Lawson criterion for ignition exceeded in an inertial fusion experiment

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

Neural processing of natural sounds

Natural sounds include animal vocalizations, environmental sounds such as wind, water and fire noises and non-vocal sounds made by animals and humans for communication. These natural sounds have characteristic statistical properties that make them perceptually salient and that drive auditory neurons in optimal regimes for information transmission.Recent advances in statistics and computer sciences have allowed neuro-physiologists to extract the stimulus-response function of complex auditory neurons from responses to natural sounds. These studies have shown a hierarchical processing that leads to the neural detection of progressively more complex natural sound features and have demonstrated the importance of the acoustical and behavioral contexts for the neural responses.High-level auditory neurons have shown to be exquisitely selective for conspecific calls. This fine selectivity could play an important role for species recognition, for vocal learning in songbirds and, in the case of the bats, for the processing of the sounds used in echolocation. Research that investigates how communication sounds are categorized into behaviorally meaningful groups (e.g. call types in animals, words in human speech) remains in its infancy.Animals and humans also excel at separating communication sounds from each other and from background noise. Neurons that detect communication calls in noise have been found but the neural computations involved in sound source separation and natural auditory scene analysis remain overall poorly understood. Thus, future auditory research will have to focus not only on how natural sounds are processed by the auditory system but also on the computations that allow for this processing to occur in natural listening situations.The complexity of the computations needed in the natural hearing task might require a high-dimensional representation provided by ensemble of neurons and the use of natural sounds might be the best solution for understanding the ensemble neural code

Characterization of 15N-TNT residues after an anaerobic/aerobic treatment of soil/molasses mixtures by solid-state 15N NMR spectroscopy. 1. Determination and optimization of relevant NMR spectroscopic parameters

7 pages, 4 figures, 4 tables, 25 references.Solid-state 15N NMR was applied to a humic acid, extracted from 15N-2,4,6-trinitrotoluene (TNT) enriched soil treated in an anaerobic/aerobic composting system to characterize the nitrogen functionality of the transformation products bound to the soil organic material. Signals assignable to aniline derivatives and condensation products were identified, indicating that the anaerobic/aerobic treatment caused a reduction of nitro groups followed by condensation reactions with the soil organic material. Relevant parameters for routine application of the cross polarization magic angle spinning technique were determined and optimized. The proton spin-lattice relaxation times of all peaks in the 15N NMR spectrum of the humic acid did not exceed 30 ms. Due to the fast relaxation, the application of 15N NMR spectroscopy to soils with lower enrichment of 15N-TNT is feasible. The influence of spinning sidebands on the intensity distribution was shown to be minimal at spinning speeds between 5.5 and 6.5 kHz. Contact times between 0.7 and 1 ms resulted in spectra with representative intensity distribution of all visible 15N-TNT transformation products. However an underestimation of unreacted TNT must be considered. The results imply that CPMAS 15N NMR is a valuable tool for the examination of bound residues of TNT in soils. (Figure 1).This work was supported by the Federal Ministry of Education, Science, Research and Technology (BMBF), by the state of Lower Saxony and the Industrieverwaltungsgesellschaft AG(IVG), Bonn, Germany.Peer reviewe

Characterization of 15N-TNT residues after an anaerobic/aerobic treatment of soil/molasses mixtures by solid-state 15N NMR spectroscopy. 2. Systematic investigation of whole soil and different humic fractions

8 pages, 6 figures, 2 tables, 42 references.An anaerobic/aerobic composting experiment with 15N-2,4,6-trinitrotoluene (TNT) spiked soil was performed to investigate the fate of the explosive under the applied conditions. For a qualitative description of TNT-residues formed during the composting process, bulk soil and different soil fractions were subjected to solid-state 15N NMR spectroscopy. Major resonance signals could be detected in the chemical shift regions of five-ring heterocyclic nitrogen and in the area of aniline derivatives and primary amines. Distinct nitro peaks were found in the bulk samples and in the humic fractions obtained with a mild extraction procedure. This signal disappeared in the material extracted with a more drastic procedure. Quantitative investigations of the 15N distribution in the composted material revealed that 33% of the stable nitrogen isotope was incorporated into the humic- and fulvic acid, and 23% was present in the humin. Furthermore 38.8% of the 15N present in the composted material could be allotted to condensed TNT residues, whereas 1.9% are assigned to nitro functions and 15.2% to amino functions. In the investigation presented here a bioremediation method was simulated with 15N-TNT spiked soil. The nonradioactive label allowed a qualitative and quantitative characterization of residues of the explosive. Our results give strong evidence for a stable incorporation of the nitroaromatics into the humic material of soils. However, further investigations will be necessary to prove a long-time stability of bound TNT residues and to assess toxicological effects of the treated soil.This work was supported by the Federal Ministry of Education, Science, Research and Technology (BMBF), by the state Lower Saxony and the Industrieverwaltungsgesellschaft AG (IVG), Bonn, Germany.Peer reviewe