2,200 research outputs found
Preliminary results of the MIDTAL project: a microarray chip to monitor toxic dinoflagellates in the Orkney Islands, U.K.
Harmful algae can cause economic damage to fisheries and tourism. Additionally, toxins produced by harmful algae and ingested via contaminated shellfish can be potentially fatal to humans. Monitoring these harmful algae can be difficult as determining cell morphology by light microscopy may be insufficient to give definitive species attribution. The goal of the EU FP7 project MIDTAL (microarrays for the detection of toxic algae) was to achieve rapid species identification using species specific probes for rRNA genes in a microarray chip format. Field samples from the Orkney Islands, an area of the U.K. that has a number of nuisance and toxic species were tested with the second generation of the microarray chip. Species specific probes were looked at for the toxin producing dinoflagellates Alexandrium tamarense Group III (North American clade) and Dinophysis acuta and also general class probes for Dinophyta, Heterokontaphyta and Prymnesiophyta over the course of a year. These were compared with light microscopy cell counts. A good agreement in determining presence and absence between the methods was found. The second generation microarray is potentially more sensitive than cell counts. However, further work is needed to ensure that the microarray signal for each species provides an accurate quantitative assessment
Substructure in clusters containing wide-angle tailed radio galaxies. I. New redshifts
We present new redshifts and positions for 635 galaxies in nine rich clusters
containing Wide-Angle Tailed (WAT) radio galaxies. Combined with existing data,
we now have a sample of 18 WAT-containing clusters with more than 10 redshifts.
This sample contains a substantial portion of the WAT clusters in the VLA 20 cm
survey of Abell clusters, including 75% of WAT clusters in the complete survey
(z0.09. It is a representative sample
which should not contain biases other than selection by radio morphology. We
graphically present the new data using histograms and sky maps. A
semi-automated procedure is used to search for emission lines in the spectra in
order to add and verify galaxy redshifts. We find that the average apparent
fraction of emission line galaxies is about 9% in both the clusters and the
field. We investigate the magnitude completeness of our redshift surveys with
CCD data for a test case, Abell 690. This case indicates that our galaxy target
lists are deeper than the detection limit of a typical MX exposure, and they
are 82% complete down to R=19.0. The importance of the uniformity of the
placement of fibers on targets is posited, and we evaluate this in our
datasets. We find some cases of non-uniformities which may influence dynamical
analyses. A second paper will use this database to look for correlations
between the WAT radio morphology and the cluster's dynamical state.Comment: 15 pages, 5 figures, 7 tables. To appear in the Astronomical Journa
Global wellposedness for a certain class of large initial data for the 3D Navier-Stokes Equations
In this article, we consider a special class of initial data to the 3D
Navier-Stokes equations on the torus, in which there is a certain degree of
orthogonality in the components of the initial data. We showed that, under such
conditions, the Navier-Stokes equations are globally wellposed. We also showed
that there exists large initial data, in the sense of the critical norm
that satisfies the conditions that we considered.Comment: 13 pages, updated references for v
Stochastic Processes in Yellow and Red Pulsating Variables
Random changes in pulsation period are well established in cool pulsating
stars, in particular the red giant variables: Miras, semi-regulars of types A
and B, and RV Tau variables. Such effects are also observed in a handful of
Cepheids, the SX Phe variable XX Cyg, and, most recently, the red supergiant
variable, BC Cyg, a type C semi-regular. The nature of such fluctuations is
seemingly random over a few pulsation cycles of the stars, yet the regularity
of the primary pulsation mechanism dominates over the long term. The degree of
stochasticity is linked to the dimensions of the stars, the randomness
parameter 'e' appearing to correlate closely with mean stellar radius through
the period 'P', with an average value of e/P = 0.0136+-0.0005. The physical
processes responsible for such fluctuations are uncertain, but presumably
originate in temporal modifications of envelope convection in such stars.Comment: Poster given at the "Stellar Pulsation: Challenges for Theory and
Observation" conference in Santa Fe, New Mexico (2009
Thin layers and camouflage: hidden \u3cem\u3ePseudo-nitzschia\u3c/em\u3e spp. (Bacillariophyceae) populations in a fjord in the San Juan Islands, Washington, USA
