Gravitational radiation from elastic particle scattering in models with extra dimensions

In this paper we derive a formula for the energy loss due to elastic N to N particle scattering in models with extra dimensions that are compactified on a radius R. In contrast to a previous derivation we also calculate additional terms that are suppressed by factors of frequency over compactification radius. In the limit of a large compactification radius R those terms vanish and the standard result for the non compactified case is recovered.Comment: 17 page

Modeling 3-D objects with planar surfaces for prediction of electromagnetic scattering

Electromagnetic scattering analysis of objects at resonance is difficult because low frequency techniques are slow and computer intensive, and high frequency techniques may not be reliable. A new technique for predicting the electromagnetic backscatter from electrically conducting objects at resonance is studied. This technique is based on modeling three dimensional objects as a combination of flat plates where some of the plates are blocking the scattering from others. A cube is analyzed as a simple example. The preliminary results compare well with the Geometrical Theory of Diffraction and with measured data

Approximating open quantum system dynamics in a controlled and efficient way: A microscopic approach to decoherence

We demonstrate that the dynamics of an open quantum system can be calculated efficiently and with predefined error, provided a basis exists in which the system-environment interactions are local and hence obey the Lieb-Robinson bound. We show that this assumption can generally be made. Defining a dynamical renormalization group transformation, we obtain an effective Hamiltonian for the full system plus environment that comprises only those environmental degrees of freedom that are within the effective light cone of the system. The reduced system dynamics can therefore be simulated with a computational effort that scales at most polynomially in the interaction time and the size of the effective light cone. Our results hold for generic environments consisting of either discrete or continuous degrees of freedom

Laboratory studies on a spherically curved Bragg spectrometer for cosmic X-ray spectroscopy

A spherical array of twenty LiF 200 crystals was built to test the performances of a freestanding, self-focussing spherical crystal cosmic X-ray spectrometer. Measurements presently available show that the size of the image for a point source at infinite distance would be 3 mm (FWHM) along the focalisation axis and 2.1 mm (FWHM) along the dispersion axis. The mosaic spread on individual crystals is less than 0.1 degree. A slightly systematic deviation from the ideal bending (0.1 degree) is observed at the edges of most crystals and this appears to be the major limitation to spectrometer performance

Renormalization group improved black hole space-time in large extra dimensions

By taking into account a running of the gravitational coupling constant with an ultra violet fixed point, an improvement of classical black hole space-times in extra dimensions is studied. It is found that the thermodynamic properties in this framework allow for an effective description of the black hole evaporation process. Phenomenological consequences of this approach are discussed and the LHC discovery potential is estimated.Comment: 13 pages, 6 figure

Event-by-event fluctuations of the charged particle ratio from non-equilibrium transport theory

The event by event fluctuations of the ratio of positively to negatively charged hadrons are predicted within the UrQMD model. Corrections for finite acceptance and finite net charge are derived. These corrections are relevant to compare experimental data and transport model results to previous predictions. The calculated fluctuations at RHIC and SPS energies are shown to be compatible with a hadron gas. Thus, deviating by a factor of 3 from the predictions for a thermalized quark-gluon plasma.Comment: This paper clarifies the previous predictions of Jeon and Koch (hep-ph/0003168) and addresses issues raised in hep-ph/0006023. 2 Figures, 10pp, uses RevTe

In Vivo Evolution of Butane Oxidation by Terminal Alkane Hydroxylases AlkB and CYP153A6

Enzymes of the AlkB and CYP153 families catalyze the first step in the catabolism of medium-chain-length alkanes, selective oxidation of the alkane to the 1-alkanol, and enable their host organisms to utilize alkanes as carbon sources. Small, gaseous alkanes, however, are converted to alkanols by evolutionarily unrelated methane monooxygenases. Propane and butane can be oxidized by CYP enzymes engineered in the laboratory, but these produce predominantly the 2-alkanols. Here we report the in vivo-directed evolution of two medium-chain-length terminal alkane hydroxylases, the integral membrane di-iron enzyme AlkB from Pseudomonas putida GPo1 and the class II-type soluble CYP153A6 from Mycobacterium sp. strain HXN-1500, to enhance their activity on small alkanes. We established a P. putida evolution system that enables selection for terminal alkane hydroxylase activity and used it to select propane- and butane-oxidizing enzymes based on enhanced growth complementation of an adapted P. putida GPo12(pGEc47{Delta}B) strain. The resulting enzymes exhibited higher rates of 1-butanol production from butane and maintained their preference for terminal hydroxylation. This in vivo evolution system could be useful for directed evolution of enzymes that function efficiently to hydroxylate small alkanes in engineered hosts

Leaf Temperatures in a Gas Exchange Chamber and in the Open Air

Leaf temperatures in a Koch fully climatized gas-exchange chamber as designed by Siemens and in a similarly equipped open-air reference were measured with horizontally and vertically inserted thermocouples on Nerium oleander L. On a sunny day with only little air movement and an average air temperature of 20.4 °C, leaf over-temperatures in the gas-exchange chamber were lower on average by 2.2 K. The extent of reduction of over-temperature in the chamber is determined by the reduced global radiation in the chamber and the differences of wind velocities in chamber and reference. Differences in the ventilation intensity in the chamber have no demonstrable influence on the leaf over-temperatures. The over-temperatures of the reference leaves, on the other hand, depend to a large degree on air velocity. The changed radiation and air flow conditions in the chamber as compared with open-air conditions have consequences for the physiological reactions of the enclosed plant and must be taken into account when comparing results from gas-exchange measurements with open-air conditions. For further improvements of gas-exchange measurement equipment, air flow conditions and radiation quantity and quality might be starting point

Observation of Coulomb-Assisted Dipole-Forbidden Intraexciton Transitions in Semiconductors

We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum-well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the $1s$ exciton emission, which we attribute to the terahertz-induced $1s$-to-$2p$ excitation. Simultaneously, a pronounced enhancement of the $2s$-exciton emission is observed, despite the $1s$-to-$2s$ transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2$s$ and 2$p$ states, yielding an effective terahertz transition between the 1$s$ and 2$s$ populations.Comment: 5 pages, 3 figure