7,634 research outputs found
Simultaneous Kummer congruences and -orientations of KO and tmf
Building on results of M. Ando, M.J. Hopkins and C. Rezk, we show the
existence of uncountably many -String orientations of real
K-theory KO and of topological modular forms tmf, generalizing the -
(resp. the Witten) genus. Furthermore, the obstruction to lifting an
-String orientations from KO to tmf is identified with a
classical Iwasawa-theoretic condition. The common key to all these results is a
precise understanding of the classical Kummer congruences, imposed for all
primes simultaneously. This result is of independent arithmetic interest.Comment: final versio
Reconstruction methods for acoustic particle detection in the deep sea using clusters of hydrophones
This article focuses on techniques for acoustic noise reduction, signal
filters and source reconstruction. For noise reduction, bandpass filters and
cross correlations are found to be efficient and fast ways to improve the
signal to noise ratio and identify a possible neutrino-induced acoustic signal.
The reconstruction of the position of an acoustic point source in the sea is
performed by using small-volume clusters of hydrophones (about 1 cubic meter)
for direction reconstruction by a beamforming algorithm. The directional
information from a number of such clusters allows for position reconstruction.
The algorithms for data filtering, direction and position reconstruction are
explained and demonstrated using simulated data.Comment: 7 pages, 13 figure
Contribution of the nucleon-hyperon reaction channels to K production in proton-nucleus collisions
The cross sections for producing K mesons in nucleon-hyperon elementary
processes are estimated assuming one-pion exchange and using the experimentally
known pion-hyperon cross sections. The results are implemented in a transport
model which is applied to calculation of proton-nucleus collisions. In
significant difference to earlier estimates for heavy-ion collisions the
inclusion of the nucleon-hyperon cross section roughly doubles the K
production in near-threshold proton-nucleus collisions
Integration of Acoustic Neutrino Detection Methods into ANTARES
The ANTARES Neutrino Telescope is a water Cherenkov detector currently under
construction in the Mediterranean Sea. It is also designed to serve as a
platform for investigations of the deep-sea environment. In this context, the
ANTARES group at the University of Erlangen will integrate acoustic sensors
within the infrastructure of the experiment. With this dedicated setup, tests
of acoustic particle detection methods and deep-sea acoustic background studies
shall be performed. The aim of this project is to evaluate the feasibility of a
future acoustic neutrino telescope in the deep sea operating in the ultra-high
energy regime. In these proceedings, the implementation of the project is
described in the context of the premises and challenges set by the physics of
acoustic particle detection and the integration into an existing
infrastructure.Comment: 6 pages, 5 figures, to appear in the proceedings of the International
ARENA Workshop, May 28-30th, 2006, University of Northumbri
Measurement of pH. Definition, Standards, and Procedures
The definition of a “primary method of measurement” [1] has permitted
a full consideration of the definition of primary standards for pH, determined by a
primary method (cell without transference, Harned cell), of the definition of secondary
standards by secondary methods, and of the question whether pH, as a conventional
quantity, can be incorporated within the internationally accepted system
of measurement, the International System of Units (SI, Système International
d’Unités). This approach has enabled resolution of the previous compromise
IUPAC 1985 Recommendations [2]. Furthermore, incorporation of the uncertainties
for the primary method, and for all subsequent measurements, permits the
uncertainties for all procedures to be linked to the primary standards by an unbroken
chain of comparisons. Thus, a rational choice can be made by the analyst of
the appropriate procedure to achieve the target uncertainty of sample pH.
Accordingly, this document explains IUPAC recommended definitions, procedures,
and terminology relating to pH measurements in dilute aqueous solutions in
the temperature range 5–50 °C. Details are given of the primary and secondary
methods for measuring pH and the rationale for the assignment of pH values with
appropriate uncertainties to selected primary and secondary substances
Identification of novel Cyclooxygenase-2-dependent genes in Helicobacter pylori infection in vivo
<p>Abstract</p> <p>Background</p> <p><it>Helicobacter pylori </it>is a crucial determining factor in the pathogenesis of benign and neoplastic gastric diseases. Cyclooxygenase-2 (Cox-2) is the inducible key enzyme of arachidonic acid metabolism and is a central mediator in inflammation and cancer. Expression of the <it>Cox-2 </it>gene is up-regulated in the gastric mucosa during <it>H. pylori </it>infection but the pathobiological consequences of this enhanced Cox-2 expression are not yet characterized. The aim of this study was to identify novel genes down-stream of Cox-2 in an <it>in vivo </it>model, thereby identifying potential targets for the study of the role of Cox- 2 in <it>H. pylori </it>pathogenesis and the initiation of pre- cancerous changes.</p> <p>Results</p> <p>Gene expression profiles in the gastric mucosa of mice treated with a specific Cox-2 inhibitor (NS398) or vehicle were analysed at different time points (6, 13 and 19 wk) after <it>H. pylori </it>infection. <it>H. pylori </it>infection affected the expression of 385 genes over the experimental period, including regulators of gastric physiology, proliferation, apoptosis and mucosal defence. Under conditions of Cox-2 inhibition, 160 target genes were regulated as a result of <it>H. pylori </it>infection. The Cox-2 dependent subset included those influencing gastric physiology (<it>Gastrin, Galr1</it>), epithelial barrier function (<it>Tjp1, connexin45, Aqp5</it>), inflammation (<it>Icam1</it>), apoptosis (<it>Clu</it>) and proliferation (<it>Gdf3, Igf2</it>). Treatment with NS398 alone caused differential expression of 140 genes, 97 of which were unique, indicating that these genes are regulated under conditions of basal Cox-2 expression.</p> <p>Conclusion</p> <p>This study has identified a panel of novel Cox-2 dependent genes influenced under both normal and the inflammatory conditions induced by <it>H. pylori </it>infection. These data provide important new links between Cox-2 and inflammatory processes, epithelial repair and integrity.</p
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