Theoretical studies of product polarization and state distributions of the H+HCl reaction

The angular momentum polarization and rotational state distributions of the H-2 and HCl products from the H + HCl reaction are calculated at a relative translational energy of 1.6 eV by using quasiclassical trajectories on two potential energy surfaces, one from G3 surface [T.C. Allison et al., J. Phys. Chem. 100 (1996) 13575], and the other from BW2 surface [W. Bian, H.-J. Werner, J. Chem. Phys. 112 (2000) 220]. Product rotational distributions obtained on the G3 potential energy surface (PES) are much closer to the experimental results (P.M. Aker et al., J. Chem. Phys. 90 (1989) 4795; J. Chem. Phys. 90 (1989) 4809) than the distributions calculated on the BW2 PES. The distributions of P(phi(r)) for the H-2 and HCl products obtained on the G3 PES are similar, whereas the rotational alignment effect of the H-2 product is stronger than that of the HCl product. In contrast to the polarization distributions obtained on the G3 PES, the rotational alignment effect of the two products calculated on the BW2 PES is similar. However, the abstraction reaction is dominated by out-of-plane mechanisms, while the exchange reaction is dominated by in-plane mechanisms. The significant difference of the product rotational polarization obtained on the G3 and BW2 PESs implies that the studies of the dynamical stereochemistry can provide a sensitive test for the accuracy of the PES. (C) 2002 Elsevier Science B.V. All rights reserved.

Archbishop William King (1650-1729) and the Constitution of Church and State

Accepted Version

Birth-death processes with mass annihilation and state-dependent immigration

A birth-death process is subject to mass annihilation at rate β with subsequent mass immigration occurring into state j at rateα j . This structure enables the process to jump from one sector of state space to another one (via state 0) with transition rate independent of population size. First, we highlight the difficulties encountered when using standard techniques to construct both time-dependent and equilibrium probabilities. Then we show how to overcome such analytic difficulties by means of a tool developed in Chen and Renshaw (1990, 1993b); this approach is applicable to many processes whose underlying generator on E\{0} has known probability structure. Here we demonstrate the technique through application to the linear birth-death generator on which is superimposed an annihilation/immigration process.

An ontological characterization of time-series and state-sequences for data mining

Time-series and sequences are important patterns in data mining. Based on an ontology of time-elements, this paper presents a formal characterization of time-series and state-sequences, where a state denotes a collection of data whose validation is dependent on time. While a time-series is formalized as a vector of time-elements temporally ordered one after another, a state-sequence is denoted as a list of states correspondingly ordered by a time-series. In general, a time-series and a state-sequence can be incomplete in various ways. This leads to the distinction between complete and incomplete time-series, and between complete and incomplete state-sequences, which allows the expression of both absolute and relative temporal knowledge in data mining.

The 1996 ‘Muslim holiday’ affair. Religious competition and state mediation in contemporary Mozambique

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.

Devolution and party organizational change: The British and Spanish and state-wide parties compared

This article investigates the link between regionalization of the structure of government, regional elections and regionalism on the one hand, and the organization of state-wide political parties in Spain and the UK on the other. It particularly looks at two aspects of the relations between the central and regional levels of party organization: integration of the regional branches in central decision making and autonomy of the regional branches. It argues that the party factors are the most crucial elements explaining party change and that party leaders mediate between environmental changes and party organization. The parties' history and beliefs and the strength of the central leadership condition their ability or willingness to facilitate the emergence of meso-level elites. The institutional and electoral factors are facilitating factors that constitute additional motives for or against internal party decentralization

Changing climate, changing process: implications for salt transportation and weathering within building sandstones in the UK

Salt weathering is a crucial process that brings about a change in stone, from the scale of landscapes to stone outcrops and natural building stone facades. It is acknowledged that salt weathering is controlled by fluctuations in temperature and moisture, where repeated oscillations in these parameters can cause re-crystallisation, hydration/de-hydration of salts, bringing about stone surface loss in the form of, for example, granular disaggregation, scaling, and multiple flaking. However, this ‘traditional’ view of how salt weathering proceeds may need to be re-evaluated in the light of current and future climatic trends. Indeed, there is considerable scope for the investigation of consequences of climate change on geomorphological processes in general. Building on contemporary research on the ‘deep wetting’ of natural building stones, it is proposed that (as stone may be wetter for longer), ion diffusion may become a more prominent mechanism for the mixing of molecular constituents, and a shift in focus from physical damage to chemical change is suggested. Data from ion diffusion cell experiments are presented for three different sandstone types, demonstrating that salts may diffuse through porous stone relatively rapidly (in comparison to, for example, dense concrete). Pore water from stones undergoing diffusion experiments was extracted and analysed. Factors controlling ion diffusion
relating to ‘time of wetness’ within stones are discussed, (continued saturation, connectivity of pores, mineralogy, behaviour of salts, sedimentary structure), and potential changes in system dynamics as a result of climate change are addressed. System inputs may change in terms of increased moisture input, translating into a greater depth of wetting front. Salts are likely to be ‘stored’ differently in stones, with salt being in solution for longer periods (during prolonged winter wetness). This has myriad implications in terms of the movement of ions by diffusion and the potential for chemical change in the stone (especially in more mobile constituents), leading to a weakening of the stone matrix/grain boundary cementing. The ‘output’ may be mobilisation and precipitation of elements leading to, for example, uneven cementing in the stone. This reduced strength of the stone, or compromised ability of the stone to absorb stress, is likely to make crystallisation a more efficacious mechanism of decay when it does occur. Thus, a delay in the onset of crystallisation while stonework is wet does not preclude exaggerated or accelerated material loss when it finally happens.