396 resultados para Pure state
Resumo:
The British government's response to the London bombings sought to make the terror of that day foreign, even though it appeared largely domestic. This helped construct it as unusual, contingent, part of the uncontrollable ‘otherness’ of the ‘foreign’. However, it also drew the response into the arena of British foreign policy, where the ‘failing state’ has been the dominant conceptualisation of insecurity and terrorism, especially since September 11th. When the bombings are examined through the ‘failing state’ disturbing and important problems are uncovered. Primarily, the ‘failing state’ discourse deconstructs under the influence of the terrorism in London, revealing that Britain itself is a ‘failing state’ by its own description and producing a generalisation of state ‘failure’. It thereby reveals several possible sites for responding to and resisting the government's representation.
Resumo:
We propose a scheme for the determination of the coupling parameters in a chain of interacting spins. This requires only time-resolved measurements over a single particle, simple data postprocessing and no state initialization or prior knowledge of the state of the chain. The protocol fits well into the context of quantum-dynamics characterization and is efficient even when the spin chain is affected by general dissipative and dephasing channels. We illustrate the performance of the scheme by analyzing explicit examples and discuss possible extensions.
Resumo:
Political commentators often cast religious con? ict as the result of the numerical growth and political rise of a single faith. When Islam is involved, arguments about religious fundamentalism are quick to surface and often stand as an explanation in their own right. Yet, as useful as this type of explanation may be, it usually fails to address properly, if at all, two sets of important issues. It avoids, Ž rst, the question of the rise of other religions and their contribution to tensions and con? icts. Second, it reduces the role of the State to a reactive one. The State becomes an object of contest or conquest, or it is simply ignored. Adopting a different approach, this article investigates a controversy that took place in Mozambique in 1996 around the ‘ofŽ cialisation’ of two Islamic holidays. It looks at the role played by religious competition and state mediation. The article shows that the State’s abandonment of religious regulation – the establishment of a free ‘religious market’ – fostered religious competition that created tensions between faiths. It suggests that strife ensued because deregulation was almost absolute: the State did not take a clear stand in religious matters and faith organisations started to believe that the State was becoming, or could become, confessional. The conclusion discusses theoretical implications for the understanding of religious strife as well as Church and State relations. It also draws some implications for the case of Mozambique more speciŽ cally, implications which should have relevance for countries such as Malawi, Zambia and Zimbabwe where problems of a similar nature have arisen.
Resumo:
We have measured the densities of 1s5 and 1s3 argon metastables as a function of the abundance of molecular oxygen in an inductively coupled plasma (ICP) in mixtures of Ar and O2. Laser absorption spectroscopy was used to determine the densities of the metastables. It was found that even small abundances of oxygen lead to large increases in metastable density, mostly due to the reduction in the electron number density, since electron-induced quenching determines the metastable density. At abundances higher than 7% to 15% for powers between 50 and 150W, quenching by oxygen molecules begins to dominate and the metastable density drops again.
Resumo:
Solid-state NMR and TEM were used to quantitatively examine the evolution of clay morphology upon equibiaxial stretching of polypropylene/montmorillonite (PP-MMT) nanocomposites up to a stretch ratio (?= final length/initial length) of 3.5. 1 H spin-lattice relaxation times were measured by the saturation-recovery sequence. For the nanocomposites, initial portions of the magnetization recovery
curves (e~20 ms) were found to depend on v t, indicative of diffusion-limited relaxation and in agreement with calculations based on estimates of the spin-diffusion barrier radius surrounding the paramagnetic centers in the clay, the electron-nucleus coupling constant, and the spin-diffusion coefficient. Initial slopes of these magnetization recovery curves directly correlated with the fraction of clay/polymer interface. New clay surface was exposed as a near linear function of strain. Long-time portions of the magnetization recovery curves yielded information on the average interparticle separations, which decreased slowly before reaching a plateau at ?=~2.5 as particles aligned. TEM images supported these findings and were used to define and quantify degrees of exfoliation and homogeneity from the NMR data. Exfoliation, defined as (platelets/ stack)-1, increased from 0.38 (unstretched) to 0.80 at ? = 3.5 for PP-MMT nanocomposites stretched at
150 C and 16 s-1. A lower stretch temperature, 145 C, which is slightly below melting onset, led to an exfoliation degree of 0.87 at ?= 2.8, consistent with the ability of higher melt viscosities to allow for higher shear stress transfer. Exposure of new clay surface is attributed to aggregate breakup and orientation at low strains (? e ~2) and to platelets sliding apart at higher strains.
Resumo:
The kinetics of the water-gas shift reaction Were Studied on a 0.2% Pt/CeO2 catalyst between 177 and 300 degrees C over a range of CO and steam pressures. A rate decrease with increasing partial pressure of CO was experimentally observed over this sample, confirming that a negative order in CO can occur under certain conditions at low temperatures. The apparent reaction order of CO measured at 197 degrees C was about -0.27. This value is significantly larger than that (i.e, -0.03) reported by Ribeiro and co-workers [A.A. Phatak, N. Koryabkina, S. Rai, J.L. Ratts, W. Ruettinger, R.J. Farrauto, G.E. Blau, W.N. Delgass, F.H. Ribeiro, Catal. Today 123 (2007) 224] at a similar temperature. A kinetic peculiarity was also evidenced, i.e. a maximum of the reaction rate as a function of the CO concentration or possibly a kinetic break, which is sometimes observed in the oxidation of simple molecules. These observations support the idea that competitive adsorption of CO and H2O play an essential role in the reaction mechanism. (C) 2008 Elsevier B.V. All rights reserved.