2,419 research outputs found
Massive scalar fields in the early Universe
We discuss the role of gravitational excitons/radions in different
cosmological scenarios. Gravitational excitons are massive moduli fields which
describe conformal excitations of the internal spaces and which, due to their
Planck-scale suppressed coupling to matter fields, are WIMPs. It is
demonstrated that, depending on the concrete scenario, observational
cosmological data set strong restrictions on the allowed masses and initial
oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on
Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003),
Olinda-PE, Brazi
Multidimensional perfect fluid cosmology with stable compactified internal dimensions
Multidimensional cosmological models in the presence of a bare cosmological
constant and a perfect fluid are investigated under dimensional reduction to
4-dimensional effective models. Stable compactification of the internal spaces
is achieved for a special class of perfect fluids. The external space behaves
in accordance with the standard Friedmann model. Necessary restrictions on the
parameters of the models are found to ensure dynamical behavior of the external
(our) universe in agreement with observations.Comment: 11 pages, Latex2e, uses IOP packages, submitted to Class.Quant.Gra
Quasiparticle Corrections to the Electronic Properties of Anion Vacancies at GaAs(110) and InP(110)
We propose a new method for calculating optical defect levels and
thermodynamic charge-transition levels of point defects in semiconductors,
which includes quasiparticle corrections to the Kohn-Sham eigenvalues of
density-functional theory. Its applicability is demonstrated for anion
vacancies at the (110) surfaces of III-V semiconductors. We find the (+/0)
charge-transition level to be 0.49 eV above the surface valence-band maximum
for GaAs(110) and 0.82 eV for InP(110). The results show a clear improvement
over the local-density approximation and agree closely with an experimental
analysis.Comment: 4 pages including 1 figure, RevTe
MetaboLab - advanced NMR data processing and analysis for metabolomics
Background\ud
Despite wide-spread use of Nuclear Magnetic Resonance (NMR) in metabolomics for the analysis of biological samples there is a lack of graphically driven, publicly available software to process large one and two-dimensional NMR data sets for statistical analysis.\ud
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Results\ud
Here we present MetaboLab, a MATLAB based software package that facilitates NMR data processing by providing automated algorithms for processing series of spectra in a reproducible fashion. A graphical user interface provides easy access to all steps of data processing via a script builder to generate MATLAB scripts, providing an option to alter code manually. The analysis of two-dimensional spectra (1H,13C-HSQC spectra) is facilitated by the use of a spectral library derived from publicly available databases which can be extended readily. The software allows to display specific metabolites in small regions of interest where signals can be picked. To facilitate the analysis of series of two-dimensional spectra, different spectra can be overlaid and assignments can be transferred between spectra. The software includes mechanisms to account for overlapping signals by highlighting neighboring and ambiguous assignments.\ud
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Conclusions\ud
The MetaboLab software is an integrated software package for NMR data processing and analysis, closely linked to the previously developed NMRLab software. It includes tools for batch processing and gives access to a wealth of algorithms available in the MATLAB framework. Algorithms within MetaboLab help to optimize the flow of metabolomics data preparation for statistical analysis. The combination of an intuitive graphical user interface along with advanced data processing algorithms facilitates the use of MetaboLab in a broader metabolomics context.\ud
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Stabilization of internal spaces in multidimensional cosmology
Effective 4-dimensional theories are investigated which were obtained under
dimensional reduction of multidimensional cosmological models with a minimal
coupled scalar field as matter source. Conditions for the internal space
stabilization are considered and the possibility for inflation in the external
space is discussed. The electroweak as well as the Planck fundamental scale
approaches are investigated and compared with each other. It is shown that
there exists a rescaling for the effective cosmological constant as well as for
gravitational exciton masses in the different approaches.Comment: 12 pages, LaTeX2e, to appear in Phys.Rev.D, note adde
Equation of State of Oscillating Brans-Dicke Scalar and Extra Dimensions
We consider a Brans-Dicke scalar field stabilized by a general power law
potential with power index at a finite equilibrium value. Redshifting
matter induces oscillations of the scalar field around its equilibrium due to
the scalar field coupling to the trace of the energy momentum tensor. If the
stabilizing potential is sufficiently steep these high frequency oscillations
are consistent with observational and experimental constraints for arbitrary
value of the Brans-Dicke parameter . We study analytically and
numerically the equation of state of these high frequency oscillations in terms
of the parameters and and find the corresponding evolution of the
universe scale factor. We find that the equation of state parameter can be
negative and less than -1 but it is not related to the evolution of the scale
factor in the usual way. Nevertheless, accelerating expansion is found for a
certain parameter range. Our analysis applies also to oscillations of the size
of extra dimensions (the radion field) around an equilibrium value. This
duality between self-coupled Brans-Dicke and radion dynamics is applicable for
where D is the number of extra dimensions.Comment: 10 two-column pages, RevTex4, 8 figures. Added clarifying
discussions, new references. Accepted in Phys. Rev. D (to appear
Entanglement Efficiencies in PT-Symmetric Quantum Mechanics
The degree of entanglement is determined for an arbitrary state of a broad
class of PT-symmetric bipartite composite systems. Subsequently we quantify the
rate with which entangled states are generated and show that this rate can be
characterized by a small set of parameters. These relations allow one in
principle to improve the ability of these systems to entangle states. It is
also noticed that many relations resemble corresponding ones in conventional
quantum mechanics.Comment: Published version with improved figures, 5 pages, 2 figure
Enhanced product functionality with life cycle units
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Cycle economy is not only ecologically reasonable but also a chance for new business. Selling utilization instead of selling products is advantageous once additional costs for information processing and logistics are less than costs for underutilized capacity. A competitive provider offers product functionality in quality, time and location as required by the user. Lifetime component monitoring is conditional for this performance. Modern microelectronic technology enables the acquisition of component deterioration with sensorial devices, information processing and storing with microcontrollers and initiating appropriate actions such as maintenance. The architecture of a microsystem called the life cycle unit (LCU) for product and component monitoring is introduced and specified. Product examples illustrate some application areas.DFG, SFB 281, Demontagefabriken zur Rückgewinnung von Ressourcen in Produkt- und Materialkreisläufe
Bouncing inflation in nonlinear gravitational model
We study a gravitational model with curvature-squared and
curvature-quartic nonlinearities. The effective scalar degree of freedom
(scalaron) has a multi-valued potential consisting of a number
of branches. These branches are fitted with each other in the branching and
monotonic points. In the case of four-dimensional space-time, we show that the
monotonic points are penetrable for scalaron while in the vicinity of the
branching points scalaron has the bouncing behavior and cannot cross these
points. Moreover, there are branching points where scalaron bounces an infinite
number of times with decreasing amplitude and the Universe asymptotically
approaches the de Sitter stage. Such accelerating behavior we call bouncing
inflation. For this accelerating expansion there is no need for original
potential to have a minimum or to check the slow-roll conditions. A
necessary condition for such inflation is the existence of the branching
points. This is a new type of inflation. We show that bouncing inflation takes
place both in the Einstein and Brans-Dicke frames.Comment: RevTex 13 pages, 13 figures, a few comments and references adde
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