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Search Results: 1 - 10 of 465893 matches for " Catherine A. Pfister "
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Carbon System Measurements and Potential Climatic Drivers at a Site of Rapidly Declining Ocean pH
J. Timothy Wootton, Catherine A. Pfister
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0053396
Abstract: We explored changes in ocean pH in coastal Washington state, USA, by extending a decadal-scale pH data series, by reporting independent measures of dissolved inorganic carbon (DIC), spectrophotometric pH, and total alkalinity (TA), by exploring pH patterns over larger spatial scales, and by probing for long-term trends in environmental variables reflecting potentially important drivers of pH. We found that pH continued to decline in this area at a rapid rate, that pH exhibited high natural variability within years, that our measurements of pH corresponded well to spectrophotometric pH measures and expected pH calculated from DIC/TA, and that TA estimates based on salinity predicted well actual alkalinity. Multiple datasets reflecting upwelling, including water temperature, nutrient levels, phytoplankton abundance, the NOAA upwelling index, and data on local wind patterns showed no consistent trends over the period of our study. Multiple datasets reflecting precipitation change and freshwater runoff, including precipitation records, local and regional river discharge, salinity, nitrate and sulfate in rainwater, and dissolved organic carbon (DOC) in rivers also showed no consistent trends over time. Dissolved oxygen did not decline over time, indicating that long-term changes did not result from shifts in contributions of respiration to pH levels. These tests of multiple potential drivers of the observed rapid rate of pH decline indicate a primary role for inorganic carbon and suggest that geochemical models of coastal ocean carbon fluxes need increased investigation.
Metagenomic Profiling of a Microbial Assemblage Associated with the California Mussel: A Node in Networks of Carbon and Nitrogen Cycling
Catherine A. Pfister,Folker Meyer,Dionysios A. Antonopoulos
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0010518
Abstract: Mussels are conspicuous and often abundant members of rocky shores and may constitute an important site for the nitrogen cycle due to their feeding and excretion activities. We used shotgun metagenomics of the microbial community associated with the surface of mussels (Mytilus californianus) on Tatoosh Island in Washington state to test whether there is a nitrogen-based microbial assemblage associated with mussels. Analyses of both tidepool mussels and those on emergent benches revealed a diverse community of Bacteria and Archaea with approximately 31 million bp from 6 mussels in each habitat. Using MG-RAST, between 22.5–25.6% were identifiable using the SEED non-redundant database for proteins. Of those fragments that were identifiable through MG-RAST, the composition was dominated by Cyanobacteria and Alpha- and Gamma-proteobacteria. Microbial composition was highly similar between the tidepool and emergent bench mussels, suggesting similar functions across these different microhabitats. One percent of the proteins identified in each sample were related to nitrogen cycling. When normalized to protein discovery rate, the high diversity and abundance of enzymes related to the nitrogen cycle in mussel-associated microbes is as great or greater than that described for other marine metagenomes. In some instances, the nitrogen-utilizing profile of this assemblage was more concordant with soil metagenomes in the Midwestern U.S. than for open ocean system. Carbon fixation and Calvin cycle enzymes further represented 0.65 and 1.26% of all proteins and their abundance was comparable to a number of open ocean marine metagenomes. In sum, the diversity and abundance of nitrogen and carbon cycle related enzymes in the microbes occupying the shells of Mytilus californianus suggest these mussels provide a node for microbial populations and thus biogeochemical processes.
The role of macrobiota in structuring microbial communities along rocky shores
Catherine A Pfister,Jack A Gilbert,Sean M Gibbons
PeerJ , 2015, DOI: 10.7287/peerj.preprints.524v1
Abstract: Rocky shore microbial diversity presents an excellent system to test for microbial habitat specificity or generality, enabling us to decipher how common macrobiota shape microbial community structure. At two coastal locations in the northeast Pacific Ocean, we show that microbial composition was significantly different between inert surfaces, the biogenic surfaces that included rocky shore animals and an alga, and the water column plankton. While all sampled entities had a core of common OTUs, rare OTUs drove differences among biotic and abiotic substrates. For the mussel Mytilus californianus, the shell surface harbored greater alpha diversity compared to internal tissues of the gill and siphon. Strikingly, a 7-year experimental removal of this mussel from tidepools did not significantly alter the microbial community structure of microbes associated with inert surfaces when compared with unmanipulated tidepools. However, bacterial taxa associated with nitrate reduction had greater relative abundance with mussels present, suggesting an impact of increased animal-derived nitrogen on a subset of microbial metabolism. Because the presence of mussels did not affect the structure and diversity of the microbial community on adjacent inert substrates, microbes in this rocky shore environment may be predominantly affected through direct physical association with macrobiota.
