Browsing by Issue Date, starting with "2013-08"
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- Wireless interrogation of an optically modulated resonant tunnelling diode oscillatorPublication . Cantu, Horacio I.; Salgado, H. M.; Romeira, Bruno; Kelly, Anthony E.; Ironside, C. N.; Figueiredo, Jose M. L.In this work, a resonant tunnelling diode-photo-detector based microwave oscillator is amplitude modulated using an optical signal. The modulated free running oscillator is coupled to an antenna and phase locked by a wireless carrier that allows remote extraction of the information contained in the modulation. An off-the-shelf demodulator has been used to recover the envelope of the baseband data originally contained in the optical signal. Data were successfully transmitted at a rate of 1 MSym/s with a bit error rate below 10-6. (c) 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1728-1730, 2013
- Do "small is beautiful" ao "small is unsustainable"Publication . Sousa, Vanessa Duarte de; Dias, NelsonO presente artigo debruça-se sobre a realidade das actividades económicas de pequena escala em Portugal. as discussões políticas mais recentes têm vindo a colocar “em cima da mesa”, cada vez com maior insistência, a problemática das pequenas e médias empresas. No entanto, como não se ultrapassam as abordagens generalistas, a especificidade das unidades económicas de pequena escala não emerge, sendo por essa via invisibilizada ao nível do pensamento e da acção. Ao longo das próximas páginas serão abordadas as dificuldades enfrentadas por estes microempreendedores, obrigados a respeitar quadros normativos e procedimentos funcionais estipulados para regular a competitividade internacional, mesmo que o seu campo de acção sejam os mercados de proximidade. São os reflexos de um país com “sede” de internacionalização, preocupado com as exportações e o investimento estrangeiro, mas que ao mesmo tempo cilindra as pequenas unidades produtivas nacionais que garantem emprego e produção de riqueza, conduzindo o país a uma dinâmica de empobrecimento.
- PrefacePublication . Mendonca, J. T.; Shukla, P. K.; Eliasson, B.; Rodrigues, J. A.
- Development and validation of an experimental life support system for assessing the effects of global climate change and environmental contamination on estuarine and coastal marine benthic communitiesPublication . Coelho, Francisco J. R. C.; Rocha, Rui J. M.; Pires, Ana C. C.; Ladeiro, Bruno; Castanheira, Jose M.; Costa, Rodrigo; Almeida, Adelaide; Cunha, Angela; Lillebo, Ana Isabel; Ribeiro, Rui; Pereira, Ruth; Lopes, Isabel; Marques, Catarina; Moreira-Santos, Matilde; Calado, Ricardo; Cleary, Daniel F. R.; Gomes, Newton C. M.An experimental life support system (ELSS) was constructed to study the interactive effects of multiple stressors on coastal and estuarine benthic communities, specifically perturbations driven by global climate change and anthropogenic environmental contamination. The ELSS allows researchers to control salinity, pH, temperature, ultraviolet radiation (UVR), tidal rhythms and exposure to selected contaminants. Unlike most microcosms previously described, our system enables true independent replication (including randomization). In addition to this, it can be assembled using commercially available materials and equipment, thereby facilitating the replication of identical experimental setups in different geographical locations. Here, we validate the reproducibility and environmental quality of the system by comparing chemical and biological parameters recorded in our ELSS with those prevalent in the natural environment. Water, sediment microbial community and ragworm (the polychaete Hediste diversicolor) samples were obtained from four microcosms after 57days of operation. In general, average concentrations of dissolved inorganic nutrients (NO3-; NH4+ and PO4-3) in the water column of the ELSS experimental control units were within the range of concentrations recorded in the natural environment. While some shifts in bacterial community composition were observed between in situ and ELSS sediment samples, the relative abundance of most metabolically active bacterial taxa appeared to be stable. In addition, ELSS operation did not significantly affect survival, oxidative stress and neurological biomarkers of the model organism Hediste diversicolor. The validation data indicate that this system can be used to assess independent or interactive effects of climate change and environmental contamination on benthic communities. Researchers will be able to simulate the effects of these stressors on processes driven by microbial communities, sediment and seawater chemistry and to evaluate potential consequences to sediment toxicity using model organisms such as Hediste diversicolor.
- Observations of migrant exchange and mixing in a coral reef fish metapopulation link scales of marine population connectivityPublication . Horne, John B.; van Herwerden, Lynne; Abellana, Sheena; McIlwain, Jennifer L.Much progress has been made toward understanding marine metapopulation dynamics, largely because of multilocus microsatellite surveys able to connect related individuals within the metapopulation. However, most studies are focused on small spatial scales, tens of kilometers, while demographic exchange at larger spatial scales remains poorly documented. Additionally, many small-scale demographic studies conflict with broad-scale phylogeographic patterns concerning levels of marine population connectivity, highlighting a need for data on more intermediate scales. Here, we investigated demographic recruitment processes of a commercially important coral reef fish, the bluespine unicornfish (Naso unicornis) using a suite of mitochondrial DNA (mtDNA) and microsatellite markers. Sampling for this study ranged across the southern Marianas Islands, a linear distance of 250 km and included 386 newly settled postlarval recruits. In contrast with other studies, we report that cohorts of recruits were genetically homogeneous in space and time, with no evidence of temporally stochastic sweepstakes reproduction. The genetic diversity of recruits was high and commensurate with that of the adult population. In addition, there is substantial evidence that 2 recruits, separated by 250 km, were full siblings. This is the largest direct observation of dispersal to date for a coral reef fish. All indications suggest that subpopulations of N. unicornis experience high levels of demographic migrant exchange and metapopulation mixing on a spatial scale of hundreds of kilometers, consistent with high levels of broad-scale genetic connectivity previously reported in this species.
