N* resonance parameters and K-matrix fits to the reactions πN→Δπ+ϱN+ɛN

From a partial wave analysis of the reaction πN→ππN we extract 50 cuoplings and partial widths for N^* resonance decaying into Δπ, ?N and εN. Three different methods of determining the resonance parameters are compared. The signs of the πΔ couplings are found to be consistent with the predictions of l-broken SU(6)_w, if one assigns P′₁₁(1415), P″₁₁(1730) and P₃₃(1700) to [56, L=0⁺] supermultiplets. The signs of the ?N couplings are inconsistent with SU(6)_w symmetry in its l-broken form, but in good agreement with the observed photon couplings.     

Generation of continuously tunable IR radiation by means of difference-frequency mixing of nitrogen-laser and dye-laser radiation in LiIO3

The paper describes the generation of difference frequencies from nitrogen-laser and dye-laser radiation in LiIO₃ which was accomplished for the first time. IR radiation in the range from 0.7 to 2.2 μm is generated, the radiant power being in the watt range. Comparison measurements in LiIO₃, ADP and KDP indicate the benefits of LiIO₃. An analysis of the influence of the bandwidth on the conversion efficiency shows that below 2 μm an efficient wideband transformation is also possible. Experimentally, it was possible to realize IR radiation with bandwidths of 90 Å. Possibilities of improving the efficiency of transformation are discussed.     

Relativistic Linear Spacetime Transformations Based on Symmetry

Usually the Lorentz transformations are derived from the conservation of the spacetime interval. We propose here a way of obtaining spacetime transformations between two inertial frames directly from symmetry, the isotropy of the space and principle of relativity. The transformation is uniquely defined except for a constant e, that depends only on the process of synchronization of clocks inside each system. Relativistic velocity addition is obtained, and it is shown that the set of velocities is a bounded symmetric domain. If e=0, Galilean transformations are obtained. If e>0, the speed 1/e and a spacetime interval are conserved. By assuming constancy of the speed of light, we get e=1/c ² and the transformation between the frames becomes the Lorentz transformation. If e<0, a proper speed and a Hilbertian norm are conserved.     

Experimental implementation of the quantum baker's map

This Letter reports on the experimental implementation of the quantum baker's map via a three bit nuclear magnetic resonance quantum information processor. The experiments tested the sensitivity of the quantum chaotic map to perturbations. In the first experiment, the map was iterated forward and then backward to provide benchmarks for intrinsic errors and decoherence. In the second set of experiments, the least significant qubit was perturbed in between the iterations to test the sensitivity of the quantum chaotic map to controlled perturbations. These experiments can be used to investigate existing theoretical predictions for quantum chaotic dynamics.     

Border between regular and chaotic quantum dynamics

We identify a border between regular and chaotic quantum dynamics. The border is characterized by a power-law decrease in the overlap between a state evolved under chaotic dynamics and the same state evolved under a slightly perturbed dynamics. For example, the overlap decay for the quantum kicked top is well fitted with [1+(q-1)(t/tau)2](1/(1-q)) (with the nonextensive entropic index q and tau depending on perturbation strength) in the region preceding the emergence of quantum interference effects. This region corresponds to the edge of chaos for the classical map from which the quantum chaotic dynamics is derived.     

Parameter Estimation and the CRLB with Uncertain Origin Measurements

Parameter estimation in the presence of false measurements due to false alarms and missed true detections, i.e., in the presence of measurement origin uncertainty, is a difficult problem because of the need for data association, the process of deciding which, if any, is the true measurement and which are false. An additional aspect of estimation is performance evaluation via, for example, the Cramer-Rao Lower Bound (CRLB), which quantifies the achievable performance. With measurement origin uncertainty and the ensuing data association, the CRLB has to be modified to account for the loss of information due to false alarms and missed true detections. This is the focus of our paper—we show that the loss of information can be accounted for by a single scalar, known as the information reduction factor, under certain conditions. We illustrate the evaluation of the generalized CRLB on parameter estimation from direction-of-arrival measurements with applications to target tracking, communications and signal processing. Simulation results on a realistic scenario show that the lower bounds quantified via the information reduction factor are statistically compatible with the observed errors.     

A clinical study of failure in microchannel cooled diodes used in large laser systems

In this paper we investigate the source of failure in commercial, microchannel cooled CW diode bars placed in 12 bar horizontal arrays. The arrays were used to pump Nd:YAG rods in our 10 kW developmental laser. The laser was operated at low duty factor over a period of over 2 years. Experimental evidence indicated that the sudden, catastrophic failure was because of degraded cooling. We used optical microscopes, an X-ray microfocus imager, and a thermal neutron scattering camera to look inside the microcoolers. Our investigations revealed only one possible failure mechanism: cooling flow reduction because of delamination of the Au coating the walls of the microcoolers and the entrapment of Au flakes within the microchannel structures. We observed blisters in the microcoolers under working bars, and flake-like structures in the microcoolers under burnt-out bars (all taken from the laser). We observed no evidence of either massive blockages because of electrochemical deposits, or of corrosion/erosion in the microchannel walls. Integral operation times of the high flow-rate cooling system and of the diodes themselves were too short by one and two orders of magnitude, respectively, to explain the observed failures. Microchannel immersion times in the deionized water were, however, long enough to allow for corrosion of metals that may have been exposed through defects in the Au coatings. Three-dimensional heat flow simulations showed that blockage of multiple microchannels towards the edge of a bar can easily lead to catastrophic temperature increases.     

High‐Z Nanostructured Ceramics in Radiotherapy: First Evidence of Ta2O5‐Induced Dose Enhancement on Radioresistant Cancer Cells in an MV Photon Field

This article pioneers a study into the use of the tantalum pentoxide nanoceramics as novel candidates for dose enhancement radiotherapy. It is revealed that a significant induced dose enhancement on radioresistant cancer cells expose to tantalum pentoxide nanoparticles and irradiated with 10 MV. In this study, in vitro experiments are performed. The radiobiological endpoint is clonogenic survival. We exposed 9L gliosarcoma cells to the nanoparticles at 50–500 μg mL^?1 range and observed concentration‐dependent toxicity. Irradiation of the exposed and unexposed cells with 10 MV X‐ray photons reveals a sensitization enhancement ratio of 1.33. The associated cell survival curves demonstrate a significant change in shape, indicative of increased lethality of the local radiation environment. We postulate that this enhancement is primarily due to secondary electrons produced from photoelectric interaction and pair production, with backscattering on nanoparticle aggregates leading to increased radiobiological effectiveness.