Heterogeneous distribution of plankton within the mixed layer and its implications for bloom formation in tropical seas

Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioural aggregation. Simulating a mixing event by adding nutrient-rich deep water abruptly triggered dense phytoplankton blooms in the nutrient-poor environment of the upper layer. These findings suggest that vertical structures within the mixed layer provide critical seeding stocks that can rapidly exploit nutrient influx during mixing, leading to winter bloom formation.

Efficacy of sod removal in regenerating fen vegetation for the conservation of the marsh fritillary butterfly Euphydryas aurinia, Montiaghs Moss Nature Reserve, County Antrim, Northern Ireland.

The efficacy of ‘sod removal’ as a fenland restoration technique was tested using an experimental approach at Montiaghs Moss Nature Reserve, Northern Ireland, from 2006 to 2008. The site suffered from rank growth of purple moor-grass Molinia caerulea which was out-competing herbaceous species. Soil was removed up to a depth of 15 cm completely denuding vegetation in the experimental plot exposing bare peat. By July 2007, 15.2% of sod-removal areas were revegetated; by October 2008 cover had risen to 64.6%. Of this cover, purple moor-grass accounted for only 9-11% compared to 78- 79% on control plots. Cover of other rank-forming grass species was also significantly reduced. Sod removal significantly increased the cover of species characteristic of fenlands including sedges Carex spp., rushes Juncus spp., marsh pennywort Hydrocotyle vulgaris and lesser spearwort Ranunculus flammula. It seems likely that sod removal, which lowered the surface of the peat, restored minerotrophic conditions and exposed the historical seed bank stimulating regeneration of some fenland specialists and pioneer species; this resulted in significantly higher species richness on sod removal plots than control plots two years after treatment. There was no demonstrable effect of sod removal on abundance of devil’s-bit scabious Succisa pratensis, the larval food plant of the Annex II listed marsh fritillary butterfly Euphydryas aurinia. We recommend that consideration should be given to artificially seeding devil’s-bit scabious soon after sod removal treatment to promote early recolonisation and to increase plant abundance on the site.

Negative ion enhancement in caesium-seeded hydrogen discharges - a volume or surface effect?

Measurements of plasma parameters, including H- ion densities, made in conjunction with wall temperature, visible and vacuum ultraviolet emission spectroscopy verify that there is little caesium in the plasma volume of the H- ion source. Surface work function measurements indicate that there is significant caesium coverage of the inner walls of the ion source. It is found that, as the work function of a test surface decreases due to caesium seeding, the H- ion fraction in the discharge volume increases. These observations combine to indicate that, in the present source, the H- ion enhancement mechanism is a surface dominated effect. (C) 1999 American Institute of Physics. [S0003- 6951(99)04744-0].

Identifying optimal sites for natural recovery and restoration of impacted biogenic habitats in a special area of conservation using hydrodynamic and habitat suitability modelling

Selection of sites for successful restoration of impacted shellfish populations depends on understanding the dispersion capability and habitat requirements of the species involved. In Strangford Lough, Northern Ireland, the horse mussel (Modiolus modiolus) biogenic reefs cover only a fraction of their historical range with the remaining reefs badly damaged and requiring restoration. Previous experimental trials suggest that translocation of horse mussels accelerates reef recovery and has therefore been proposed as a suitable restoration technique. We used a series of coupled hydrodynamic and particle dispersal models to assess larval dispersion from remnant and translocated populations to identify suitable areas for adult live M. modiolus translocation in Strangford Lough, Northern Ireland. A maximum entropy model (MAXENT) was used to identify if dispersing larvae could reach habitat suitable for adult M. modiolus. From these we predicted if translocated mussels will reseed themselves or be able to act as larval sources for nearby reefs. The dispersal models showed that the remnant M. modiolus populations are largely self-recruiting with little connectivity between them. The majority of larvae settled near the sources and movement was largely dependent on the tides and not influenced by wind or waves. Higher reef elevation resulted in larvae being able to disperse further away from the release point. However, larval numbers away from the source population are likely to be too low for successful recruitment. There was also little connectivity between the Irish Sea and Strangford Lough as any larvae entering the Lough remained predominantly in the Strangford Narrows. The areas covered by these self-seeding populations are suitable for M. modiolus translocation according to the MAXENT model. As a result of this work and in conjunction with other field work we propose a combination of total protection of all remaining larval sources and small scale translocations onto suitable substrata in each of the identified self-recruiting areas.