The role of macrobiota in structuring microbial communities along rocky shores
Catherine A. Pfister,Jack A. Gilbert,Sean M. Gibbons
PeerJ , 2015, DOI: 10.7717/peerj.631
Abstract: Rocky shore microbial diversity presents an excellent system to test for microbial habitat specificity or generality, enabling us to decipher how common macrobiota shape microbial community structure. At two coastal locations in the northeast Pacific Ocean, we show that microbial composition was significantly different between inert surfaces, the biogenic surfaces that included rocky shore animals and an alga, and the water column plankton. While all sampled entities had a core of common OTUs, rare OTUs drove differences among biotic and abiotic substrates. For the mussel Mytilus californianus, the shell surface harbored greater alpha diversity compared to internal tissues of the gill and siphon. Strikingly, a 7-year experimental removal of this mussel from tidepools did not significantly alter the microbial community structure of microbes associated with inert surfaces when compared with unmanipulated tidepools. However, bacterial taxa associated with nitrate reduction had greater relative abundance with mussels present, suggesting an impact of increased animal-derived nitrogen on a subset of microbial metabolism. Because the presence of mussels did not affect the structure and diversity of the microbial community on adjacent inert substrates, microbes in this rocky shore environment may be predominantly affected through direct physical association with macrobiota.
Rapid Environmental Change over the Past Decade Revealed by Isotopic Analysis of the California Mussel in the Northeast Pacific
Catherine A. Pfister, Sophie J. McCoy, J. Timothy Wootton, Pamela A. Martin, Albert S. Colman, David Archer
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0025766
Abstract: The anthropogenic input of fossil fuel carbon into the atmosphere results in increased carbon dioxide (CO2) into the oceans, a process that lowers seawater pH, decreases alkalinity and can inhibit the production of shell material. Corrosive water has recently been documented in the northeast Pacific, along with a rapid decline in seawater pH over the past decade. A lack of instrumentation prior to the 1990s means that we have no indication whether these carbon cycle changes have precedence or are a response to recent anthropogenic CO2 inputs. We analyzed stable carbon and oxygen isotopes (δ13C, δ18O) of decade-old California mussel shells (Mytilus californianus) in the context of an instrumental seawater record of the same length. We further compared modern shells to shells from 1000 to 1340 years BP and from the 1960s to the present and show declines in the δ13C of modern shells that have no historical precedent. Our finding of decline in another shelled mollusk (limpet) and our extensive environmental data show that these δ13C declines are unexplained by changes to the coastal food web, upwelling regime, or local circulation. Our observed decline in shell δ13C parallels other signs of rapid changes to the nearshore carbon cycle in the Pacific, including a decline in pH that is an order of magnitude greater than predicted by an equilibrium response to rising atmospheric CO2, the presence of low pH water throughout the region, and a record of a similarly steep decline in δ13C in algae in the Gulf of Alaska. These unprecedented changes and the lack of a clear causal variable underscores the need for better quantifying carbon dynamics in nearshore environments.
Influence of the topography of the surface of the Earth on vertical sounding of the temperature profile
A. Pfister,H. Fischer
Annales Geophysicae (ANGEO) , 2003,
Abstract: Atmospheric temperature and humidity fields as well as information on other meteorological parameters are nowadays retrieved from radiance measurements recorded by operational meteorological satellites. Up to now, the inversion procedures used only take into account crude information on the topography of the Earth's surface. However, the applied radiative transfer codes have to consider the Earth's surface as the lower boundary of the atmospheric model and, therefore, need a more precise mean elevation and a classification of the roughness of the Earth's surface. The influence of the topography of the Earth surface on retrieved temperature profiles is studied by using a physico-statistical inversion method. An objective analysis is made of the more precise mean elevation and derivation of roughness parameters using a new high-resolution digital elevation model (DEM) with a resolution of 500 m×500 m. By means of a geomorphological process and a newly developed topography rejection test, areas with a high surface roughness are localized and singled out. The influence of topography on the retrieved temperature profiles is illustrated by case studies. Changes are found predominantly in areas with a high variation of topography. Using the new high-resolution DEM and the topography rejection test, the geographical position of the calculated temperature profiles tends to be shifted towards areas with a small vertical variation of topography. The mean elevation determined by the new elevation model better characterizes the area observed. Hence, the temperature profiles can be calculated down to lower atmospheric levels. Furthermore, a guess profile better describing the atmospheric situation is selected by the more precise elevation. In addition, the temperature profiles obtained near the coast are improved considerably by the more precise determination of the surface property `sea' and `land,' respectively. Integration of an independent physical information such as topography leads, on average, to a slight improvement of the results of the physico-statistical inversion procedure. In some cases, however, significant improvements have been achieved regarding the desired accuracy of temperature profiles of the order of 1 K. In future, the spatial resolution of new high-resolution sounding instrumentation on the next generation of operational meteorological satellites will be increased. To exploit the resolving power of this new instrumentation, the different variation of the topography of the Earth surface, especially in regions with a high variation of topograph
Exponential Estimates in Adiabatic Quantum Evolution
A. Joye,C. -E. Pfister
Physics , 1998,
Abstract: We review recent results concerning the exponential behaviour of transition probabilities across a gap in the adiabatic limit of the time-dependent Schr\"odinger equation. They range from an exponential estimate in quite general situations to asymptotic Landau-Zener type formulae for finite dimensional systems, or systems reducible to this case.
