50 research outputs found
The role of mixotrophic protists in the biological carbon pump
No full textThe traditional view of the planktonic food web describes consumption of inorganic nutrients by photoautotrophic phytoplankton, which in turn supports zooplankton and ultimately higher trophic levels. Pathways centred on bacteria provide mechanisms for nutrient recycling. This structure lies at the foundation of most models used to explore biogeochemical cycling, functioning of the biological pump, and the impact of climate change on these processes. We suggest an alternative new paradigm, which sees the bulk of the base of this food web supported by protist plankton communities that are mixotrophic – combining phototrophy and phagotrophy within a single cell. The photoautotrophic eukaryotic plankton and their heterotrophic microzooplankton grazers dominate only during the developmental phases of ecosystems (e.g. spring bloom in temperate systems). With their flexible nutrition, mixotrophic protists dominate in more-mature systems (e.g. temperate summer, established eutrophic systems and oligotrophic systems); the more-stable water columns suggested under climate change may also be expected to favour these mixotrophs. We explore how such a predominantly mixotrophic structure affects microbial trophic dynamics and the biological pump. The mixotroph-dominated structure differs fundamentally in its flow of energy and nutrients, with a shortened and potentially more efficient chain from nutrient regeneration to primary production. Furthermore, mixotrophy enables a direct conduit for the support of primary production from bacterial production. We show how the exclusion of an explicit mixotrophic component in studies of the pelagic microbial communities leads to a failure to capture the true dynamics of the carbon flow. In order to prevent a misinterpretation of the full implications of climate change upon biogeochemical cycling and the functioning of the biological pump, we recommend inclusion of multi-nutrient mixotroph models within ecosystem studies
Exploring the distance between nitrogen and phosphorus limitation in mesotrophic surface waters using a sensitive bioassay
No full textThe balance in microbial net consumption of nitrogen and phosphorus was investigated in samples collected in two mesotrophic coastal environments: the Baltic Sea (Tvärminne field station) and the North Sea (Espegrend field station). For this, we have refined a bioassay based on the response in alkaline phosphatase activity (APA) over a matrix of combinations in nitrogen and phosphorus additions. This assay not only provides information on which element (N or P) is the primary limiting nutrient, but also gives a quantitative estimate for the excess of the secondary limiting element (P+ or N+, respectively), as well as the ratio of balanced net consumption of added N and P over short timescales (days). As expected for a Baltic Sea late spring–early summer situation, the Tvärminne assays (n = 5) indicated N limitation with an average P+ = 0.30 ± 0.10 µM-P, when incubated for 4 days. For short incubations (1–2 days), the Espegrend assays indicated P limitation, but the shape of the response surface changed with incubation time, resulting in a drift in parameter estimates toward N limitation. Extrapolating back to zero incubation time gave P limitation with N+ ≈ 0.9 µM-N. The N : P ratio (molar) of nutrient net consumption varied considerably between investigated locations: from 2.3 ± 0.4 in the Tvärminne samples to 13 ± 5 and 32 ± 3 in two samples from Espegrend. Our assays included samples from mesocosm acidification experiments, but statistically significant effects of ocean acidification were not found by this method
Actuation and control for robotic physiotherapy
No full textOver the last few years researchers have developed prototype robots that are capable of administering physiotherapy, however, these devices tend to be complex and
expensive. The use of modem pneumatic servo systems as actuators would make such devices simpler and cheaper. This thesis assesses the feasibility of a pneumatically actuated robotic physiotherapy device through the implementation of force and position control strategies.
Traditional pneumatic servo systems consist of a pneumatic cylinder prone to stiction effects and a single spool valve. Here the performance of modem pneumatic
servo system, consisting of a low friction pneumatic cylinder and two electropneumatic proportional valves has been evaluated. The increased linearity of the modem pneumatic system enabled a self-tuning pole-placement controller to be implemented that would be unsuitable for conventional pneumatic systems. The selftuning pole-placement controller enabled consistent and accurate position control.
Other researchers have achieved force control of pneumatic systems, however their force models are not applicable on this modem configuration. Accurate control of the
servo system force output, while the position of the cylinder piston is fixed, has been achieved through an open-loop force controller, however applications for fixed
position force control are limited. The servo system force output, during motion, has been found to be a function of the piston velocity and input control signal.
