in small and very small farms, both in developing and developed countries (Kwankhao & Indaratna, 2020; Matthews & Jack, 201; Schunko, et al, 2019; Unati et al, 2016; Yamoah et al, 2014). This characteristic presents many challenges in different dimensions of business development through the value chain, namely commercialization. That is why the connection and the establishment of partnerships with other actors, such as local development associations, and other producers, have an important role, since they provide the scale and critical resources towards the success of this initiatives. The case study selected, EPAM, provides the empirical setting to explore this sector regarding the role of networks. With these goals in mind, the presentation is structured in through the following topics: after the revision of literature, and the design of a conceptual framework, the communication presents the methodological options, and the results. The presentation finishes with the identification of limitations of the research and concluding remarks.info:eu-repo/semantics/publishedVersio

Small, smart and sustainable: Networking to develop the medicinal and aromatic plants value-chain in Portugal

The paper aims to study the use of medicinal and aromatic plants (MAP) farmers’ networking activities to overcome challenges in the development of their business. MAPs are mostly cultivated in small farms located in rural territories. This presents many challenges in different dimensions of business development through the value-chain, namely in commercialization. That is why networking and collaboration with other actors may have an important role, by providing the scale and critical resources towards business success and value-chain sustainable development. The paper draws on a purposefully collected set of data on a network of Portuguese producers of MAP, organized under the EPAM project. The data was collected through a questionnaire and quantitatively analyzed in order to understand: i) how MAP farmers perceive the importance of networks for the development of their businesses? ii) How are networks enabling farmers with different profiles to develop their businesses? The results confirm the importance of networks for the development of these businesses, namely with other firms. However, it is possible to identify some diversity in the assessment of the role of those networks, both by taking into consideration the location of the farms and their positioning in the value-chain. The study contributes to a better understanding of how networking contributes to overcome barriers in the sustainable development of an agri-food value-chain, by stressing a variety of networking proposes and partners and the existence of differences across types of firms.info:eu-repo/semantics/publishedVersio

Critical cities. Learning from extreme urban contexts, paths for sustainable urban planning in New Delhi and beyond

New Delhi is the second largest megacity in the world, housing around 26 million inhabitants, it’s also a city of extremes.1 Uneven growth and social segregation, massive urbanization, environmental threats, lack of public services, infrastructural weaknesses are a daily routine, and not some future dystopian scenario. 2 According to Delhi Master Plan (2021), only 24% of the population lives in considered legal areas, with the remaining 76% of the population inhabiting unauthorized areas, with poor access to basic services such as house, water, electricity, health or education. 3 The majority of urban population seems to have been forgotten across time or doomed to social-spatial exclusion, enunciating an outstanding gap between planning practice and the dynamics and needs of the city. We may question whether the perpetuation of this gap hasn’t been always embedded in planning and policy practice, constituting an echo of political, economic, institutional and scientific ‘influences’ ? from the West to the East or a mirror of the Indian fragmented society. 4 Three urban planning moments will be revisited in this paper, corresponding also to specific historical contexts, urban models, polices and regulations: Colonial planning driven by the interests of the British empire; modernist planning motivated by post-independence democracy; and, more recently, what one may venture to categorize as neoliberal planning, boosted by economic structural adjustments in the 90’s.56 It’s intended to demonstrate the nexus between the exercise of planning and police making and the growing detachment between a ‘planned city’ and an ‘unplanned city’, with its extreme consequences and risks. Finally, the paper presents some concluding remarks on the importance to critically analyse the permeability of concepts, models and practices to external influences, and how urban planning field may be undermined and/or undermining the solving of urban challenges around the World. This paper presents preliminary results of a research exchange at the Centre for the Study of Science Policy, Jawarlal Nehru University (New Delhi) under the European Marie Currie project "Crossing Borders. Knowledge, Innovation and Technology transfer across borders". Main results are based on literature review, consultation of planning/policy tools and the analysis of a set of interviews conducted to researchers from several disciplinary fields and to public institutions related to urban planning.info:eu-repo/semantics/publishedVersio

Milho doce: origem de mutações naturais.

Esta publicação tem como objetivo revisar as principais mutações espontâneas que provocam alterações no conteúdo de açúcares na semente do milho. Estas mutações dão origem ao que conhecemos hoje como milho-doce. Este tipo de milho vem ganhando espaço no Brasil e seu consumo tende a aumentar, à medida que um maior número de híbridos com diferentes combinações de mutações e dosagens alélicas apareçam no mercado, atendendo às diferentes necessidades do consumidor e das indústrias alimentícias.bitstream/item/70062/1/doc-144.pd