Pediatric Kennedy Terminal Ulcer

Photograph of Fossett's circus loads, 2 AEC Matadors - KKN412 - and trailers, taken Forest site, 28 September 1959 whole side view

Financial intermediation and the role of price discrimination in a two-tier market

Though unambiguously outperforming all other financial markets in terms of liquidity, foreign exchange trading is still performed in opaque and decentralized markets. In particular, the two-tier market structure consisting of a customer segment and an interdealer segment to which only market makers have access gives rise to the possibility of price discrimination. We provide a theoretical foreign exchange pricing model that accounts for market power considerations and analyze a database of the trades of a German market maker and his cross section of end-user customers. We find that the market maker generally exerts low bargaining power vis-á-vis his customers. The dealer earns lower average spreads on trades with financial customers than commercial customers, even though the former are perceived to convey exchange-rate-relevant information. From this perspective, it appears that market makers provide interdealer market liquidity to end-user customers with cross-sectionally differing spreads. --foreign exchange,market microstructure,pricing behavior

Thermoluminescence fading studies: Implications for long-duration space measurements in Low Earth Orbit

Within a 1.5 year comprehensive fading experiment several batches of LiF:Mg,Ti and LiF:Mg,Cu,P thermoluminescence detectors (TLDs) were studied. The TLDs originated from two manufacturers and were processed by three laboratories using different annealing and readout conditions. The TLDs were irradiated with two radiation modalities (gamma-rays and thermal neutrons) and were stored at two temperatures (-17.4C and +18.5C). The goal of the experiment was to verify the stability of TLDs in the context of their application in long-term measurements in space. The results revealed that the response of all TLDs is stable within 10% for the studied temperature range. No influence of the radiation type was found. These results indicate that for the properly oven-annealed LiF TLDs, fading is not a significant problem, even for measuring periods longer than a year

Coherence properties of nanofiber-trapped cesium atoms

We experimentally study the ground state coherence properties of cesium atoms in a nanofiber-based two-color dipole trap, localized 200 nm away from the fiber surface. Using microwave radiation to coherently drive the clock transition, we record Ramsey fringes as well as spin echo signals and infer a reversible dephasing time $T_2^\ast=0.6$ ms and an irreversible dephasing time $T_2^\prime=3.7$ ms. By theoretically modelling the signals, we find that, for our experimental parameters, $T_2^\ast$ and $T_2^\prime$ are limited by the finite initial temperature of the atomic ensemble and the heating rate, respectively. Our results represent a fundamental step towards establishing nanofiber-based traps for cold atoms as a building block in an optical fiber quantum network

Translations and dynamics

We analyze the role played by local translational symmetry in the context of gauge theories of fundamental interactions. Translational connections and fields are introduced, with special attention being paid to their universal coupling to other variables, as well as to their contributions to field equations and to conserved quantities.Comment: 22 Revtex pages, no figures. Published version with minor correction

Back-Scattering Properties of a Waveguide-Coupled Array of Atoms in the Strongly Non-Paraxial Regime

We experimentally investigate the back-scattering properties of an array of atoms that is evanescently coupled to an optical nanofiber in the strongly non-paraxial regime. We observe that the power and the polarization of the back-scattered light depend on the nanofiber-guided excitation field in a way that significantly deviates from the predictions of a simple model based on two-level atoms and a scalar waveguide. Even though it has been widely used in previous experimental and theoretical studies of waveguide-coupled quantum emitters, this simple model is thus in general not adequate even for a qualitative description of such systems. We develop an ab initio model which includes the multi-level structure of the atoms and the full vectorial properties of the guided field and find very good agreement with our data

Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber

Trapping and optically interfacing laser-cooled neutral atoms is an essential requirement for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multi-color evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices

The ALTCRISS project on board the International Space Station

The Altcriss project aims to perform a long term survey of the radiation environment on board the International Space Station. Measurements are being performed with active and passive devices in different locations and orientations of the Russian segment of the station. The goal is to perform a detailed evaluation of the differences in particle fluence and nuclear composition due to different shielding material and attitude of the station. The Sileye-3/Alteino detector is used to identify nuclei up to Iron in the energy range above 60 MeV/n. Several passive dosimeters (TLDs, CR39) are also placed in the same location of Sileye-3 detector. Polyethylene shielding is periodically interposed in front of the detectors to evaluate the effectiveness of shielding on the nuclear component of the cosmic radiation. The project was submitted to ESA in reply to the AO in the Life and Physical Science of 2004 and data taking began in December 2005. Dosimeters and data cards are rotated every six months: up to now three launches of dosimeters and data cards have been performed and have been returned with the end of expedition 12 and 13.Comment: Accepted for publication on Advances in Space Research http://dx.doi.org/10.1016/j.asr.2007.04.03