A pneumatic robot has been designed and fabricated with a position workspace that enables the average male to perform upper limb reach and retrieve exercises when attached to the robot. The pneumatically actuated robot, combined with a simple three degree-of-freedom force sensor, form a device capable of administering upper-limb robotic physiotherapy. Impedance control has been identified as the most suitable force and position control strategy for implementing physiotherapy.
Applying the impedance control strategy, to a single link of the robot, resulted in accurate implementation of the desired force and position relationship.
Extending the controller to two and three degrees of freedom has resulted in degradation of the controller performance due to limitations of the three degree-offreedom
force sensor. The controller performance is also found to be dependent upon selection of the impedance characteristics. Low stiffness and high damping, along
with high stiffness and high damping have been identified as particular low points in controller performance due to the requirement for the system to provide large forces
with little resulting motion.
It was concluded that the pneumatic robot and impedance control strategy have the potential to administer physiotherapy. However, further work incorporating a force
sensor with greater accuracy that is robust to torque inputs and a rigorous stability analysis would be required before the device could be clinically evaluated
Mediterranean Pelagic Ecosystem Study: Plankton Dynamics
No full textMediterranean Targeted Project (MTP) - MEDIPELAGOS Project, Contract MAS2-CT93-0063, Synthesis of Final Results.-- 12 pages, 1 figuresPeer Reviewe
Bacterioplankton groups involved in the uptake of phosphate and dissolved organic phosphorus in a mesocosm experiment with P-starved Mediterranean waters
No full text20 pages, 8 figures, 1 tableThe use of inorganic phosphate (Pi) and dissolved organic phosphorus (DOP) by different bacterial groups was studied in experimental mesocosms of P-starved eastern Mediterranean waters in the absence (control mesocosms) and presence of additional Pi (P-amended mesocosms). The low Pi turnover times in the control mesocosms and the increase in heterotrophic prokaryotic abundance and production upon Pi addition confirmed that the bacterial community was originally P-limited. The bacterioplankton groups taking up Pi and DOP were identified by means of microautoradiography combined with catalysed reporter deposition fluorescence in situ hybridization. Incubations with leucine were also performed for comparative purposes. All the probe-identified groups showed a high percentage of cells taking up Pi and DOP in the control, P-limited, mesocosms throughout the experiment. However, in response to Pi addition two contrasting scenarios in Pi use were observed: (i) on day 1 of the experiment Pi addition caused a clear reduction in the percentage of SAR11 cells taking up Pi, whereas Gammaproteobacteria, Roseobacter and Bacteroidetes showed similar percentages to the ones in the control mesocosms and (ii) on day 4 of the experiment, probably when the bacterial community had fully responded to the P input, all the probe-identified groups showed low percentages of cells taking up the substrate as compared with the control mesocosms. These differences are likely related to different P requirements among the bacterial groups and point out to the existence of two contrasting strategies in P useThe mesocosm experiment in the Cretacosmos facility was arranged in cooperation by project Nutritunnel financed by the Research Council of Norway and the MESOAQUA EU network. The processing of the samples was supported by the grants FOSMICRO (CTM2009-07679-E), STORM (CTM2009-09352/MAR), SUMMER (CTM2008-03309/MAR) and MALASPINA (CSD2008 – 00077) funded by the Spanish Ministry of Science and Innovation. We thank Irene Forn and Clara Ruiz for their help with the CARDFISH and MARFISH techniques, Iordanis Magiopoulos for performing the flow cytometer analyses and Tatiana Tsagaraki for performing the inorganic nutrient analyses. Marta Sebastián was supported by the Spanish Ministry of Science and Innovation through a
‘Juan de la Cierva’ awardPeer reviewe
Nutrient dynamics mediated through Turbulence And Plankton interactions - (NTAP)
No full textEuropean Conference on Marine Science & Ocean Technology (EurOCEAN 2004): Celebrating European Marine Science, Building the European Research Area, Communicating Marine Science, 10-13 May 2004, Galway, Ireland.-- 2 pages, 1 figurePeer reviewe
A gazetteer and summary of French pottery imported into Scotland c. 1150 to c. 1650 a ceramic contribution to Scotland's economic history Ceramic Resource Disc 3
