Extended temporal Lugiato-Lefever equation and the effect of conjugate fields in optical resonator frequency combs

Starting from the infinite-dimensional Ikeda map, we derive an extended temporal Lugiato-Lefever equation that may account for the effects of the conjugate electromagnetic fields (also called `negative frequency fields'). In the presence of nonlinearity in a ring cavity, these fields lead to new forms of modulational instability and resonant radiations. Numerical simulations based on the new extended Lugiato-Lefever model show that the negative-frequency resonant radiations emitted by ultrashort cavity solitons can impact Kerr frequency comb formation in externally pumped temporal optical cavities of small size. Our theory is very general, is not based on the slowly-varying envelope approximation, and the predictions are relevant to all kinds of resonators, such as fiber loops, microrings and microtoroids

Concentrations of available heavy metals in mediterranean agricultural soils and their relation with some soil selected properties: a case study in typical mediterranean soils

The characterization of the content of trace metals in soils is an instrument in many programs of environmental protection, including the establishment of regional-level standards to detect sites affected by contamination. The objectives of the present study were to study the available levels of Cd, Cr, Cu, Ni, Pb, and Zn in surface horizons of agricultural soils in a typical European Mediterranean region, to establish the geochemical baseline concentration (GBC), background level (BL), and reference value (RV) of each of these available metals, and to investigate their possible correlations with soil properties. To establish the GBC and RV values, we used the " standard threshold method". Topsoil samples (0-20 cm) were collected from 630 sites, and extracted with Diethylene Triamine Pentaacetic Acid (DTPA) to determine their available heavy metal concentrations. The GBC values established were: 0.04 to 0.90 mg kg(-1), 0.70 to 2.50 mg kg(-1), 0.10 to 6.30 mg kg(-1), 0.30 to 7.90 mg kg(-1), 0.29 to 4.50 mg kg(-1), and 0.18 to 2.50 mg kg(-1) for Cd, Cr, Cu, Ni, Pb, and Zn, respectively. Soil properties were found to be correlated with the available heavy metal content, suggesting that the enhanced mobility of heavy metals are related to anthropic activities.Centre for Spatial and Organizational Dynamics (CIEO); Foundation for Science and Technology (FCT)info:eu-repo/semantics/publishedVersio

Urban acupuncture as a rural revitalization strategy: the case study of the Northeastern Algarve

As aldeias do Algarve desde cedo se afirmaram como lugares privilegiados de interacção de valores, possuindo no seu património natural e construído, na sua história e na sua cultura, um potencial capaz de criar dinâmicas na paisagem rural e no território. Esta riqueza cultural, económica e social atravessa, contudo, dificuldades resultantes de um modelo de desenvolvimento que desfavorece estes espaços e tende a inviabilizar os sistemas produtivos tradicionais, promovendo uma visível redução dos dinamismos sócio-demográficos e económicos no interior da região. Neste contexto, várias têm sido as medidas e programas propostos nas últimas décadas como objectivo de revitalizar estes espaços através da implementação de políticas activas de qualificação do urbanismo rural e de dinamização económica, social e cultural, que permitam garantir a qualidade de vida das populações, preservando os seus valores e reabilitando, quer as actividades produtivas tradicionais, quer outras compatíveis que possam valorizar a vida da aldeia. No presente artigo aborda-se o “Programa de Revitalização das Aldeias do Algarve” com o objectivo de evidenciar como, a partir da aplicação de um conjunto de acções pontuais e concertadas sobre o território, é possível afirmar as aldeias como espaços onde se pode viver melhor e beneficiar de um padrão residencial de qualidade

The postindustrial landscape of the Arade river mouth, analysing the past envisioning the future...

