58 research outputs found
ATP Antagonizes Thrombin-Induced Signal Transduction through 12(S)-HETE and cAMP
In this study we have investigated the role of extracellular ATP on thrombin induced-platelet aggregation (TIPA) in washed
human platelets. ATP inhibited TIPA in a dose-dependent manner and this inhibition was abolished by apyrase but not by
adenosine deaminase (ADA) and it was reversed by extracellular magnesium. Antagonists of P2Y1 and P2Y12 receptors had
no effect on this inhibition suggesting that a P2X receptor controlled ATP-mediated TIPA inhibition. ATP also blocked
inositol phosphates (IP1, IP2, IP3) generation and [Ca2+]i mobilization induced by thrombin. Thrombin reduced cAMP levels
which were restored in the presence of ATP. SQ-22536, an adenylate cyclase (AC) inhibitor, partially reduced the inhibition exerted by ATP on TIPA. 12-lipoxygenase (12-LO) inhibitors, nordihidroguaretic acid (NDGA) and 15(S)-hydroxy-5,8,11,13- eicosatetraenoic acid (15(S)-HETE), strongly prevented ATP-mediated TIPA inhibition. Additionally, ATP inhibited the increase of 12(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12(S)-HETE) induced by thrombin. Pretreatment with both SQ- 22536 and NDGA almost completely abolished ATP-mediated TIPA inhibition. Our results describe for the first time that ATP implicates both AC and 12-LO pathways in the inhibition of human platelets aggregation in response to agonists.Fil: Burzaco, Jaione. UNIVERSIDAD DEL PAIS VASCO;Fil: Conde, Manuel. UNIVERSIDAD DEL PAIS VASCO;Fil: Parada, Luis Antonio. Consejo Nacional de Invest.cientif.y Tecnicas. Centro Cientifico Tecnol.conicet - Salta. Instituto de Patologia Experimental;Fil: Zugaza, José L.. UNIVERSIDAD DEL PAIS VASCO;Fil: Dehaye, Jean-Paul. UNIVERSIDAD DEL PAIS VASCO;Fil: Marino, Aída. UNIVERSIDAD DEL PAIS VASCO
Improving the Representation and Conversion of Mathematical Formulae by Considering their Textual Context
Mathematical formulae represent complex semantic information in a concise
form. Especially in Science, Technology, Engineering, and Mathematics,
mathematical formulae are crucial to communicate information, e.g., in
scientific papers, and to perform computations using computer algebra systems.
Enabling computers to access the information encoded in mathematical formulae
requires machine-readable formats that can represent both the presentation and
content, i.e., the semantics, of formulae. Exchanging such information between
systems additionally requires conversion methods for mathematical
representation formats. We analyze how the semantic enrichment of formulae
improves the format conversion process and show that considering the textual
context of formulae reduces the error rate of such conversions. Our main
contributions are: (1) providing an openly available benchmark dataset for the
mathematical format conversion task consisting of a newly created test
collection, an extensive, manually curated gold standard and task-specific
evaluation metrics; (2) performing a quantitative evaluation of
state-of-the-art tools for mathematical format conversions; (3) presenting a
new approach that considers the textual context of formulae to reduce the error
rate for mathematical format conversions. Our benchmark dataset facilitates
future research on mathematical format conversions as well as research on many
problems in mathematical information retrieval. Because we annotated and linked
all components of formulae, e.g., identifiers, operators and other entities, to
Wikidata entries, the gold standard can, for instance, be used to train methods
for formula concept discovery and recognition. Such methods can then be applied
to improve mathematical information retrieval systems, e.g., for semantic
formula search, recommendation of mathematical content, or detection of
mathematical plagiarism.Comment: 10 pages, 4 figure
Renormalization : A number theoretical model
We analyse the Dirichlet convolution ring of arithmetic number theoretic
functions. It turns out to fail to be a Hopf algebra on the diagonal, due to
the lack of complete multiplicativity of the product and coproduct. A related
Hopf algebra can be established, which however overcounts the diagonal. We
argue that the mechanism of renormalization in quantum field theory is modelled
after the same principle. Singularities hence arise as a (now continuously
indexed) overcounting on the diagonals. Renormalization is given by the map
from the auxiliary Hopf algebra to the weaker multiplicative structure, called
Hopf gebra, rescaling the diagonals.Comment: 15 pages, extended version of talks delivered at SLC55 Bertinoro,Sep
2005, and the Bob Delbourgo QFT Fest in Hobart, Dec 200
Put to the Test: For a New Sociology of Testing
In an age defined by computational innovation, testing seems to have become ubiquitous, and tests are routinely deployed as a form of governance, a marketing device, an instrument for political intervention, and an everyday practice to evaluate the self. This essay argues that something more radical is happening here than simply attempts to move tests from the laboratory into social settings. The challenge that a new sociology of testing must address is that ubiquitous testing changes the relations between science, engineering and sociology: Engineering is today in the very stuff of where society happens. It is not that the tests of 21st Century engineering occur within a social context but that it is the very fabric of the social that is being put to the test. To understand how testing and the social relate today, we must investigate how testing operates on social life, through the modification of its settings. One way to clarify the difference is to say that the new forms of testing can be captured neither within the logic of the field test nor of the controlled experiment. Whereas tests once happened inside social environments, today’s tests directly and deliberately modify the social environment
Studies on polyethylene pellets modified by low dose radiation prior to part formation
When it is combined with other processing steps, radiation modification of polyethylene pellets prior to conversion into end products (formed parts) has brought about significant improvement of various properties of the polymers and products made from them despite the low cross-linking degree. The physical and chemical changes of the polymers after the radiation modification by electron beam (EB) and gamma ray at low dose levels are studied using various characterizations. Fourier Transform Infrared Spectroscopy (FTIR) showed the formation of carbonyl groups and changes of unsaturated bonds. Gel permeation chromatography (GPC) results indicated broadening of the molecular weight distribution. Rheological analysis in linear visco-elasticity regime showed increased dynamic viscosity and large amplitude oscillatory shear (LAOS) analysis showed increased hysteresis. It is proposed that the radiation at low dose levels and under ambient conditions induces various reactions on the polymer chains including long chain branching, oxidation and changes of unsaturated bonds. (c) 2005 Elsevier B.V. All rights reserved
- …