39 resultados para Combustível nuclear


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Discusses deterrence theory in relation to the nuclear armed nations. Suggests the world may turn from the deterrence of war using nuclear weapons to deterring countries and other oganisations from their acquisition.

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Preliminary results are presented on the correlation between enhanced solvent mobility and ionic conductivity in plasticized polyether–urethane solid polymer electrolytes using 13C nuclear magnetic resonance spectroscopic spin–lattice relaxation time measurements to probe polymer mobility.

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13C nuclear magnetic resonance (n.m.r.) has been used to study polypyrrole and N-substituted polypyrrole in the solid state. The extent of oxidation appears to be counterion-dependent; in particular, the quinoid structure appears favoured in the films prepared with dodecyl sulfate. Resonances associated with the quinoid unit are lost upon reduction of the polypyrrole film, which supports the idea that the quinoid structure is associated with the oxidized form of polypyrrole. N-substituted polypyrroles have a more distinct resonance at 110 ppm, which is linked to lower degrees of oxidation or charge delocalization in these systems. The decrease in conductivity of polypyrrole upon thermal ageing in air is associated with both the loss of counterion (‘thermal dedoping’) and the decomposition of the quinoid structure in the polymer backbone. There is no indication of carbonyl formation in the solid-state n.m.r. spectra obtained in the present study.

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Nuclear magnetic resonance (NMR) is a technique that allows the probing of the dynamics of specific magnetically active nuclei. In the present study a polyethylene glycol network containing varying concentrations of LiClO4 have been studied using 7Li NMR relaxation techniques. A plasticiser, tetraglyme, has been added to several samples to improve the mobility of the polymer and thus of the ionic species. The effects of tetraglyme and salt concentration on the cationic mobility and environment have been investigated using T1 and T2 relaxation experiments, with the presence of two cationic species of differing relaxation times (and possibly mobility) reported. The results are discussed with relevance to conductivity measurements made on similar samples.

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China's profile in the nuclear nonproliferation regime is changing at a crucial time. The regime is under considerable internal and external strain as a result of eroding international support and trends in vertical and horizontal nuclear proliferation. While China's nonproliferation agenda and approach differ in some respects from those of other key actors, the gap separating China from the established drivers of efforts to address horizontal nuclear proliferation in terms of the objectives, institutions, and approach of the nonproliferation regime is diminishing, and there is considerable potential for China to contribute to the capacity of the regime to adapt to changing requirements. The Asia-Pacific region features both as the area of greatest nonproliferation concern to China and as the area where proliferation concerns are most likely to spur the further qualitative development of Chinese nonproliferation policy.

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This volume in the Documents on Australian Foreign Policy series draws on unpublished records from the National Archives of Australia to document the negotiation of the Nuclear Non-Proliferation Treaty (NPT) from an Australian perspective. Commencing with early post-war efforts to control nuclear energy following the dropping of atomic bombs on Hiroshima and Nagasaki, the volumes traces Australia’s changing attitude to the issue of nuclear arms control and disarmament during the Cold War years of the 1950s and 1960s and its ambiguous approach to the acquisition of nuclear weapons in the subsequent negotiation of the NPT. Signed by the Gorton government in 1970 after considerable debate in the policymaking community in Canberra, the treaty was ratified by the Whitlam government in 1973 and has since formed a fundamental plank in Australian attitudes and policies towards international efforts to reduce and eventually eliminate nuclear weapons.