No full textThe proposal for a series of published inventories, by countries, of all the imported medieval and post medieval pottery recovered from excavations and field walking in Scotland, was advanced on the final day of the Medieval Pottery Research Group’s conference held in Edinburgh in May 2001. Taking on the roll of creating a gazetteer and catalogue of French pottery in Scotland, it was the authors aim to build on the pioneering work of John Hurst and other medieval ceramicists and in the process make a contribution to the ongoing research on identifiable medieval and post-medieval ceramics traded around the North and Irish Sea
Determining the availability of phosphate and glucose for bacteria in P-limited mesocosms of NW Mediterranean surface waters
No full text11 pages, 6 figuresAvailability of phosphate for phytoplankton and bacteria and of glucose for bacteria was studied in mesocosms using NW Mediterranean coastal water with added phosphate, glucose, or a combination of both. We observed an initial increase of bacterial production in all mesocosms, a continuous increase of particulate P only in the P-enriched mesocosms, and a greater accumulation of dissolved organic C in the glucose-enriched mesocosms compared to those enriched by both glucose and P. This suggests that the water used was initially P-starved with a certain pool of degradable organic C available for bacteria. Specific phosphate affinities indicated a P limitation for the bacterial community in all mesocosms. Specific glucose affinities were different between the mesocosms but much lower than the theoretical maximum predicted from the diffusion-limited model. This suggests that the glucose pool was not a strong controlling factor of bacterial growth. In the P-enriched mesocosms, it is indicated that the extent of P limitation shifted from highest to lowest, while the available pool of glucose steadily decreased during the experiment. The explanation suggested for these observations is that phosphate regeneration was enhanced in the plankton food web, by which bacterial carbon demand became higher than the degradable organic C produced in the P-enriched mesocosmsThis work was supported by the EC through project BASICS (Contract: EVK3-CT 2002-00078). T.T. was supported by the EC through project DANLIM (Contract: EVK3-CT-2001-00049). K.S. and J.J. were supported by a project GACR 206/08/0015 and by the CSIC-CAS mobility programPeer reviewe
Does competition for nanomolar phosphate supply explain the predominance of the cyanobacterium Synechococcus ?
No full textInternational audienceExperimental work during a cruise along a W‐E transect in the Mediterranean Sea suggests that (1) orthophosphate concentrations in the upper photic zone show a decreasing trend from the west to the east reaching levels well below 1 nM and (2) microorganisms in the 0.6–2ߝµm size fraction, probably Synechococcus, have, in addition to high affinity for orthophosphate, significantly higher maximum uptake rates than heterotrophic bacteria or eukaryotic algae. These specific advantages concerning orthophosphate uptake at low (<5 nM) as well as at relatively high (5–25 nM) concentrations could explain both general Synechococcus abundance in P‐depleted environments and transient blooms of this species in the open ocean where episodic orthophosphate nanopulse events are likely to occur
Textual and Musical Analysis of the Song by Wervin Panggabean: “Aut Boi Nian, Lupa Ho Amang And Sai Mulak
No full textThis article describes the TEXTUAL AND MUSICAL ANALYSIS OF WERVIN PANGGABEAN'S SONG "AUT BOI NIAN, LUPA HO AMANG AND SAI MULAK. The aim of your research is to discuss the biography of Wervm Panggabean, analyze the textual meaning and analyze the musical structure. The research uses a qualitative method approach using collection techniques Literature studies, interviews, chervant, photos and sura renderings. In describing the analysis of textual meaning, the author uses Bruno Netll's theory and analyzes it using the Weighted Scale method to describe the content contained in these songs, namely, song transcripts, tonality and scale, ritual, tempo, texture, form, progressive chords and melodic contours. Musically, these songs have an A Major scale. Unmik, the song fur Bor Nian which is taken from the film Toba Dream by Viky Suanipar, A Major is also found in the song Lapa Ho Amang performed by Style Vioce, while the A major scale is by Century Tno, A major Terdin notes from A-B-C#-D-E-F-G#-A’ and D Major for the song Sai Mulak, while the D Major scale is for the song Sai Malak, this song is performed by Century Trio D-E-F#-G-A-B-C#-D'. Meanwhile, to analyze the textual meaning contained in the song, the author uses tron semantics and Fentimand Sazzers with a descriptive approach. In Ferdinand Lausvere's theory, fantinya uses a denotand meaning approach and connotative meaning or broad meaning and the largest meaning and adds significant aspects. The haul that was obtained was the song “Aut Boi Nian” which tells the story of a failed Contains about Failed Love, “Lupa Ho Amang” contains a child who doesn't feel grateful to his parents and “Sai Mulak” contains tells the story of a father who is waiting for his son to come home from abroad.147 PagesSkripsi Sarjan