Wardrobe Malfunctions and the Measurement of Internet Behaviour  [PDF]
Roland Pfister
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.23042
Abstract: The wardrobe malfunction – an unanticipated exposure of bodily parts in the public – has become a prevailing issue in concerts, shows and other celebrity events that is reliably reported by the media. The internet as the fastest source for celebrity gossip allows measuring the impact of such wardrobe malfunctions on the public in-terest in a celebrity. This measurement in turn allows conclusions about intention, motivation, and internet be-haviour of a wide variety of internet users. The present study exemplifies the use of an innovative non-reactive measure of active interest – the Search Volume Index – to assess the impact of a variety of internet-related phe-nomena, including wardrobe malfunctions. Results indicate that interest in a celebrity increases immediately af-ter such an event and stays at a high level for about three weeks (the wardrobe plateau). This special form of ce-lebrity gossip thus meets a constant interest of a substantial proportion of internet users.
Palliative radikale (Zysto-) Prostatektomie bei lokal fortgeschrittenem kastrationsresistentem Prostatakarzinom (KRPCA)
Pfister D,van Erps T,Heidenreich A
Journal für Urologie und Urogyn?kologie , 2011,
Abstract: Trotz prim rer lokaler Radiatio und Systemtherapie kann das lokal fortgeschrittene kastrationsresistente Prostatakarzinom (KRPCA) bei weiterer Progression zu lokalen Symptomen durch Rektum- und Blasenhalsinfiltration führen. Wir berichten über unsere Erfahrungen palliativer radikalchirurgischer Therapiekonzepte. Bei 20 Patienten wurde zwischen 2004 und 2010 aufgrund lokaler Symptome bei lokal fortgeschrittenem Prostatakarzinom eine palliative radikale Chirurgie durchgeführt. Im Vordergrund stand eine ausgepr gte Schmerzsymptomatik bei zwei Drittel der Patienten, gefolgt von subvesikaler Obstruktion, rezidivierenden interventionspflichtigen Makroh maturien und chronischem Subileus bei Rektumbeteiligung. 18 der Patienten waren kastrationsresistent nach den g ngigen Leitlinien. Als operative Ma nahmen wurde eine Zystoprostatektomie bei 15 Patienten, davon 3 mit zus tzlicher Rektumresektion, und bei 4 Patienten eine radikale Prostatektomie durchgeführt. Ein Patient erhielt bei schlechter Prognose eine beidseitige Ureterhautfistel und eine Kolostomie. Der mittlere station re Aufenthalt lag bei 14 (10 23) Tagen. Es gab keine signifikanten intraoperativen Komplikationen. Postoperativ kam es zu 3 interventionspflichtigen Komplikationen: einem intrapelvinen Abszess, einer symptomatischen Lymphozele sowie einer ableitungsbedürftigen Pyonephrose. Eine Reduktion von Symptomen konnte in 80 % der F lle erreicht werden. Das mittlere symptomfreie Intervall lag bei 15,3 (6 25) Monaten, das mittlere überleben bei 20,3 (9 28) Monaten. Die radikale palliative Tumorchirurgie kann zu einer dauerhaften Symptomreduktion führen und sollte als individuelles Therapiekonzept bei einem ausgew hlten Patientengut Anwendung finden.
STDP in Oscillatory Recurrent Networks: Theoretical Conditions for Desynchronization and Applications to Deep Brain Stimulation
Jean-Pascal Pfister,Peter A. Tass
Frontiers in Computational Neuroscience , 2010, DOI: 10.3389/fncom.2010.00022
Abstract: Highly synchronized neural networks can be the source of various pathologies such as Parkinson’s disease or essential tremor. Therefore, it is crucial to better understand the dynamics of such networks and the conditions under which a high level of synchronization can be observed. One of the key factors that influences the level of synchronization is the type of learning rule that governs synaptic plasticity. Most of the existing work on synchronization in recurrent networks with synaptic plasticity are based on numerical simulations and there is a clear lack of a theoretical framework for studying the effects of various synaptic plasticity rules. In this paper we derive analytically the conditions for spike-timing dependent plasticity (STDP) to lead a network into a synchronized or a desynchronized state. We also show that under appropriate conditions bistability occurs in recurrent networks governed by STDP. Indeed, a pathological regime with strong connections and therefore strong synchronized activity, as well as a physiological regime with weaker connections and lower levels of synchronization are found to coexist. Furthermore, we show that with appropriate stimulation, the network dynamics can be pushed to the low synchronization stable state. This type of therapeutical stimulation is very different from the existing high-frequency stimulation for deep brain stimulation since once the stimulation is stopped the network stays in the low synchronization regime.
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