Ao longo das últimas décadas vários autores têm defendido que a transformação de paisagens industriais e/ou pós-industriais constitui uma ferramenta de planeamento capaz de contribuir para o (re)-desenvolvimento urbano, promovendo a transformação destas paisagens em lugares úteis e com significado sociocultural. De facto, agora que os produtos formais da sociedade industrial parecem ter terminado o seu ciclo produtivo, é cada vez mais reconhecido, que urge modificar aquela que é, ou tem sido, a visão de quem continua a encarar estes espaços como um problema e não como uma oportunidade. Paralelamente a profunda transformação do conceito de património, aliada à progressiva democratização do mesmo, levou a que estas obras arquitectónicas, muitas vezes de elevado valor patrimonial, deixassem de ser vistas como objectos isolados, tornando-se relevantes não só ao nível do conjunto urbano-territorial, mas também ao nível da sua relação com a paisagem e com o contexto sociocultural em que se inserem, fomentando de forma significativa não só a necessidade de preservação, mas também de reutilização destas estruturas, actualmente desactivadas. No presente artigo apresentar-se-á o caso de estudo da paisagem pós-industrial da Foz do Rio Arade, uma área que urge recuperar, e que se abordada de forma apropriada pode contribuir significativamente para uma melhoria do espaço urbano

Super-resonant radiation stimulated by high-harmonics

Solitons propagating in media with higher order dispersion will shed radiation known as dispersive wave or resonant radiation, with applications in frequency broadening, deep UV sources for spectroscopy or simply fundamental studies of soliton physics. Starting from a recently proposed equation that models the behaviour of ultrashort optical pulses in nonlinear materials using the analytic signal, we find that the resonant radiation associated with the third-harmonic generation term of the equation is parametrically stimulated with an unprecedented gain. Resonant radiation levels, typically only a small fraction of the soliton, are now as intense as the soliton itself. The mechanism is quite universal and works also in normal dispersion and with harmonics higher than the third. We report experimental hints of this super-resonant radiation stimulated by the fifth harmonic in diamond

Post-industrial landscapes as renaissance locus: the case study research method

The fact that several countries are now facing various problems produced by landscapes constructed during the modem period [e.g. industrial revolution], currently in complete physical and functional decadency, contributed to enlarge the negative public perception about these spaces. However, this perception associated with the need to protect the environment has been in the last decades the catalyst to the redevelopment and renaissance of these landscapes. Often in advantageous locations near city centres, situated along waterways, supported by existing infrastructure, and adjacent to residential communities, these landscapes are environmentally impaired assets that need to be returned to productive uses, and reintegrated into the surrounding community. The reclamation and conservation of these landscapes constitute, additionally, an important cultural objective, which is inherently sustainable in that it encourages the positive re-use of redundant buildings that are part of our industrial and commercial heritage. This paper addresses the urgent need to reclaim these landscapes, influenced both by two different tendencies connected with the abandonment of industrial landscapes: on the one hand, the urban pressure related to the city's administration and stakeholders' will to urbanize those areas and on the other hand, the increasingly public awareness of the necessity to protect industrial heritage. This paper presents an approach based on the case study research method. This approach and the way it is applied in this paper may be empirically described as the research and analysis of several successful post-industrial landscape reclamation design approaches, in order to build a set of design principles that might inform and serve as a basis to the redevelopment of similar landscapes

Landscape valuation of environmental amenities throughout the application of direct and indirect methods

Landscape design, construction and management should no longer be the result of superficial approaches based exclusively on designers’ and planners’ ideas. This research starts with the assumption that the aesthetic component constitutes an essential attribute for better understanding and evaluating landscapes. This study analyzes the aesthetic quality and economic valuation of the Lower Guadiana river landscape, through the application of direct and indirect landscape evaluation methods. In order to gauge not only experts’ opinion, it is supported by the application of public participation techniques about the opinion and perceptions of the site visitors/users. The present research considered the analysis of six landscape subunits regarding landscape quality, fragility and visual absorption capacity. The obtained results showed that there are significant differences between the perceptions of the general public and experts’ analysis. Touristic Complexes and Golf Courses had high visual quality, while Agricultural and Production Areas had high visual fragility. Moreover, the performed analysis made clear that the combined use of landscape assessment methods is suited to this type of study, since it enables quantifying the value of existence, management and maintenance of a particular environmental assets and/or services.info:eu-repo/semantics/publishedVersio