One-Pot, High-Yield Synthesis of Convex Au Octahedra by H2O2 - Mediated Process In Solution Phase

A simple, non-seeding and high-yield synthesis of convex gold octahedra with size of ca. 50 nm in aqueous solution is described. The octahedral nanoparticles were systematically prepared by reduction of HAuCl4 using ascorbic acid (AA) in the presence of cetyltrimethylammonium bromide (CTAB) as the stabilizing surfactant while concentrations of Au3+ were fixed. The synthesizing process is especially different to other wet synthesis of metallic nanoparticles because it is mediated by H2O2. Mechanism of the H2O2 – mediated process will be described in details. The gold octahedra were shown to be single crystals with all 8 faces belonging to {111} family. Moreover, the single crystalline particles also showed attractive optical properties towards LSPR that should find uses as labels for microscopic imaging, materials for colorimetric biosensings, or nanosensor developments.

Culture and Characterization of Microglia from the Adult Murine Retina

Purpose. To develop a protocol for isolating and culturing murine adult retinal microglia and to characterize the phenotype and function of the cultured cells. Method. Retinal single-cell suspensions were prepared from adult MF1 mice. Culture conditions including culture medium, growth factors, seeding cell density, and purification of microglia from the mixed cultures were optimised. Cultured retinal microglial cells were phenotyped using the surface markers CD45, CD11b, and F4/80. Their ability to secrete proinflammatory cytokines in response to lipopolysaccharide (LPS) stimulation was examined using cytometric bead array (CBA) assay. Results. Higher yield was obtained when retinal single-cell suspension was cultured at the density of cells per cm2 in Dulbecco’s modified Eagle medium (DMEM)/F12 + Glutamax supplement with 20% fetal calf serum (FCS) and 20% L929 supernatant. We identified day 10 to be the optimum day of microglial isolation. Over 98% of the cells isolated were positive for CD45, CD11b, and F4/80. After stimulating with LPS they were able to secrete proinflammatory cytokines such as IL-6 and TNF-α and express CD86, CD40, and MHC-II. Conclusion. We have developed a simple method for isolating and culturing retinal microglia from adult mice.

Dynamics of interacting Dicke model in a coupled-cavity array

We consider the dynamics of an array of mutually interacting cavities, each containing an ensemble of N two-level atoms. By exploring the possibilities offered by ensembles of various dimensions and a range of atom-light and photon-hopping values, we investigate the generation of multisite entanglement, as well as the performance of excitation transfer across the array, resulting from the competition between on-site nonlinearities of the matter-light interaction and intersite photon hopping. In particular, for a three-cavity interacting system it is observed that the initial excitation in the first cavity completely transfers to the ensemble in the third cavity through the hopping of photons between the adjacent cavities. Probabilities of the transfer of excitation of the cavity modes and ensembles exhibit characteristics of fast and slow oscillations governed by coupling and hopping parameters, respectively. In the large-hopping case, by seeding an initial excitation in the cavity at the center of the array, a tripartite W state, as well as a bipartite maximally entangled state, is obtained, depending on the interaction time. Population of the ensemble in a cavity has a positive impact on the rate of excitation transfer between the ensembles and their local cavity modes. In particular, for ensembles of five to seven atoms, tripartite W states can be produced even when the hopping rate is comparable to the cavity-atom coupling rate. A similar behavior of the transfer of excitation is observed for a four-coupled-cavity system with two initial excitations.

Generation of 10μW relativistic surface high-harmonic radiation at a repetition rate of 10 Hz

Experimental results on relativistic surface HHG at a repetition rate of 10 Hz are presented. Average powers in the 10?W range are generated in the spectral range of 51 to 26 nm (24-48 eV). The surface harmonic radiation is produced by focusing the second-harmonic of a high-power laser onto a rotating glass surface to moderately relativistic intensities of 3×10 ¹⁹Wcm ^?2. The harmonic emission exhibits a divergence of 26 mrad. Together with absolute photon numbers recorded by a calibrated spectrometer, this allows for the determination of the extreme ultraviolet (XUV) yield. The pulse energies of individual harmonics are reaching up to the μJ level, equivalent to an efficiency of 10 ^?5. The capability of producing stable and intense high-harmonic radiation from relativistic surface plasmas may facilitate experiments on nonlinear ionization or the seeding of free-electron lasers. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Progress at JET in integrating ITER-relevant core and edge plasmas within the constraints of an ITER-like wall