Two sets of observations were made on the distribution of Pseudo-nitzschia taxa in a fjord in the San Juan Islands, Washington, USA. From May 21 to 31, 1996, we observed the spatio-temporal distribution of a dense bloom of P. fraudulenta. Microscopic observations of live material were compared to physical-optical water-column structure, currents and wind. At the start of the study, dense concentrations of Pseudo-nitzschia spp. were observed directly at the surface. Optical profiles indicated that most cells were concentrated in a thin layer at ~5 m depth, which appeared to be contiguous throughout the sound. Several days later, sustained winds forced a plume of lighter water over the surface of the sound, displacing the original water mass, with its entrained flora, to depth. The resulting near-bottom thin layer persisted for several days, and contained \u3e106 Pseudo-nitzschia spp. cells l-1. Microscopic examination of live cells from the deep layer revealed that colonies were alive and motile. In 1996 and again in 1998, we observed P. pseudodelicatissima living within colonies of Chaetoceros socialis. Water-column thin layers, near-bottom thin layers and populations of Pseudo-nitzschia spp. within C. socialis colonies could easily escape detection by routine monitoring procedures, and may be a potential source of unexplained toxicity events
A common polymorphism in the oxygen-dependent degradation (ODD) domain of hypoxia inducible factor-1α (HIF-1α) does not impair Pro-564 hydroxylation
BACKGROUND: The hypoxia-inducible factor (HIF) transcription complex, which is activated by low oxygen tension, controls a diverse range of cellular processes including angiogenesis and erythropoiesis. Under normoxic conditions, the α subunit of HIF is rapidly degraded in a manner dependent on hydroxylation of two conserved proline residues at positions 402 and 564 in HIF-1α in the oxygen-dependent degradation (ODD) domain. This allows subsequent recognition by the von Hippel-Lindau (VHL) tumor suppressor protein, which targets HIF for degradation by the ubiquitin-proteasome pathway. Under hypoxic conditions, prolyl hydroxylation of HIF is inhibited, allowing it to escape VHL-mediated degradation. The transcriptional regulation of the erythropoietin gene by HIF raises the possibility that HIF may play a role in disorders of erythropoiesis, such as idiopathic erythrocytosis (IE). RESULTS: Patients with IE were screened for changes in the HIF-1α coding sequence, and a change in the ODD domain that converts Pro-582 to Ser was identified in several patients. This same change, however, was also detected at a significant frequency, 0.073, in unaffected controls compared to 0.109 in the IE patient group. In vitro hydroxylation assays examining this amino acid change failed to reveal a discernible effect on HIF hydroxylation at Pro-564. CONCLUSION: The Pro582Ser change represents a common polymorphism of HIF-1α that does not impair HIF-1α prolyl hydroxylation. Although the Pro582Ser polymorphism is located in the ODD domain of HIF-1α it does not diminish the association of HIF-1α with VHL. Thus, it is unlikely that this polymorphism accounts for the erythrocytosis in the group of IE patients studied
What is the initiation step of the Grubbs-Hoveyda olefin metathesis catalyst?
Density function theory calculations reveal that the Grubbs-Hoveyda olefin metathesis pre-catalyst is activated by the formation of a complex in which the incoming alkene substrate and outgoing alkoxy ligand are both clearly associated with the ruthenium centre. The computed energies for reaction are in good agreement with the experimental values, reported here
Reproduced, reinterpreted, lost: Trajectories of scientific knowledge across contexts
This article reports on a research project that uses two innovative heuristics to examine the changes that texts – produced to disseminate new scientific knowledge – undergo when they travel across space and time. A critical analysis of such transformations would enhance our understanding of the processes involved in knowledge dissemination and inform the practice of communicating scientific knowledge to a variety of audiences. Based on our study of 520 closely linked science and science-related sources collected over 12 months in 2016, we argue that when scientific knowledge is re-contextualized to be disseminated to different audiences, it is not simply rephrased or simplified to make it more accessible. Rather, it also undergoes transformational processes that involve issues of social power, authority and access that require new analytical tools to surface more clearly. We report on the methodology of the study with a particular focus on its heuristics, and the transformations that result from a critical analysis of the data collected. We finally discuss a number of theoretical and practical implications in relation to contemporary practices for re-entextualizing scientific knowledge
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