- Computation with perturbed dynamical systemsPublication . Bournez, Olivier; Graca, Daniel S.; Hainry, EmmanuelThis paper analyzes the computational power of dynamical systems robust to infinitesimal perturbations. Previous work on the subject has delved on very specific types of systems. Here we obtain results for broader classes of dynamical systems (including those systems defined by Lipschitz/analytic functions). In particular we show that systems robust to infinitesimal perturbations only recognize recursive languages. We also show the converse direction: every recursive language can be robustly recognized by a computable system. By other words we show that robustness is equivalent to decidability. (C) 2013 Elsevier Inc. All rights reserved.
- Effects of temperature, food type and food concentration on the grazing of the calanoid copepod Centropages chierchiaePublication . Garrido, Susana; Cruz, Joana; Santos, A.M.P.; Re, Pedro; Saiz, EnricLaboratory experiments were conducted to study the combined effect of temperature (8, 13, 19 and 24C), food type and food concentration on the grazing rates of the adult stages of the calanoid copepod Centropages chierchiae. As prey, the diatom Phaeodactylum tricornutum and the dinoflagellate Gymnodinium sp. (both ca. 15 m cell diameter) were used at a range of carbon concentrations similar to the ones experienced in nature (6.4 to 393.8 C L-1). Ingestion rates increased linearly with food concentration and did not differ between prey types. When comparing the effect of temperature, highest clearance and ingestion rates were obtained at 19C, whereas no difference was observed among the other temperatures. Daily rations varied between 1.2 and 183.5 body carbon day(1). Additional experiments were conducted to study the selective feeding behaviour of C. chierchiae when offered a mixture of different prey types. Selective feeding was dependent on food concentration; at low food levels, large cells were selected (Ditylum brightwellii), whereas at medium and high food concentrations no clear selection patterns were observed. In contrast to other studies, no positive selection of dinoflagellates over other algal food was found.
- P-TRAP: a Panicle Trait Phenotyping toolPublication . Al-Tam, Faroq; Adam, Helene; Dos Anjos, António; Lorieux, Mathias; Larmande, Pierre; Ghesquiere, Alain; Jouannic, Stefan; Shahbazkia, Hamid RezaBackground: In crops, inflorescence complexity and the shape and size of the seed are among the most important characters that influence yield. For example, rice panicles vary considerably in the number and order of branches, elongation of the axis, and the shape and size of the seed. Manual low-throughput phenotyping methods are time consuming, and the results are unreliable. However, high-throughput image analysis of the qualitative and quantitative traits of rice panicles is essential for understanding the diversity of the panicle as well as for breeding programs. Results: This paper presents P-TRAP software (Panicle TRAit Phenotyping), a free open source application for high-throughput measurements of panicle architecture and seed-related traits. The software is written in Java and can be used with different platforms (the user-friendly Graphical User Interface (GUI) uses Netbeans Platform 7.3). The application offers three main tools: a tool for the analysis of panicle structure, a spikelet/grain counting tool, and a tool for the analysis of seed shape. The three tools can be used independently or simultaneously for analysis of the same image. Results are then reported in the Extensible Markup Language (XML) and Comma Separated Values (CSV) file formats. Images of rice panicles were used to evaluate the efficiency and robustness of the software. Compared to data obtained by manual processing, P-TRAP produced reliable results in a much shorter time. In addition, manual processing is not repeatable because dry panicles are vulnerable to damage. The software is very useful, practical and collects much more data than human operators. Conclusions: P-TRAP is a new open source software that automatically recognizes the structure of a panicle and the seeds on the panicle in numeric images. The software processes and quantifies several traits related to panicle structure, detects and counts the grains, and measures their shape parameters. In short, P-TRAP offers both efficient results and a user-friendly environment for experiments. The experimental results showed very good accuracy compared to field operator, expert verification and well-known academic methods.
- Small-scale genetic structure of Cerastoderma glaucum in a lagoonal environment: potential significance of habitat discontinuity and unstable population dynamicsPublication . Vergara-Chen, Carlos; Gonzalez-Wangueemert, Mercedes; Marcos, Concepcion; Perez-Ruzafa, AngelEnvironmental heterogeneity in coastal lagoons is expected to facilitate local adaptation in response to different ecological conditions, causing significant genetic structuring within lagoon populations at a small scale and also differentiation between lagoons. However, these patterns and processes of genetic structuring are still poorly understood. The aims of our study were (1) to seek genetic structure at a small scale in Cerastoderma glaucum inside the Mar Menor coastal lagoon using a mitochondrial DNA marker (COI) that has previously detected genetic differentiation inside the lagoon in other species and (2) to evaluate the influence of extreme environmental conditions and habitat discontinuity on its genetic composition. The results indicate high levels of haplotype diversity and low values of nucleotide diversity. COI data provide evidence of significant population differentiation among some localities within the lagoon. Limited gene flow and unstable population dynamics (i.e. fluctuations in population size caused by local extinction and recolonization), probably due to the high environmental heterogeneity, could generate the small-scale genetic divergence detected between populations within the lagoon.