This paper reports the progress made at JET-ILW on integrating the requirements of the reference ITER baseline scenario with normalized confinement factor of 1, at a normalized pressure of 1.8 together with partially detached divertor whilst maintaining these conditions over many energy confinement times. The 2.5 MA high triangularity ELMy H-modes are studied with two different divertor configurations with D-gas injection and nitrogen seeding. The power load reduction with N seeding is reported. The relationship between an increase in energy confinement and pedestal pressure with triangularity is investigated. The operational space of both plasma configurations is studied together with the ELM energy losses and stability of the pedestal of unseeded and seeded plasmas. The achievement of stationary plasma conditions over many energy confinement times is also reported.

Picosecond metrology of laser-driven proton bursts

Tracking primary radiation-induced processes in matter requires ultrafast sources and high precision timing. While compact laser-driven ion accelerators are seeding the development of novel high instantaneous flux applications, combining the ultrashort ion and laser pulse durations with their inherent synchronicity to trace the real-time evolution of initial damage events has yet to be realized. Here we report on the absolute measurement of proton bursts as short as 3.5±0.7 ps from laser solid target interactions for this purpose. Our results verify that laser-driven ion acceleration can deliver interaction times over a factor of hundred shorter than those of state-of-the-art accelerators optimized for high instantaneous flux. Furthermore, these observations draw ion interaction physics into the field of ultrafast science, opening the opportunity for quantitative comparison with both numerical modelling and the adjacent fields of ultrafast electron and photon interactions in matter.

Development of sialons colloidally processed in aqueous medium

Desenvolveu-se um novo método de processamento coloidal em meio aquoso para consolidar cerâmicos de α-Y-SiAlON, os quais foram sinterizados por prensagem isostática a quente (HIP) e por spark plasma sintering (SPS). Preparou-se com sucesso uma suspensão aquosa de pós precursores de YSiAlON (Si3N4, Al2O3, Y2O3 e AlN), temporariamente estável, usando Dolapix PC21 como dispersante, permitindo a fabricação de pós granulados pela técnica de aspersão-congelamento-liofilização e a consolidação de corpos em verde por enchimento por barbotina. Avaliou-se o efeito do excesso de oxigénio introduzido pelo processamento aquoso no desenvolvimento microestrutural e nas propriedades mecânicas. Os corpos de Y-SiAlON consolidados por enchimento por barbotina e sinterizados por HIP a 1800ºC apresentaram microestruturas e propriedades mecânicas similares a corpos consolidados por prensagem a seco. Estes materiais exibiram densificação completa, dureza Vickers máxima de 2003 e tenacidade à fractura (método SEVNB) máxima de 5.20 MPam1/2. Foi ainda possível estabelecer uma relação estreita entre o aumento do conteúdo em oxigénio das amostras sinterizadas e a diminuição da tenacidade à fractura. Na tentativa de melhorar a tenacidade à fractura dos materiais, procedeu-se à incorporação nas suspensões de sementes de Ca-α-SiAlON de geometria alongada produzidas por síntese por combustão, adicionadas como agentes de reforço. A síntese por combustão realizada em larga escala (cargas até 1 kg) não produziu efeitos negativos óbvios nos produtos da reacção. Investigara-se os efeitos da adição de 5 % em peso de sementes nas propriedades mecânicas e no desenvolvimento microestrutural de amostras densificadas por HIP. Em comparação com os materiais sem sementes, a tenacidade à fractura (método SEVNB) aumentou 13%, mas a dureza Vickers resultou 14,5% inferior. A sinterização por SPS permitiu obter densificação completa a temperaturas tão baixas como 1600ºC a partir dos pós granulados de Y-SiAlON sem a adição extra de Y2O3 para aumentar o teor de fase líquida. Os materiais sinterizados a 1700ºC e 1600ºC mostraram valores máximos de tenacidade à fractura de 4.36 e 4.20 MPam1/2 (método SEVNB), e de dureza Vickers de 2089 e 2084, respectivamente. Esta técnica de sinterização permitiu ainda obter corpos sinterizados translúcidos com uma transmitância máxima de 61% numa amostra de 2mm de espessura. Os corpos translúcidos apresentaram dureza Vickers de 2154 e tenacidade à fractura 3.74 MPam1/2 (método SEVNB).

