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

Photosynthesis can be enhanced by lateral CO 2

This study examines the extent to which lateral gas diffusion can influence intercellular CO(2) concentrations (c(i)) and thus photosynthesis in leaf areas with closed stomata. Leaves were partly greased to close stomata artificially, and effects of laterally diffusing CO(2) into the greased areas were studied by gas-exchange measurement and chlorophyll fluorescence imaging. Effective quantum yields (Delta F/F(m)') across the greased areas were analysed with an image-processing tool and transposed into c(i) profiles, and lateral CO(2) diffusion coefficients (D(C'lat)), directly proportional to lateral conductivities (), were estimated using a one-dimensional (1D) diffusion model. Effective CO(2) diffusion distances in Vicia faba (homobaric), Commelina vulgaris (homobaric) and Phaseolus vulgaris (heterobaric) leaves clearly differed, and were dependent on D(C'lat), light intensity, [CO(2)], and [O(2)]: largest distances were approx. 7.0 mm for homobaric leaves (with high D(C'lat)) and approx. 1.9 mm for heterobaric leaves (low D(C'lat)). Modeled lateral CO(2) fluxes indicate large support of photosynthesis over submillimeter distances for leaves with low D(C'lat), whereas in leaves with large D(C'lat), photosynthesis can be stimulated over distances of several millimeters. For the plant species investigated, the surplus CO(2) assimilation rates of the greased leaf areas (A(gr)) differed clearly, depending on lateral conductivities of the respective leaves

Aetiology and clinical features of dentine hypersensitivity

Dentine hypersensitivity (DH) is a common oral condition, which is typically short lasting, an intense pain located around teeth and often associated with cold stimuli. An innate problem with DH is that its clinical features are transient and patients do not always present with DH at examination, even though they may suffer from it regularly. Indeed, the nature of DH appears to be cyclic and most sufferers self-medicate and use desensitising toothpastes to control the condition. There are increasing suggestions from the published literature of DH supporting the transient nature of the condition. The reasons for this trend, historically, have been unclear. Indeed, the cause/s of DH have been poorly understood and resulted in DH being termed an enigma 32 years ago, and this concept has been revisited on a number of occasions. The apparent historical lack in the understanding of the aetiological processes in particular tooth wear often resulted in elusive treatment and preventive strategies which focused on the symptoms of DH rather than its cause/s. Nevertheless, our understanding of the condition is somewhat clearer today. This chapter therefore focuses attention on the clinical features of DH and in detail on the causes of DH and the associated clinical presentation