2,543 research outputs found
European air quality maps 2005 including uncertainty analysis
The objective of this report is (a) the updating and refinement of European air quality maps based on annual statistics of the 2005 observational data reported by EEA Member countries in 2006, and (b) the further improvement of the interpolation methodologies. The paper presents the results achieved and an uncertainty analysis of the interpolated maps and builds upon earlier reports from Horalék et al. (2005; 2007)
Classification of Higher Dimensional Spacetimes
We algebraically classify some higher dimensional spacetimes, including a
number of vacuum solutions of the Einstein field equations which can represent
higher dimensional black holes. We discuss some consequences of this work.Comment: 16 pages, 1 Tabl
WZW-like Action for Heterotic String Field Theory
We complete the construction of the Neveu-Schwarz sector of heterotic string
field theory begun in hep-th/0406212 by giving a closed-form expression for the
action and gauge transformations. Just as the Wess-Zumino-Witten (WZW) action
for open superstring field theory can be constructed from pure-gauge fields in
bosonic open string field theory, our heterotic string field theory action is
constructed from pure-gauge fields in bosonic closed string field theory. The
construction involves a simple alternative form of the WZW action which is
consistent with the algebraic structures of closed string field theory.Comment: 22 pages, no figures, LaTeX2
Organic layers on silicon result in a unique hybrid fet
A Field-Effect Transistor (FET) is presented that combines the conventional lay-out of the silicon substrate (channel and source and drain connections) with a Si-C linked organic gate insulator contacted via an organic, conducting polymer. It is shown that this hybrid device combines the excellent electrical behavior of the silicon substrate and the ease of use and good properties of organic insulators and contacting materials.\ud
Keywords: organic monolayer, FET, conducting polyme
Îł-H2AX foci as in vivo effect biomarker in children emphasize the importance to minimize x-ray doses in paediatric CT imaging
Objectives: Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting.
Methods: From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring gamma-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models.
Results: Despite the low CT doses, a median increase of 0.13 gamma-H2AX foci/cell was observed. Plotting the induced gamma-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13% respectively.
Conclusion: CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols
Design and fabrication of a low cost implantable bladder pressure monitor
In the frame of the Flemish Community funded project Bioflex we developed and fabricated an implant for short term (< 7 days) bladder pressure monitoring, and diagnosis of incontinence. This implant is soft and flexible to prevent damaging the bladder's inner wall. It contains a standard flexible electronic circuit connected to a battery, which are embedded in surface treated silicone to enhance the biocompatibility and prevent salt deposition. This article describes the fabrication of the pill and the results of preliminary cytotoxicity tests. The electronic design and its tests, implantation and the result of the in-vivo experimentation will be presented in other articles
A perturbative analysis of tachyon condensation
Tachyon condensation in the open bosonic string is analyzed using a
perturbative expansion of the tachyon potential around the unstable D25-brane
vacuum. Using the leading terms in the tachyon potential, Pad\'e approximants
can apparently give the energy of the stable vacuum to arbitrarily good
accuracy. Level-truncation approximations up to level 10 for the coefficients
in the tachyon potential are extrapolated to higher levels and used to find
approximants for the full potential. At level 14 and above, the resulting
approximants give an energy less than -1 in units of the D25-brane tension, in
agreement with recent level-truncation results by Gaiotto and Rastelli. The
extrapolated energy continues to decrease below -1 until reaching a minimum
near level 26, after which the energy turns around and begins to approach -1
from below. Within the accuracy of this method, these results are completely
consistent with an energy which approaches -1 as the level of truncation is
taken to be arbitrarily large.Comment: 8 pages, 3 eps figures, Latex; v2: typo correcte
Layer charge instability in unbalanced bilayer systems in the quantum Hall regime
Measurements in GaAs hole bilayers with unequal layer densities reveal a
pronounced magneto-resistance hysteresis at the magnetic field positions where
either the majority or minority layer is at Landau level filling factor one. At
a fixed field in the hysteretic regions, the resistance exhibits an unusual
time dependence, consisting of random, bidirectional jumps followed by slow
relaxations. These anomalies are apparently caused by instabilities in the
charge distribution of the two layers.Comment: 4 pages, 4 figure
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