Multilayered micro/nanocrystalline CVD diamond coatings for biotribology

In the present work multilayered micro/nanocrystalline (MCD/NCD) diamond coatings were developed by Hot Filament Chemical Vapour Deposition (HFCVD). The aim was to minimize the surface roughness with a top NCD layer, to maximize adhesion onto the Si3N4 ceramic substrates with a starting MCD coating and to improve the mechanical resistance by the presence of MCD/NCD interfaces in these composite coatings. This set of features assures high wear resistance and low friction coefficients which, combined to diamond biocompatibility, set this material as ideal for biotribological applications. The deposition parameters of MCD were optimized using the Taguchi method, and two varieties of NCD were used: NCD-1, grown in a methane rich gas phase, and NCD-2 where a third gas, Argon, was added to the gas mixture. The best combination of surface pre-treatments in the Si3N4 substrates is obtained by polishing the substrates with a 15 μm diamond slurry, further dry etching with CF4 plasma for 10 minutes and final ultrasonic seeding in a diamond powder suspension in ethanol for 1 hour. The interfaces of the multilayered CVD diamond films were characterized with high detail using HRTEM, STEM-EDX and EELS. The results show that at the transition from MCD to NCD a thin precursor graphitic film is formed. On the contrary, the transition of the NCD to MCD grade is free of carbon structures other than diamond, as a result of the richer atomic hydrogen content and of the higher substrate temperature for MCD deposition. At those transitions, WC nanoparticles were found due to contamination from the filament, being also present at the first interface of the MCD layer with the silicon nitride substrate. In order to study the adhesion and mechanical resistance of the diamond coatings, indentation and particle jet blasting tests were conducted, as well as tribological experiments with homologous pairs. Indentation tests proved the superior behaviour of the multilayered coatings that attained a load of 800 N without delamination, when compared to the mono and bilayered ones. The multilayered diamond coatings also reveal the best solid particle erosion resistance, due to the MCD/NCD interfaces that act as crack deflectors. These results were confirmed by an analytical model on the stress field distribution based on the von Mises criterion. Regarding the tribological testing under dry sliding, multilayered coatings also exhibit the highest critical load values (200N for Multilayers with NCD-2). Low friction coefficient values in the range μ=0.02- 0.09 and wear coefficient values in the order of ~10-7 mm3 N-1 m-1 were obtained for the ball and flat specimens indicating a mild wear regime. Under lubrication with physiological fluids (HBSS e FBS), lower wear coefficient values ~10-9-10-8 mm3 N-1 m-1) were achieved, governed by the initial surface roughness and the effective contact pressure.

Cultivo da Salicornia ramosissima da Ilha dos Puxadoiros®

O estágio realizado teve como premissa principal perceber o comportamento da planta face ao seu crescimento em altura da própria planta e em número em função de diferentes épocas de sementeira, e de condições de cultivo, nomeadamente de tipos de solo. O trabalho realizado inclui todo o processo desde a apanha, preparação das sementes e dos campos, e a sementeira propriamente dita. Foi acompanhado o crescimento das plantas em 3 alturas diferentes, por contagem do número de plantas e do comprimento das plantas aéreas. Igualmente foram realizadas análises da granulometria dos solos. Determinaram-se os metais pesados nos solos e nas plantas, assim como os açúcares após a hidrólise e derivatização das amostras liofilizadas, tanto da raíz como da parte aérea. Foi possível concluir que a planta nasce com maior abundância em solos franco-siltosos do que em solos franco-arenosos, onde o seu crescimento é muito pobre ou mesmo nulo. Os valores de cádmio e chumbo encontram-se a níveis adequados para o consumo humano. Coloca-se a hipótese da existência de arabinoglucoronoxilanas como constituinte da raiz desta planta.

Temperatura e luz na germinação do endemismo algarvio Tuberaria major

Dissertação mest., Gestão Sustentável de Espaços Rurais, Universidade do Algarve, 2009

Business model analysis of Mobitto: How to solve the chicken and egg problem of a multi-sided platform?

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics